 
 
   
  
 
 
 
 
 
 
 
 
  
 
 ICS 93.025, 23.040.20, 23.040.45     DMS 374 -5:2021  
First edition  
ISO 4427 -5:2019  
IDT 
 
 
 
DRAFT MALAWI STANDARD  
 
 
 
 
 
 
 
 
 
 
 
 
Plastics piping systems — 
Polyethylene (PE) pipes and fitt ings for 
water supply —  
Part 5: Fitness for purpose of the 
system  
 
 
 
 
 
 
 
 
 
 
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 -5:2021  
Second edition  
ISO 4427 -5:2019  
IDT 
 
 
 
 
 
 
Plastics piping systems — Polyethylene 
(PE) pipes and fittings for water supply —  
Part 5: Fitness for purpose of the system  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 8 pages  
© Copyright reserved   
 
  
  
i 
 TABLE OF CONTENTS  
 
Contents  ................................ ................................ ................................ ................................ ...................  Page  
Foreword  ................................ ................................ ................................ ................................ ....................   i 
Introduction  ................................ ................................ ................................ ................................ ................   i 
Scope  ................................ ................................ ................................ ................................ .........................   1 
Normative references  ................................ ................................ ................................ ................................   1 
Terms, definitions, symbols and abbreviated terms  ................................ ................................ ..................   2 
Fitness for purpose of pipes and/or fittings assemblies  ................................ ................................ ............   2 
Bibliography  ................................ ................................ ................................ ................................ ...............   8 
 
 
FOREWORD  
 
This Draft Malawi Standard  is adopted from the international standard, ISO 4427 -5: 2019  Plastics piping 
systems — Polyethylene (PE) pipes and fittings for water supply — Part 5: Fitness for purpose of the system . 
 
Acknowledgement is made for the use of t he above standard.  
 
 
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;  
Ruo Consultants; and  
Southern Region Water Board  
 
 
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 consumpti on, 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 th e 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  . 
 
 
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 374-5:2021 
DRAFT MALAWI STANDARD  
Plastics piping systems — Polyethylene (PE) pipes and 
fittings for water supply —  
Part 5: Fitness for purpose of the system  
 
 
1 SCOPE  
 
This document specifies the characteristics of the fitness for purpose of pipes and/or fittings assemblies 
made from polyethylene (PE) for buried or above ground application s, intended 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.  
 
NOTE 1  - The intended uses include sea outfalls, laid in water and pipes  suspended below bridges.  
 
NOTE 2  - This document is intended to be only used by the product manufacturer to assess the performance of components according 
to DMS 374 ‑2 and/or DMS 374 ‑3 when joined together under normal and extreme conditions. It is not in tended for on -site testing of pipe 
systems.  
 
This document also specifies the test parameters for the test methods referred to in this document.  
 
In conjunction with the other parts of the DMS 374  series, this document is applicable to PE pipes, fittings, 
their joints and to joints with components 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 t emperature.  
 
NOTE 3  - For other operating temperatures, guidance is given in DMS 374 ‑1: 2021, Annex A.  
 
The DMS 374  series covers a range of maximum allowable operating pressures and gives requirements 
concerning colours.  
 
 
2 NORMATIVE REFERENCES  
 
The fol lowing standards contain provisions which, through reference in this text, constitute provisions of this 
standard. All standards are subject to revision and, since any reference to a standard is deemed to be a 
reference to the latest edition of that standa rd, parties to agreements based on this 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 standards can be obtained from  the Malaw i Bureau of Standards . 
 
