 
 
 
   
  
 
 
 
 
 
 
 
 
  
 
 ICS 93.025, 23.040.20, 23.040.45     DMS 374 -1:2021  
Second edition  
ISO 4427 -1:2019  
IDT 
 
 
 
DRAFT MALAWI STANDARD  
 
 
 
 
 
 
 
 
 
 
 
 
Plastics piping systems — 
Polyethylene (PE) pipes and fittings for 
water supply —  
Part 1 : General  
 
 
 
 
 
 
 
 
 
 
 
 
 
NOTE: This is a Draft Malawi Standard  and should not be regarded or used as a Malawi Standard  
__________________  
 Published by  
MALAWI  STANDARDS BOARD   
 
  
 
 ICS 93.025, 23.040.20, 23.040.45     DMS 374 -1:2021  
Second edition  
ISO 4427 -1:2019  
IDT 
 
 
 
 
 
 
Plastics piping systems — Polyethylene 
(PE) pipes and fittings for water supply —  
Part 1 : General  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Obtainable from the  
Malawi Bureau of Standards  
P O Box  946 
BLANTYRE  
 
Tel: +265 1 870 488  
Fax: +265 1 870 756  
E-mail: mbs@mbsmw.org   
Website: www.mbsmw.org   
Price based on 14 pages  
© Copyright reserved   
 
  
  
 
i 
 TABLE OF CONTENTS  
 
Contents  ................................ ................................ ................................ ................................ ...................  Page  
Foreword  ................................ ................................ ................................ ................................ ....................   i 
Introduction  ................................ ................................ ................................ ................................ ................   i 
Scope  ................................ ................................ ................................ ................................ .........................   1 
Normative references  ................................ ................................ ................................ ................................   1 
Terms and definitions  ................................ ................................ ................................ ................................   3 
Symbols and abbreviated terms  ................................ ................................ ................................ ................   6 
Material  ................................ ................................ ................................ ................................ ......................   7 
Effects on water quality ................................ ................................ ................................ ..............................   11 
Annex A (informative) Pressure reduction coefficient  ................................ ................................ ...............   12 
Annex B (informative) Resistance to rapid crack pr opagation  ................................ ................................ ..  13 
Bibliography  ................................ ................................ ................................ ................................ ...............   14 
 
 
FOREWORD  
 
This Malawi Standard is a review of MS 374 -1:1992, Black polyethylene pipes for the conveyance of liquids  - 
Specification. Part 1: Low  density polyethylene pressure pipes . 
 
This Draft Malawi Standard  is identical  to the international standard, ISO 4427 -1: 2019  Plastics piping systems 
— Polyethylene (PE) pipes a nd fittings for water supply — Part 1: General  
 
Acknowledgement is made for the use of the above standard.  
 
 
INTRODUCTION  
 
The DMS 374  series of standards are a set of system standards that specify the requirements for a piping 
system and its components when made from polyethylene (PE). The piping system is intended to be used in 
buried or above ground applications, for the conveyance of  water for human consumption, raw water prior to 
treatment, drainage and sewerage under pressure, vacuum sewer systems, and water for other purposes.  
 
In respect of potential adverse effects on the quality of water intended for human consumption caused by the 
products covered by the DMS 374  series, it does not provide information on the restriction on the use of 
products.  
 
NOTE  - Guidance for assessment of conformity can be found in Reference [ 2] in the Bibliography.  
 
 
TECHNICAL COMMITTEE  
 
This Draft Malawi Standard was developed by the Technical Committee MBS/TC 2 Pipes and fittings  and the 
following companies and organisations  were represented : 
 
Blantyre City Council;  
Blantyre Water Board;  
Flowtech Limited;  
Lilongwe Water Board;  
Malawi University of Business and Applied Sciences;  
Ministry of Forestry and Natural Resources;  
O.G. Plastics Limited;   
 
ii 
 Ruo Consultants; and  
Southern Region Water Board  
 
 
NOTICE  
 
This Draft Malawi Standard shall be revi ewed every five years, or earlier  when  it is necessary  in order to keep 
abreast of progress.  Comments are welcome and shall be  considered when the standard  is being  reviewed .  
 
  
  
 
1 
 DMS 374-1:2021 
DRAFT MALAWI STANDARD  
Plastics piping systems — Polyethylene (PE) pipes and 
fittings for water supply —  
Part 1: General  
 
 
1 SCOPE  
 
This document specifies the general aspects of polyethylene (PE) compounds for the manufacture of pressure 
pipes and fittings (mains and service pipes) for buried or above ground applications, intended for the 
conveyance of:  
 
— water for human consumption;  
 
— raw water prior to treatment;  
 
— drainage and sewerage under pressure;  
 
— vacuum sewer systems;  
 
— water for other purposes.  
 
