Pressure Tank sizing

Need some advice on pressure tanks, please. Currently undergoing conversion from community water system to private well; contactor intalling submersible jet pumps and fiberglass pressure tanks. Previous house lived in had shallow jet pump and 20g fiberglass tank (Schrader valve on top) and with this system the pump would kick on everytime you flushed the toilet; cut-in/off were always w/i specs. My conclusion was that tank size inadequate. Contractor for new system also installing 20g tanks, but says will be more than adequate for family of 5 because new tanks entirely filled with air, i.e., there is no bladder. I have my doubts and would appreciate any thoughts on the matter. I could mention brandnames of equipment and models installed, but didn't want to break any Forum rules. Thanks. Bill

 

The rule of thumb on sizing pressure tanks is this:
One gallon of drawdown for each gallon of pump capacity. In other words, if the pump supplies 15 gpm, the tank should be big enough to have 15 gallons of drawdown.
I would guess that a 20 gallon, non bladder type tank is way too small!!
BTW, I think you must have meant submersible well pump, not submersible jet pumps.

 

Hi Bren,
-I completely agree with Pumpman's opinion. I feel for a family of 5 you need at least a 38-40 gal tank. (sounds like somebody's trying to trim costs ).
Post back and let us know what happens.

 

Thanks a lot for the good advice, people. Well driller is down 520' and still no water, so maybe this will give me some time to make my case (with your advice) for a larger pressure tank. Will let you know what comes out in the wash. -- Bill

p.s., sorry about using the wrong terminology for the submersible pump.

 

You can't go too large in my opinion. The pump run will longer but less often with a larger tank. You can go too small. The pump will cycle too often.

Get the largest one you can fit in the space and afford.