An important thing to remember,
the higher the operating pressure –
the larger the tank must be.
Pressure and tank size have a direct correlation
– as one increases, so does the other.
Most residential pressure tanks come in
5 sizes. Roughly, 20, 30, 50, 60 and 80 gallons.
What most people don't realize is that pressure
tanks don't hold that much water.
A general guideline is that 1/3 of the tank holds water and the rest.
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.