This document also specifies the test parameters and requirements for the test methods referred to in this 
document.  
 
In conjunction with other parts of the DMS 374  series, this document is applicable to PE pipes and fittings, 
their joints  and to joints with components made of PE and other materials, intended to be used under the 
following conditions:  
 
a) a maximum allowable operating pressure (PFA) up to and including 25 bar1; 
 
b) an operating temperature of 20 °C as the reference temperature.  
 
NOTE 1  - For other operating temperatures, guidance is given in Annex A.  
 
The DMS 374  series covers a range of maximum allowable operating pressures and gives requirements 
concerning colours.  
 
NOTE 2  - It is the responsibility of the purchaser or specifier to make the appropriate selections from these aspects, taking into account 
their particular requirements and installation practices or codes.  
 
 
2 NORMATIVE REFERENCES  
 
The following standards contain provisions which, through reference in this text, constitute provisions of this 
Draft Malawi S tandard. All standards are subject to revision and, since any reference to a standard is deemed 
to be a reference to the latest ed ition of that standard, parties to agreements based on this Draft Malawi 
Standard are encouraged to take steps to ensure the use of the most recent editions of the standards indicated 
below. Information on currently valid national and international standar ds can be obtained from  the Malawi 
Bureau of Standards . 
 
ISO 3 , Preferred numbers — Series of preferred numbers ; 
ISO 472 , Plastics — Vocabulary ; 
                                                 
1 1 bar = 0 .1 MPa = 105 Pa; 1 MPa = 1 N/mm   
 
2 
 ISO 1043 -1, Plastics — Symbols and abbreviated terms — Part 1: Basic polymers and their special 
characteristics ; 
ISO 1133 -1, Plastics — Determination of the melt mass -flow rate (MFR) and melt volume -flow rate (MVR) of 
thermoplastics — Part 1: Standard method ; 
ISO 1167 -1:2006 , Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination  
of the resistance to internal pressure — Part 1: General method ; 
ISO 1167 -2, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of 
the resistance to internal pressure — Part 2: Preparation of pipe test pieces ; 
ISO 1 183-1, Plastics — Methods for determining the density of non -cellular plastics — Part 1: Immersion 
method, liquid pycnometer method and titration method ; 
ISO 1183 -2, Plastics — Methods for determining the density of non -cellular plastics — Part 2: Density gradient 
column method ; 
ISO 4427 -2, Plastics piping systems for water supply, and for drainage and sewerage under pressure — 
Polyethylene (PE) — Part2: Pipes ; 
ISO 4427 -3, Plastics piping systems for water supply, and for drainage and sewerage under pressur e — 
Polyethylene (PE) — Part 3: Fittings ; 
ISO 6259 -1, Thermoplastics pipes — Determination of tensile properties — Part 1: General test method ; 
ISO 6259 -3, Thermoplastics pipes — Determination of tensile properties — Part 3: Polyolefin pipes ; 
ISO 6964 , Polyolefin pipes and fittings — Determination of carbon black content by calcination and pyrolysis 
— Test method ; 
ISO 9080 , Plastics piping and ducting systems — Determination of the long -term hydrostatic strength of 
thermoplastics materials in pipe form by e xtrapolation ; 
ISO 11357 -6, Plastics — Differential scanning calorimetry (DSC) — Part 6: Determination of oxidation 
induction time (isothermal OIT) and oxidation induction temperature (dynamic OIT) ; 
ISO 11413 , Plastics pipes and fittings — Preparation of te st piece assemblies between a polyethylene (PE) 
pipe and an electrofusion fitting ; 
ISO 11414 , Plastics pipes and fittings — Preparation of polyethylene (PE) pipe/pipe or pipe/fitting test piece 
assemblies by butt fusion ; 
ISO 12162 , Thermoplastics materials  for pipes and fittings for pressure applications — Classification, 
designation and design coefficient ; 
ISO 13477 , Thermoplastics pipes for the conveyance of fluids — Determination of resistance to rapid crack 
propagation (RCP) — Small -scale steady -state t est (S4 test) ; 
ISO 13478 , Thermoplastics pipes for the conveyance of fluids — Determination of resistance to rapid crack 
propagation (RCP) — Full-scale test (FST) ; 
ISO 13479 , Polyolefin pipes for the conveyance of fluids — Determination of resistance to cr ack propagation 
— Test method for slow crack growth on notched pipes ; 
ISO 13953 , Polyethylene (PE) pipes and fittings — Determination of the tensile strength and failure mode of 
test pieces from a butt -fused joint ; 
ISO 13954 , Plastics pipes and fittings — Peel decohesion test for polyethylene (PE) electrofusion assemblies 
of nominal outside diameter greater than or equal to 90 mm ; 
ISO 15512 , Plastics — Determination of water content ; 
ISO 16871 , Plastics piping and ducting systems — Plastics pipes and fittin gs — Method for exposure to direct 
(natural) weathering ; and 
EN 12099 , Plastics piping systems — Polyethylene piping materials and components — Determination of 
volatile content .  
 
