Check valve on Suction side of Pump

[PlumblessInSeattle]

Qty 2 300 gallon water storage tanks serving the suction side of an above ground Jet pump. There is a check valve between the suction side of the pump and the storage tanks. I don't think the check valve should be there. The stored water is above the suction inlet side of the pump. Do you think the check valve in the attached photo is correct? If Yes, ease let us know why.

 

[Reach4]

I think there needs to be a check valve between the pressure tank and the storage tanks. I am not sure if it could be on the output side of the pump. I would think so.

 

[Sponsor]

 

[LLigetfa]

I don't think the check valve should be there.

That is not unlike most any shallow or deep well jet pump installation having a footvalve on the intake.

Why do you think it should not be there?

 

[LLigetfa]

I am not sure if it could be on the output side of the pump. I would think so.

Why?

 

[Bannerman]

While the back pressure from the pressure tank will be stronger than the weight of the water above the check valve to ensure the check valve will fully close while the pump is not running, the check valve located directly at the inlet to the pump is likely to cause a cavitation situation within the pump.

The prescribed minimum length for a straight length of pipe before the pump inlet is 10X the diameter of the supply pipe so any item that will cause flow disturbance or turbulence such as an elbow, reducer, tee, valve etc will need to be located at a greater distance from the pump.

 

[LLigetfa]

While the back pressure from the pressure tank will be stronger than the weight of the water above the check valve to ensure the check valve will fully close while the pump is not running, the check valve located directly at the inlet to the pump is likely to cause a cavitation situation within the pump.

You are selling FUD. All jet pumps with a foot valve see the back pressure from the pressure tank plus the additional weight of the water column at .43 PSI per foot.

As for turbulence causing cavitation, that too is FUD. It may have some credence if drawing from max depth, but with the storage tanks providing positive head, it is a non-issue.

 

[Valveman]

While you should always have some straight pipe before the inlet of the pump, the check valve on the suction won't hurt anything on a small pump like that. The only problem I see is that there is no Cycle Stop Valve on the discharge of the pump and you wasted a lot of money on way too large a pressure tank.