SINGLE DIAPHRAGM PRESSURE TANK - PTB 450

Diaphragm tanks are commonly used on 
the discharge manifold to provide water 
storage for the system in very low flow situations.
 It decreases the running time of the booster pumps,
 thereby making the system more energy effective.
An advantage of bladder pressure tanks is that
 they typically last longer than diaphragm pressure tanks,
 since they don't have a diaphragm that can fail.

Diaphragm pressure tanks are the most 
efficient type of pressure tank and require the 
least amount of maintenance due to the use of 
a rubber lining inside that separates the air and the water.
 This rubber lining acts as the bladder would,
 but its connection is permanent to the tank. 

Therefore, it is not replaceable.
If this happens, there is little air l
eft in the tank to become compressed,
 so the pump runs nearly every time water is used.
 In addition, too much air in the tank is a problem
 because it reduces the space for water storage.
 Extra air must be released or the tank will become air-bound.