3 
 3 TERMS AND DEFINITIONS  
 
For the purposes of this document, the terms and definitions given in ISO 3, ISO 472  and ISO 1043 -1 and the 
following apply.  
 
3.1 Geometrical terms  
 
3.1.1  
nominal size  
DN/OD  
numerical designation of the size of a component related to the outside diameter  
 
Note 1 to entry : It is a convenient round number approximately equal to the manufacturing dimension in millimetres (mm). It is not 
applicable to components designated by thread size.  
 
3.1.2  
nominal outside diameter  
dn 
specified outside diameter assigned to  a nominal size DN/OD  
 
Note 1 to entry : Nominal outside diameter is expressed in millimetres.  
 
3.1.3  
outside diameter at any point  
de 
value of the measurement of the outside diameter through its cross -section at any point of the pipe, rounded 
to the next greater 0 .1 mm  
 
3.1.4  
mean outside diameter  
dem 
value of the measurement of the outer circumference of the pipe or spigot end of a fitting in any cross -section 
divided by π (= 3.142), rounded to the next greater 0 .1 mm  
 
3.1.5  
minimum mean outside diameter  
dem,min 
minimum value for the mean outside diameter as specified for a given nominal size  
 
3.1.6  
maximum mean outside diameter  
dem,max  
maximum value for the mean outside diameter as specified for a given nominal size  
 
3.1.7  
out-of-roundness  
ovality  
difference between the maximum and the minimum outside diameters in the same cross -section of a pipe or 
spigot  
 
3.1.8  
nominal wall thickness  
en 
numerical designation of the wall thickness of a component, which is a convenient round number, 
approximately eq ual to the manufacturing dimension in millimetres (mm)  
 
Note 1 - to entry : For thermoplastics components conforming to the different parts of the DMS 374  series, the value of the nominal wall 
thickness, en, is identical to the specified minimum wall thickness at any point , emin. 
 
3.1.9  
wall thickness at any point  
e 
wall thickness at any point around the circumference of a component rounded to the next greater 0 .1 mm   
 
4 
  
Note 1 to entry : The symbol for the wall thickness of the fittings body at any point is E. 
 
3.1.10  
minimum wall thickness at any point  
emin 
minimum value for the wall thickness at any point around the circumference of a component, as specified  
 
3.1.11  
maximum wall thickness at any point  
emax 
maximum value for the wall thickness at any point around the circumference of a component, as specified  
 
3.1.12  
mean wall thickness  
em 
arithmetical mean of a number of measurements of the wall thickness, regularly spaced around the 
circumference and in the same cross -section of a component, including the measured minimum and the 
measured maximum values of the wall thickness in that cross -section  
 
3.1.13  
pipe series  
S 
dimensionless number for pipe designation conforming to ISO 406 5 
 
Note 1 to entry: The relationship between the pipe series, S, and the standard dimension ratio, SDR, is given 
by the following formula from ISO 4065  (see Bibliography [3]):  
 
 S =SDR −1
2 
 
3.1.14  
standard dimension ratio  
SDR  
numerical designation of a pipe series, which is a convenient round number, approximately equal to the 
dimension ratio of the nominal outside diameter, dn, and the nominal wall thickness, en 
 
3.1.15  
tolerance  
permitted variation of the specified value of a  quantity, expressed as the difference between the permitted 
maximum and the permitted minimum value  
 
3.1.16  
wall thickness tolerance  
ty 
permitted difference between the wall thickness at any point, e, and the nominal wall thickness, en 
 
Note 1 to entry : en ≤ e ≤ en + ty. 
 
3.2 Material terms  
 
3.2.1  
virgin material  
compound in the form of granules that has not been subjected to use or processing other than that required 
for its manufacture and to which no reprocessed or recycled materials have been added  
 
3.2.2  
own reprocessed material  
material prepared from clean, rejected and unused pipes, fittings, or valves, including trimmings from the 
production of pipes, fittings, or valves, that is reprocessed in a manufacturer's plant after having been 
previously p rocessed by the same manufacturer in the production of components by, for example, injection -
moulding or extrusion   
 
5 
  
3.2.3  
compound  
homogenous extruded mixture of base polymer (PE) and additives, i.e., anti-oxidants, pigments, carbon black, 
UV-stabilizers, at a dosage level necessary for the processing and use of components conforming to the 
requirements of this document  
 
3.2.4  
base polymer  
polymer produced by the material supplier for the manufacture of the comp ound according to this document  
 
3.2.5  
fusion compatibility  
ability of two similar or dissimilar polyethylene (PE) materials to be fused together to form a joint which 
conforms to the performance requirements of this document  
 
3.3 Terms related to material characteristics  
 
3.3.1  
lower confidence limit  of the predicted hydrostatic strength  
σLPL 
quantity, with the dimensions of stress, which represents the 97 .5 % lower confidence limit of the predicted 
hydrostatic strength at a temperature θ and time t 
 
Note 1 to entr y: It is expressed in Megapascals . 
 