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 1167 -4, Thermoplastics pipes, fittings and assemblies for the conveyance of fluids — Determination of 
the resistance to inte rnal pressure — Part 4: Preparation of assemblies ; 
 
ISO 4427 -1:2019 , Plastics piping systems for water supply, and for drainage and sewerage under pressure 
— Polyethylene (PE) — Part1: General ;  
 
ISO 4427 -3:2019, Plastics piping systems for water supply, a nd for drainage and sewerage under pressure 
— Polyethylene (PE) — Part 3: Fittings . 
                                                 
1 1 bar = 0 .1 MPa = 105 Pa; 1 MPa = 1 N/mm2.  
2 
  
ISO 11413:2019 , Plastics pipes and fittings — Preparation of test piece assemblies between a polyethylene 
(PE) pipe and an electrofusion fitting ; 
 
ISO 11414:2009 , Plastics  pipes and fittings — Preparation of polyethylene (PE) pipe/pipe or pipe/fitting test 
piece assemblies by butt fusion ; 
 
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 13955 , Plastics pipes and fittings — Crushing decohesion test for polyet hylene (PE) electrofusion 
assemblies ; 
 
ISO 13956 , Plastics pipes and fittings — Decohesion test of polyethylene (PE) saddle fusion joints — 
Evaluation of ductility of fusion joint interface by tear test ; and 
 
ISO 17885 , Plastics piping systems — Mechanical  fittings for pressure piping systems — Specifications . 
 
 
3 DEFINITIONS  
 
For the purposes of this document, the terms, definitions, symbols and abbreviated terms given in                    
DMS 374 -1 apply.  
 
 
4 FITNESS FOR PURPOSE OF PIPES AND/OR FITTINGS ASSEMBLIES  
 
4.1 Method of preparation of assemblies for testing  
 
4.1.1  General  
 
The assemblies shall be made by using pipes conforming to DMS 374 -2 and fittings conforming to                     
DMS 374 -3. 
 
Test pieces for pressure testing shall be closed with pressure -tight, end -load-bearing end caps, plugs, or 
flanges which shall be provided with connections for the entry of water and release of air.  
 
The peelable layer of peelable -layer pipe shall be removed in the area of the joint prior to jointing.  
 
If failures that call for a redesign of the fitting are detected during testing according to this document, 
retesting according to DMS 374 -3 automatically becomes necessary.  
 
4.1.2  Grouping  
 
For testing purposes, the size groups for pipes and fittings shall  be in accordance with Table 1.  
 
Table 1 — Size groups for pipes and fittings  
 
1 2 3 4 5 6 
Size group  
 1 2 3 4 5 
Nominal outside diameter,  
dn ≥16 and <75  ≥75 and <250  ≥250 and <710  ≥710 and 
<1 800  ≥1 800  
 
 
One diameter from each size group (see Table 1) per product type (see 4.1.3.) shall be taken as test pieces.  
 
4.1.3  Fitting types  
 
For testing purposes, assemblies shall be classified as foll ows:  
3 
  
— (A) electrofusion socket joints;  
 
— (B) electrofusion saddle joints;  
 
— (C) butt fusion joints;  
 
— (D) mechanical joints;  
 
— (E) socket fusion joint.  
 
4.1.4  Electrofusion joints (A and B)  
 
PE pipes and fittings intended to be used for jointing by e lectrofusion shall be prepared and assembled in 
accordance with ISO 11413.  The conditions for the preparation of the joints are given in  4.2.2.1  for the 
assessment of fitness for purpose of the system under normal conditions and in 4.2.2.2  for the assessme nt 
of fitness for purpose of the system under extreme conditions.  
 
For joints with electrofusion saddle fittings, the electrofusion saddle fitting shall be fused to the pipe while it is 
pressurized to the allowable maximum operating pressure. The pipe shal l be cut immediately after the 
manufacturer's prescribed cooling time has elapsed.  
 
For straight equal electrofusion socket fittings (couplers), test joints on selected diameters out of the product 
range shall be prepared with a gap of 0 .05 dn between the pipe end and the maximum theoretical depth of 
penetration of the fitting, where for diameters greater than 225 mm, the adjoining pipes shall be arranged to 
provide the maximum angular deflection possible for the fitting, limited to 1 .5°. 
 
4.1.5  Butt fusion  joints (C ) 
 
PE pipes and spigot end fittings intended to be used for jointing by butt fusion shall be prepared and 
assembled in accordance with ISO 11414.  The conditions for the preparation of the joints are given in 4.2.3.1  
for the assessment of fitness for purpose of the system under normal conditions and in 4.2.3.2  for the 
assessment of fitness for purpose of the system under extreme conditions.  
 
