20 Chapter 1 Introduction to Statistical Quality Control, 5th Edition by Douglas C. Montgomery. 39Copyright (c) 2005 John Wiley & Sons, Inc.Chapter 1 Introduction to Statistical Quality Control, 5th Edition by Douglas C. Montgomery. 40Copyright (c) 2005 John Wiley & Sons, Inc.
Water hardness is a measure of the dissolved mineral content of water. There are two types: the general hardness (GH) and carbonate hardness (KH). When keeping freshwater fish and plants, the GH and the KH of aquarium water should match their natural habitat.
NPSHA is a measure that corresponds to the level of pressure at the pump suction. The higher the pressure, the higher the NPSHA and the better the pump will operate. Normally we measure pressure with a gauge that is calibrated in psig (pound per square inch gauge) or kPa in the metric system.