3.3.2  
minimum required strength  
MRS  
value of σLPL at 20 °C and 50 years, rounded down to the next smaller value of the R10 series when σ LPL is 
below 10 MPa, or to the next lower value of the R20 series when σLPL is 10 MPa or greater  
 
Note 1 to entry : The R10 series conforms to ISO 3  and the R20 series conforms to ISO 497[4].  
 
3.3.3  
design coefficient  
C 
coefficient with a value greater than 1 which takes into consideration service conditions as well as properties 
of the components of a piping system other than those represented in the lower confidence limit  
 
3.3.4  
design stress  
σs 
allowable stress for a given application at 20 °C, that is derived from the MRS by dividing it by the design 
coefficient C, i.e.  
 
CMRS
s
 
 
Note 1 to entry : It is expressed in Megapascals.  
 
3.3.5  
melt mass -flow rate  
MFR  
value relating to the viscosity of the molten material at a specified temperature and load  
 
Note 1 to entry : It is expressed in grams per 10 min (g/10 min).  
 
 
 
 
  
 
6 
 3.4 Terms related to service conditions  
 
3.4.1  
nominal pressure  
PN 
numerical designation used for reference purposes related to the mechanical characteristics of the component 
of a piping system  
 
Note 1 to entry : For plastic piping systems conveying water, it corresponds to the allowable operating pressure (PFA) in bar, which can 
be sustained with water at 20 °C with a design basis of 50 years, and based on the minimum design coefficient:  
 
 
120
SDRCMRSPN  
 
Note 2 to entry : Research on long term performance prediction of PE water distribution systems shows a poss ible service life of at least 
100 years, see Bibliography [5] and [6].  
 
3.4.2  
allowable operating pressure  
PFA 
maximum hydrostatic pressure that a component is capable of withstanding continuously in service  
 
Note 1 to entry : See  Annex A.  
 
3.5 Terms related to joints  
 
3.5.1  
electrofusion joint  
joint between a PE socket or saddle electrofusion fitting and pipe or fitting with spigot ends, made by heating 
the electrofusion fittings by the Joule effect of the heating element incorporated at their jointin g surfaces, 
causing the material adjacent to them to melt and the pipe and fitting surfaces to fuse  
 
3.5.2  
butt fusion joint  
joint made by heating the planed ends of matching surfaces by holding them against a flat heating plate until 
the PE material reach es fusion temperature, quickly removing the heating plate and pushing the two softened 
ends against one another  
 
3.5.3  
mechanical joint  
joint made by assembling a PE pipe to another PE pipe, or any other element using a fitting that generally 
includes a co mpression part, to provide for pressure integrity, leaktightness and resistance to end loads  
 
3.5.4  
socket fusion joint  
joint made by heating the socket ends of matching surfaces by holding them against a flat heating plate until 
the PE material reaches fu sion temperature, quickly removing the heating plate and pushing the two softened 
ends against one another  
 
 
4 SYMBOLS AND ABBREVIATED TERMS  
 
4.1 Symbols  
 
For the purposes of this document, the following symbols apply.  
 
C design coefficient  
de outside diameter (at any point)  
dem mean outside diameter  
dem,max  maximum mean outside diameter   
 
7 
 dem,min  minimum mean outside diameter  
dn nominal outside diameter  
E wall thickness (at any point) of a fitting body  
e wall thickness (at any point) around the circumference of a component  
em mean wall thickness  
emax maximum wall thickness (at any point)  
emin minimum wall thickness (at any point)  
en nominal wall thickness  
ty wall thickness tolerance  
σs design stress  
σLPL lower confidence limit of the predicted hydrostatic strength  
 
4.2 Abbreviated terms  
 
For the purposes of this document, the following abbreviated terms apply.  
 
DN/OD  nominal size, outside diameter related  
LPL lower predicted limit  
MFR  melt mass -flow rate  
MRS  minimum required strength  
PE polyethylene  
PFA allowable operating pressure  
PN nominal pressure  
S pipe series  
SDR  standard dimension ratio  
 
 
5 MATERIAL  
 
5.1 Material of the component  
 
The material described in this document is a compound, which shall be supplied in the form of granules, 
suitable for the production of pipes complying with DMS 374 -2 or fittings complying with DMS 374 -3. 
 