4.1.6  Mechanical joints (D)  
 
For mechanical joints, the assembly of the PE pipe and the fitting shall be pre pared in accordance with               
ISO 17885.  
 
4.1.7  Socket fusion joints (E)  
 
Socket fusion joints shall be prepared as recommended by the manufacturer.  
 
4.2 Requirements for fitness for purpose of the assemblies  
 
4.2.1  General  
 
When tested in accordan ce with the test methods in Table 6 using the indicated parameters, joints prepared 
in  accordance  with 4.1 shall have mechanical characteristics conforming to the requirements given in Table 
6, as applicable.  
 
4.2.2  Fitness for purpose of the electrofusio n assemblies (A and B)  
 
4.2.2.1  Under normal conditions (ambient temperature 23 °C)  
 
For the assessment of fitness for purpose of the system under normal conditions, electrofusion joints shall 
have the characteristic of decohesive resistance or cohesive st rength, as applicable, conforming to the 
requirement given in Table 6, using the assembly condition 1 as specified in Annex C of ISO 11413  at an 
ambient temperature of 23 °C ± 2 °C and the scheme listed in Table 2.  
 
 
 
  
4 
 Table 2 — Scheme for electrofused ass emblies  
 
1 2 3 
Electrofusion fitting  Pipe  
PE80a 
SDR maximumb PE 100  
SDR minimumb 
PE 80  X X 
PE 100  X X 
a If PE80 pipes with SDR maximum are not available, PE100 pipes with SDR maximum may be used.  
b Pipe SDR maximum and pipe SDR minimum as declared by  the fitting manufacturer.  
 
The fitting manufacturer shall declare the pipes ( e.g., SDR range, material designation) to which the fittings 
can be fused and the applicable fusion procedures and parameters (e.g. times, temperatures). If there is a 
need for deviation in fusion procedures, the fitting manufacturer shall state this clearly.  
 
4.2.2.2  Under extreme conditions  
 
For electrofusion joints, the characteristics to be examined for fitness for purpose of the fittings under 
extreme conditions shall confor m to Table 3.  
 
When tested in accordance with the test methods as specified in Table 6 using the indicated parameters, the 
joints shall have characteristics conforming to the requirements given in Table 6.  
 
Table 3 — Relationship between joints and charact eristics  
 
1 2 3 
Electrofusion socket joint  
including socket fittinga 
(A) Electrofusion joint including  
saddle fittinga 
(B) Associated characteristics  
Pipe: MRS maximumb 
SDR minimumb 
Joint: conditions 2.2 and 3.2c  Decohesive resistance  
 Pipe: MRS maximu mb 
SDR minimumb 
Joint: conditions 2.2 and 3.2c Evaluation of ductility of fusion joint 
interface  
a If accepted by the end -user, the minimum and maximum energy conditions 2.2 and 3.2 can be replaced by a nominal energy at a 
given ambient temperature Ta defined by the fitting manufacturer (see ISO 11413, 4.3 ). 
b As declared by the fitting manufacturer according to 4.2.2.1.  
c As specified in Annex C of ISO 11413  with Tmin and Tmax as stated in the fitting manufacturer’s technical specification.  
 
The fitting manufacturer shall declare according to Table 3, column(s) A or B, as applicable, the fitness for 
purpose of the assembly under extreme conditions with the type of pipe being specified.  
 
4.2.3  Fitness for purpose of butt fusion assemblies (C)  
 
4.2.3.1  Unde r normal conditions (ambient temperature 23 °C)  
 
For the assessment of fitness for purpose of butt fusion assemblies under normal conditions, butt fusion 
joints shall have the characteristic of tensile strength conforming to the requirement given in Table 6, using 
the parameters as specified in ISO 1141 4, Annex B,  condition 1 at an ambient temperature of 23 °C ± 2 °C 
and the scheme listed in Table 4.  
 
