Pressure tank filling

[Eknight]

Dumb question #582! I’m reinstalling the pressure tank on our irrigation well cause the idiot construction guy missed the dumpster and knocked the tank right off the mounting block breaking the fitting. The bladder is good and the air pressure is fine, but of course the tank is empty of water. After reinstalling how does the water get back into the tank without bleeding the air that’s now in the water half of the tank below the diaphragm? That air has to go somewhere before it can fill with water right.

 

[LLigetfa]

A properly inflated diaphragm would be pressing up against the bottom of the tank when there is no water pressure so there should not be any air on the water side.

 

[Sponsor]

 

[Valveman]

The air doesn't go anywhere, it is compressed to act like a spring. The compressed air pushes on the diaphragm which in turn pushes water out of the tank.

 

[Bannerman]

As LL said, the pre-charge air pressure within the tank's air chamber, will deflect the diaphragm so it will push against the bottom of the water chamber whenever the tank contains 0 water, so there will be little or no air within the water chamber.

Once the pump is activated, water pressure from the pump will pushback on the diaphragm, so when the water pressure exceeds the tank's air precharge pressure, water will then begin to enter the tank's water chamber. As water pressure from the pump continues to rise, additional water entering the tank will further deflect the diaphragm backward toward the air chamber, thereby causing the air pressure within the air chamber to rise as it is being further compressed, equal to the pressure of the incoming water.