NOTE  - Since PE 40 is not commonly used for pressur e applications, it is the intention of MBS/TC 2  to withdraw all references to this 
compound at the next revision of the DMS 374  series (all parts).  
 
5.2 Compound  
 
5.2.1  Additives and pigments  
 
The compound shall be made by the material producer by adding to the polyethylene base polymer only those 
additives and pigments ( e.g., carbon black) necessary for the manufacture of pipes and fittings conforming to 
DMS 374 -2 or DMS 374 -3, as applicable, and for their fusibility, storage, and use.  
 
All additives and pigments shall be uniformly dispersed.  
 
The carbon black used in the production of black compound shall have an average (primary) particle size of 
10 nm to 25 nm.  
 
 
  
 
8 
 5.2.2  Colour  
 
The colour of the compound shall be either black or blue.  
 
NOTE 1  - Compounds with other colours than black and blue are only intended for identification purposes, (stripes).  
 
Blue compound shall only be used for products in contact with water intended for human consumption.  
 
Yellow and orange compound is not allowed for p roducts according to the DMS 374 series (all parts).  
 
NOTE 2  - Yellow and orange colour are used for gas applications, in accordance with the ISO 4437  series (all parts).  
 
5.3 Physical characteristics of the compound  
 
5.3.1  Characteristics of the compound in the form of granules  
 
In the form of granules, the compound which is used for the manufacture of pipes and fittings shall have 
characteristics conforming to the requirements given in Table 1.  
 
 
Unless otherwise specified by the applicable test method, t he test pieces shall be conditioned at (23 ± 2) °C 
before testing in accordance with Table 1.  
 
Table 1 — Characteristics of PE compound in the form of granules  
 
1 2 3 4 5 
Characteristic   
 Requirementsa Test parameters  Test method  
Parameter  Value  
Compound density  ≥930 kg/m3 Test temperature  23 °C  ISO 1183 -1 or 
ISO 1183 -2 Number of test piecesb Shall conform to 
ISO 1183 -1 or 
ISO 1183 -2 
Carbon black  
contentc (2.0 to 2.5) % (by mass)  Shall conform to ISO 6964  ISO 6964  
Carbon black  
dispersionc  Grade ≤ 3  
Rating of dispersion A1, A2, 
A3, or B  Preparation of test 
piecesd Free 
 ISO 18553  
Number of test piecesb Shall conform to  
ISO 18553  
Pigment dispersione Grade ≤ 3  
Rating of dispersion A1, A2, 
A3, or B  Preparation of test  
piecesd Free ISO 18553  
 Number of test piecesb Shall conform to  
ISO 18553   
Volatile content  ≤350 mg/kg  Number of test piecesb 1 EN 12099  
Water contentf 
 
 ≤300 mg/kg  
(Equivalent to  
<0.03 % by mass)  Number of test piecesb 
 1 
 ISO 15512  
Oxidation  
induction time  
(Thermal stability)  ≥20 min  Test temperatureg 210 ISO 11357 -6 
Number of test piecesb 3 
Test atmosphere  Oxygen  
Melt mass -flow rate 
(MFR) for PE 40  0,20 ≤ MFR ≤ 1,40 g/10 minh 
Maximum deviation of ±20 % of 
the nominated value  Loading mass  2.16 kg  ISO 1133 -1 
Test temperature  190 °C  
Time  10 min  
Number of test piecesb Shall conform to  
ISO 1133 -1 
Melt mass -flow rate 
(MFR) for PE80 and 
PE 100  0.20 ≤ MFR ≤ 1,40 g/10 minh,i 
Maximum deviation of ±20 % of 
the nominated value  Loading mass  5 kg ISO 1133 -1 
Test temperature  190 °C  
Time  10 min  
Number of test piecesb 
 Shall conform to  
ISO 1133 -1  
 
9 
 a Conformity to these requirements shall be proved by the compound producer . 
 
b The number of test pieces given indicates the number required to establish a value for the characteristic described in Table 1. The 
number of test pieces required for factory production control and process control should be listed in the manufacturer’s qua lity plan. 
Guidance on assessment of conformity can be found in CEN/TS 12201 -7[2]. 
 
c Only for black compound . 
 
d In case of dispute, the test pieces shall be prepared by microtome method . 
 
e Only applicable for non -black compound . 
 
f Only applicable if the measured volatile content is not in conformity with its specified requirement. In case of dispute, the  requirement 
for water content shall apply. As an alternative method, ISO 760  may be used. The requirement applies to the compound producer at 
the stage of compound manufacturing and to the compound user at the stage of processing (if the water content exceeds the lim it, 
drying is required prior to use).  
 
g The test may be carried out at 200 °C or 220 °C provided that a clear correlat ion has been established. In case of dispute, the reference 
temperature shall be 210 °C.  
 
h Nominated value given by the compound manufacturer.  
p 
i Materials of nominated value 0 .15 ≤ MFR < 0 .20 can be introduced, in such case attention is drawn to the fusion compatibility (see 5.4). 
The lowest MFR value resulting from the maximum lower deviation of the nominated value should be not less than 0.15.  
 