 
 
 
 
 
  
5 
 Table 4 — Scheme for butt -fused joints  
 
1 2 3 
Pipe/spigot end fitting  Pipe  
PE 80  PE 100  
 X Xa 
 Xa X 
a Only when requested by the purchaser . 
 
NOTE  - Table 4 is to be interpreted as follows: as an example, for a pipe or a spigot end fitting made from a PE 80 compound, the jo int 
is tested with a pipe made from PE 80 compound. When requested by the pur chaser, for mixed compound joints, test pieces are used 
incorporating PE 80 and PE 100 compounds.  
 
If pipes according to DMS 374 -2 are produced from different compounds, the pipe manufacturer shall 
declare, according to 4.2.3.1, which pipes are compatible for butt fusion.  
 
The fitting manufacturer shall declare, according to 4.2.3.1,  the standard dimension ratio (SDR) range and 
MRS values of pipes to which the manufacturer's fittings can be fused and the applicable fusion procedures 
and parameters ( e.g., times, temperatures). If there is a need for deviation in fusion procedures, the fitting 
manufacturer shall state this clearly.  
 
4.2.3.2  Under extreme conditions  
 
For butt fusion joints, the characteristics to be examined for fitness for purpose of the syste m under extreme 
conditions shall conform to Table 5.  
 
Table 5 — Relationship between joints and fitness for purpose of the system characteristics  
 
1 2 
Butt fusion joint  
(C) Associated characteristics  
Both components of the joint: same MRS and same SDR  
Joint: minimum and maximum conditiona Hydrostatic strength  
(80 °C, 165 h)  
Tensile strength for butt fusion joint  
a As specified in ISO 11414, Clause 7,  item a) concerning misalignment and the limit values of fusion parameters 
conforming ISO 11414, Annex B , conditions 2 and 3.  
 
When tested in accordance with the test methods as specified in Table 6 using the indicated parameters, the 
joints shall have characteristics conforming to the requirements given in Table 6 . 
 
The fitting manufacturer shall declare according to Table 5 , as applicable, the fitness for purpose of butt 
fusion welds under extreme conditions.  
 
The pipe manufacturer shall declare according to Table 5 the fitness for purpose of butt fusion welds 
produced from PE pipes, PE pipes with co -extruded layers, or PE pipes with peelable layers under extreme 
conditions.  
 
4.2.4  Fitness for purpose of the mechanical assemblies (D)  
 
Mechanical assemblies shall conform to ISO 17885,  with fitness for purpose to be agreed between the  
manufacturer and the customer.  
 
4.2.5  Fitness for purpose of socket fusion assemblies (E)  
 
Fitness for purpose of the socket fusion assemblies shall be agre ed between the manufacturer and the 
customer.  
 
 
 
 
  
6 
 4.3 Conditioning  
 
The test pieces shall be conditioned at 23 °C ± 2 °C before testing, unless otherwise specified by the 
applicable test method as specified in Table 6 . 
 
4.4 Requirements  
 
The requirements for characteristics of fitness for purpose of the system are given in Table 6 . 
 
