The 2 gallon tank on my shallow well pump needs replacement, but?

Plumbing Forums

Help Support Plumbing Forums:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Qmavam

Member
Joined
Jul 18, 2023
Messages
20
Reaction score
9
Location
USA
I see there are 2 gallon expansion tanks and the there are 2 gallon tanks for pumps.
What is the difference?
 
Can I use an expansion tank as a storage tank on my pump?
Not effectively, there is a bladder with air that limits capacity to maybe 30-40 percent. If storage is needed a cistern or holding tank is best.
 
Maybe pay attention to what was replied to. I said nothing about expansion vs pressure tanks. It was regarding using an expansion tank for storage....
 
A 2-gallon tank on a pump is not a storage tank by any means. That size tank is solely to allow the pump switch to operate between the set pressures like 40 to 60 psi. I wouldn't even call a 20-gallon tank on a well pump a "storage tank". As GReynoldsd929 said, if you need storage, you need a cistern or holding tank.

And a better control system for well pumps is the Cycle Stop Valve instead of the standard on-off pressure switch. That system allows a smaller tank and provides a pretty much constant pressure to you house much like city water provides. It also increases the life of your well pump and saves energy to boot. Valveman on this forum is best to answer your question after you describe your wants and needs clear;y.
 
OK, the two gallon tank (with a bladder) I have used for the last 27 years, (I think this is the second one)
is on a pump used to water the garden and keep the greenhouse warm during a freeze. It's main purpose is to keep the pump from cycling.
So, as I see, it a water heater expansion tank is a tank with a bladder, A pre-charged tank for a pump is a tank with a bladder. I want to understand what is different and why I can't use the cheaper expansion tank on my pump.

PS
It was noticed that the pump was running but not pumping any water. I removed it, checked the impeller, it was fine, I tested the pump with a 5 gallon bucket of water, pumped fine, I tested the check valve on the well, it held water. I then noted I had emptied all the water out of the pre-charged tank, but it still held water, I pushed the Schrader valve and water came out. Then I removed the Schrader valve core and it was like I had a rocket in my hand. The bladder obviously has a hole in it, but I recharged it and put the pump system back together and it works for now. But I expect I'll need a new pre-charged tank before long.
Can someone explain how the tank being waterlogged would make the pump loose it's prime? I think that is the problem, but I don't know how it is..
 
I have not researched the differences between a small pressure tank and a expansion tank. I doubt there is much of a difference, maybe the diaphragm is attached differently on the pressure tank but I doubt it. If it was me I would try the expansion tank and see how it works.
 
A water heater expansion tank is to keep the pressure in the piping from increasing as the water slowly expands as it is heated. The diaphragm of a well pump pressure tank will flex significantly more than the diaphragm of a water heater expansion tank as the pressure increases rapidly when the pump turns on. The pressure in a well pump pressure tank will vary between 40 and 60 during normal operations, while the water heater expansion tank will basically operate within a few PSI of the set point.

I would say a water heater expansion tank will function fine for a well pump, but the life expectancy might be measured in days or weeks, not years.
 
Back
Top