5.3.2  Characteristics of the compound in the  form of pipe  
 
In the form of pipe, the compound which is used for the manufacture of pipes and fittings shall have 
characteristics conforming to the requirements given in Table 2.  
 
Unless otherwise specified by the applicable test method, the test pieces shall be conditioned at (23 ± 2) °C 
before testing in accordance with Table 2.  
 
NOTE  - Information on resistance to rapid crack propagation is given in Annex B.  
 
Table 2 — Characteristic of the PE compound in the form of pipe  
 
1 2 3 4 5 
Characteristic  
 Requirementsa Test parameters  Test method  
Tensile strength for  
butt-fusionb Test to failure:  
Ductile — Pass  
Brittle — Fail Pipe diameter  110 mm  ISO 13953  
Pipe diameter ratio  SDR 11  
Test temperature  23 °C  
Number of samplesc According to ISO 13953  
Resistance to slow  
crack growth  No failure during 
test period  Pipe diameter  110 mm  ISO 13479  
Pipe diameter ratio  SDR 11  
Test temperature  80 °C  
Internal test pressure  
for: 
PE 80  
PE 100   
 
8.0 bar  
9.2 bar  
Test period  500 h  
Type of test Water -in-water  
Number of samplesc According to ISO 13479  
Effect on water  
quality  According to existing national regulations  
Resistance to  
weatheringd  The weathered test 
pieces shall fulfil the 
requirements of the 
characteristics, a), 
b) and c) below:  Preconditioning:  
–Cumulative radiant  
exposuree 
–Number of  
samplesc ≥3.5 GJ/m2 
Shall conform to ISO 
16871  ISO 16871  
a) Decohesion of an 
electrofusion joint  ≤33,3 % brittle 
failure  Sample preparation  
dimension  
jointing  dn 110 mm / SDR 11  
ISO 11413 condition 1: 23 
°C ISO 13954  
b) Elongation at break  According to ISO 4427 -2:2019, Table 5  ISO 6259 -1 and  
ISO 6259 -3  
 
10 
 1 2 3 4 5 
Characteristic  
 Requirementsa Test parameters  Test method  
c)Hydrostatic 
strength (1 000 h at 
80 °C)  According to ISO 4427 -2:2019, Table 3  ISO 1167 -
1:2006f and 
ISO 1167 -2 
Resistance to rapid 
crack  propagationg,h,i Arrest  Pipe diameter  250 mm  ISO 13477  
Pipe diameter ratio  SDR 11  
Test temperature  0 °C 
Test medium  Air 
Internal test pressure  
for: 
PE 80  
PE 100   
 
8.0 bar  
10.0 bar  
Number of samplesc Shall conform to ISO 
13477  
OR 
 Arrest  Pipe diameter  500 mm  ISO 13478  
Pipe diameter ratio  SDR 11  
Test temperature  0 °C 
Test medium  Air 
Internal test pressure 
for: 
PE 80  
PE 100   
 
20.0 bar  
24.0 bar  
Number of samplesc Shall conform to ISO 
13478  
a Conformity to these requirements shall be proven by the compound manufacturer.  
 
b Preparation of samples in accordance with ISO 11414,  normal conditions at 23 °C.  
 
c The number of samples given indicates the quantity required to establish a value for the characteristic described in this tab le. The 
number of test pieces required for factory production control and process control should be listed in the manufacturer’s qu ality 
plan. Guidance on assessment of conformity can be found in CEN/TS 12201 -7[2]. 
 
d Only applicable for non -black compound.  
 
e For outdoor storage for 1 year to be valid globally, a cumulative radiant exposure of 7 GJ/m2 is required . 
 
f Measured dimensi ons according to clause 7.2 of ISO 1167 -1:2006  are applicable.  
 
g Applicable for compounds dedicated for pipes with wall thickness ≥32 mm.  
 
h If the requirements are met, the material is qualified for the full range of pipe produced in accordance with the scope of                        
DMS 374 -2. 
 
I If the requirements are not met for a given PE material, the critical pressure pc may be establi shed and used to determine the 
PFA for a material relative to diameter.  
 
PFA ≤ pc, where pc is determined in accordance with ISO 13478,  or 
 
PFA ≤ 3 .6 pc,S4 + 2 .6, where pc is determined in accordance with ISO 13477.  
 