Table 6 — Characteristics for fitness for purpose of assemblies  
 
1 2                      3                    4           6 
Characteristic  Requirements  Test parameters  Test method  
Parameter  Value  
Hydrostatic  
strength  
(80 °C, 165 h)  
(C) No failure during 
the test period a End caps  ISO 1167 -1:2006  
Type A  ISO 1167 -1:2006  
together  with 
ISO 1167-2, or 
ISO 1167 -4, as 
applicable  Orientation  Free 
Conditioning time  Shall conform to ISO 
1167 -1:2006  
Number of test pieces b 3 
Type of test c Water -in-water  
Circumferential 
(hoop) stress in 
piped for: PE 80  4.5 MPa  
PE 100  5.4 MPa  
Test period  165 h  
Test temperature  80 °C  
Decohesive 
resistance 
(A) Length of 
initiation 
rupture ≤ L/3 
in brittle failure e Test temperature  23 °C  ISO 13954  
Number of test pieces b Shall conform to ISO 
13954  
Test temperature  23 °C  ISO 13955  
Number of test pieces b,f Shall conform to ISO 
13955  
Evaluation of 
ductility of fusion 
joint in terface d,g 
(B) Ld ≤ 50 % and  
Ad ≤ 25 %, brittle  
failure  Test temperature  23 °C  ISO 13956  
Number of test pieces b Shall conform to ISO 
13956  
Tensile strength for 
butt fusion h (C) Test to failure: 
ductile: pass  
brittle: fail  Test temperature  23 °C  ISO 13 953 
Number of test pieces b Shall conform to ISO 
13953  
a Only brittle  failures  shall  be taken  into account.  If a ductile  failure  occurs  before  165 h, the test is permitted  to be repeated 
according to 4.5. 
b The number of test pieces given indicates the number required to establish a value for the characteristic described in Table 5 . 
The number of test pieces required for factory production control and process control should be listed in the m anufacturer’s  
quality  plan.  Guidance  on assessment  of conformity  can be found  in Reference  [2] in the Bibliography.  
c Alternatively,  for dn > 450 mm, the test can also be performed  water  in air. In case  of dispute,  water -in-water shall be used.  
d The test pressure shall be calculated using the design standard dimension ratio (SDR) of the fitting.  
e Longest  length  of brittle  failure  in any of the test samples,  with L being  the nominal  length  of the fusion  zone  of the 
electrofus ion socket fitting.  
f Test sample  can be mechanically  reduced  in wall thickness  for testing  purpose  of large  diameter  fittings  by keeping  a minimum 
of 15 mm wall thickness of each component.  
g Alternatively, for fittings type (B) dn > 450 mm, this characte ristic can be checked by the strip -bend test according to ISO 21751  
(see Reference [ 3] in the Bibliography.)  
h Applicable to dn 90 mm and above.  
 
  
7 
 4.5 Retest in case of failure at 80 °C  
 
A fracture in a brittle mode in less than 165 h shall constitute a failure; however, if a sample in the 165 h test 
fails in a ductile mode in less than 165 h, a retest shall be performed at a selected lower stress in order to 
achieve the minimum required time for the selected stress obtained from the line through the recommended 
stress/time points given in Table 7  
 
Table 7 — Circumferential (hoop) stress at 80 °C and associated minimum test period  
 
1 2 3 4 5 6 
PE40  PE 80  PE100  
Stress  Minimum test 
time Stress  Minimum test 
time Stress  Minimum test 
time 
MPa h MPa h MPa h 
2.5 165 4.5 165 5.4 165 
2.4 230 4.4 233 5.3 265 
2.3 323 4.3 331 5.2 399 
2.2 463 4.2 474 5.1 629 
2.1 675 4.1 685 5.0 1 000  
2.0 1 000  4.0 1 000  — — 
 
  
8 
 Bibliography  
 
[1] ISO 4437 -5, Plastics p iping systems for the supply of gaseous fuels — Polyethylene (PE) — Part 5: 
Fitness for purpose of the system  
 
[2] CEN/TS 12201 -7, Plastics piping systems for water supply — Polyethylene (PE) — Part 7: Guidance for 
the assessment of conformity  
 
[3] ISO 217 51, Plastics pipes and fittings — Decohesion test of electrofusion assemblies — Strip-bend test  
  
 
  
  
 
 
ICS 93.025, 23.040.20, 23.040.45     DMS 374 -5:2021  
First  edition  
ISO 4427 -5:2019  
IDT 
 
 
 
 
 
 
 THE MALAWI BUREAU OF STANDARDS               CERTIFICATION MA RK 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 activi ties aim at formulating and 
promoting the general adoption of standards 
relating to structures, commodities, materials, 
practices, operations and from time to time 
revise, alter and amend the same to 
incorporate advanced technology.  To bring the advantages  of standardization 
within the reach of the common consumer, the 
Bureau operates a Certification Mark Scheme. 
Under this scheme, manufacturers who 
produce goods that conform to national 
standards are granted permits to use the 
Bureau’s “Mark of Quality” de picted below on 
their products.  This Mark gives confidence to 
the consumer of the commodity’s reliability.  
 
 
 
 
 
 