 
5.4 Fusion compatibility  
 
5.4.1  The compounds conforming to Table 1 shall be fusible. This shall be demonstrated by the compound 
manufacturer for each compound of his own product range by checking that the requirement for the failure 
mode in a tensile test given in Table 2 is fulfilled f or a butt fusion joint prepared by using the parameters 
specified in ISO 11414:2009, Annex A  at an ambient temperature of (23 ± 2) °C from pipes both manufactured 
from that compound.  
 
For 0 .15 ≤ MFR < 0 .20 compounds, fusion compatibility of pipes with diam eter >200 mm and wall thickness 
>20 mm shall be investigated to confirm compatibility. If electrofusion is used, appropriate testing should be 
carried out to verify the fusion capability of such pipes.  
  
 
11 
 5.4.2  The compounds conforming to Table 1 are conside red fusible to each other. If requested, the compound 
manufacturer shall demonstrate this by checking that the requirement for the failure mode in a tensile test 
given in Table 2 is fulfilled for a butt fusion joint prepared by using the parameters as spec ified in                                      
ISO 11414:2009, Annex A  at an ambient temperature of (23 ± 2) °C from two pipes manufactured from the 
compounds from his own range covered by this request.  
 
NOTE  - This clause is not applicable to PE 40 materials. Pipes in these materials are joined using mechanical fittings.  
 
5.5 Classification and designation  
 
Compounds shall be designated by the type of PE material. The minimum required strength (MRS) shall 
conform to Table 3 when tested in the form of pipe.  
 
Table 3 — Classification and designation of compounds  
 
1 2 3 
Designation  
 Minimum required strength (MRS)  
MPa σs a 
MPa 
PE 100  10.0 8.0 
PE 80  8.0 6.3 
PE 40b 4.0 3.2 
a The design stress, σs, is derived from the MRS by application of the overall service (design) coefficient, C = 1.25.  
 
NOTE  - A higher value for C can be used; for example, if C = 1 .6, this gives a design stress of 5 .0 MPa for PE 80 materials. 
A higher value for C can also be obtained by choosing a higher PN class.  
 
b PE40 will be withdrawn from the next revision of the DMS 374 series.  
 
 
The compound shall be evaluated in accordance wit h ISO 9080 from pressure tests on pipes in accordance 
with ISO 1167 -1 and ISO 1167 -2 performed on pipes at least at three temperatures, where two of the 
temperatures are fixed to 20 °C and 80 °C and the third temperature is chosen between 30 °C and 70 °C, to 
find the σLPL. The MRS -value shall be derived from the σLPL and the compound shall be classified by the 
compound producer in accordance with ISO 12162.  
 
At 80 °C, there shall be no knee detected in the regression curve at t < 5 000 h.  
 
NOTE  - Testing has shown that for many compounds, no knee is detected before 1 year at 80 °C.  
 
The conformity of the designation of the compound to the classification given in Table 3 shall be demonstrated 
by the compound producer.  
 
Where fittings are manufact ured from the same compound as pipes, then the material classification is the 
same.  
 
For the classification of a compound intended only for the manufacture of fittings, test pieces in the form of 
extruded pipe made from the compound shall be used.  
 
 
6 EFFE CTS ON WATER QUALITY  
 
For compounds and components to be used in contact with water intended for human consumption, attention 
is drawn to potential restrictions on the use of products.  
  
 
12 
 Annex A  
(informative)  
 
Pressure reduction coefficient  
 
This annex is only given for the convenience of the reader. Whenever operating temperatures are higher than 
20 °C, reference should always be made to ISO 13761  (see Bibliography [ 8]). 
 
When a PE piping system is to be operated at a continuous constant temperature higher than 20 °C, a pressure 
reduction coefficient as given in Table A.1 may be applicable for PE 80 and PE 100. For reduction coefficients 
of PE 40, refer to ISO 13761[8]. 
 
Table A.1 — Pressure reduction coefficient for PE 80 and PE 100  
 
1 2 
Temperaturea,b 
°C Coefficien t 
20 1.00 
30 0.85 
40 0.73 
50 b 
NOTE  - If analysis according to ISO 9080 demonstrates that less reduction is applicable, higher factors and hence higher pressures 
may be applied.  
a For other temperatures between each step, interpolation is permitted (see also ISO 13761[8]).  
b For temperature s between 40 °C and 50 °C, see ISO 13761[7]  and consult the compound manufacturer.  
 
The continuous allowable operating pressure (PFA) is derived from the following formula:  
 
 PFA = fT × fA × PN  
 
where  
 
 fT is the coefficient according to Table A.1;  
 
fA is the derating factor related to the application (for the conveyance of water, the maximum  value of        
fA = 1); 
 
 PN is the nominal pressure.  
 
  
 
13 
 Annex B  
(informative)  
 
Resistance to rapid crack propagation  
B.1 General  
 
Rapid crack propagation (RCP) is the generation of a low ductility crack running at high speed (approximately 
300 m/s) along a pressurized pipeline. Propagation or arrest of the crack is dependent on the strain energy at 
the crack tip, which is influenced by the inter nal pressure of the fluid, which is in turn affected by the rate at 
which the fluid decompresses.  
 
If a fracture occurs in a water pipeline, the fluid is not subject to the same compression and energy release as 
that of a pipeline containing air or a gas. Therefore, propagation of a fast -running crack is much less likely to 
occur in a water pipe. Indeed, full -scale (FS) and S4 RCP tests on water pipes have shown that propagation 
does not occur when the pipe is completely filled (see Bibliography [ 9]). However, tests on large -diameter pipe 
containing both water and air at low temperature (<3 °C) have shown that the crack can propagate along the 
top of the pipe within the air pocket, but that higher pressures are required to sustain this propagation than 
those of air alone (see Bibliography [ 9] and [ 10]). The pressure to sustain propagation increases as the 
entrapped volume of air is decreased, hence minimizing the volume of entrapped air reduces the risk. Thus it 
is concluded that the risk of this phenome non occurring in a water pipe is extremely low and requires certain 
coincident conditions, i.e. initiation of a fast -running crack at the location of an air pocket in a large -diameter 
pipe operated at high pressure and in low -temperature conditions. Large diameter water supply pipelines are 
usually designed to eliminate any entrapped air, otherwise operational difficulties will be encountered.  
 
In the development of European standards for polyethylene water pipe, it has been concluded that RCP only 
needs to  be taken into account for pipe of wall thickness >32 mm. Testing has shown that most modern -day 
pipe compounds are resistant to RCP and have high resistance to slow crack growth, considerably reducing 
the risk of initiation.  
 
B.2 Initiation  
 
The initiatio n of RCP could be the result of impact damage, the growth of a crack through the wall or a crack 
developing from a poor fusion weld in certain coincident operating and environmental conditions.  
 
The phenomenon of RCP has been reported in pipelines of diffe rent materials, including steel and, in a few 
examples, plastics pipeline systems manufactured from older generation material.  
 
B.3 Parameters governing propagation/arrest  
 
The parameters that govern RCP if a crack is initiated are:  
 
a) internal pressure;  
 
b) pipeline temperature;  
 
c) rate of decompression of the conveyed fluid (see B.1); and 
 
d) fracture toughness of the pipe material.  
 
 
  
 
14 
 Bibliography  
[1] ISO 4437 -1, Plastics piping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 1: 
General  
[2] CEN/TS 12201 -7, Plastics piping systems for water supply, and for drainage and sewerage under 
pressure — Polyethylene (PE) — Part 7: Guidance for the assessment of conformity  
[3] ISO 4065, Thermoplastics pipes — Universal wall th ickness table  
[4] ISO 497:1973, Guide to the choice of series of preferred numbers and of series containing more 
rounded values of preferred numbers  
[5] Schulte U., Hessel J. Restlebensdauer von Kunststoffrohren nach einer Betriebszeit von 41 Jahren , 
3R in ternational (45), Heft 9/2006  
[6] Hoang E.M., Lowe D., (Exova UK) " Lifetime prediction of a blue PE100 water pipe. Polym. Degrad. 
Stabil . 2008 August, 93 (8) pp. 1496 –1503  
[7] ISO 11922 -1, Thermoplastics pipes for the conveyance of fluids — Dimensions and tolerances — Part 
1: Metric series  
[8] ISO 13761, Plastics pipes and fittings — Pressure reduction factors for polyethylene pipeline systems 
for use at temperatures above 20 degrees C  
[9] Greig M. Rapid crack propagation in hydrostatically pressurized poly ethylene pipe, Plastics and 
Rubber Institute Plastics Pipes VII Conference, September 1988  
[10] Greenshields, C.J., Fast brittle fracture of plastics pipes — Part 1: Water pressurised, plastics, rubber 
and composites processing and applications , 1997, Vol.  26, No. 9, p. 387  
[11] ISO 760, Determination of water — Karl Fischer method (General method)  
[12] ISO 18553, Method for the assessment of the degree of pigment or carbon black dispersion in 
polyolefin pipes, fittings and compounds  
  
 
  
  
 
 
ICS 93.025, 23.040.20, 23.040.45     DMS 374 -1:2021  
Second edition  
ISO 4427 -1:2019  
IDT 
 
 
 
 
 
 
 THE MALAWI BUREAU OF STANDARDS               CERTIFICATION MARK SCHEME  
The Malawi Bureau of Standards is the 
standardizing body in Malawi under the aegis 
of the Ministry of Industry and Trade.  Set up in 
1972 by the Malawi Bureau of Standards Act 
(Cap: 51:02), the Bureau is a parastatal body 
whose activities aim at formulatin g and 
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