Shurflow domestic water pump issues?

[Tim Good]

I have a Shureflo diaphragm pump from fresh water tank. It exits into a check valve then into an accumulator. The pump is a Shirflow 2088 rated at 15lpm (3.75gpm).

It was working fine but now seems to loose the ability to prime when the water tank reaches half full. Half way on the tank is just below the level that the pump installed at.

When the tank is full and the pump works here also seems to be air in the water system which suggests to me the pump is not sealed and either sucking in air from the pump or before it.

However I've check the pump and piping to it and all is secure and connections good. Also once pressurised the pump doesn't seem to leak so I'd doubt the pump has hole or leak somewhere. I've taken he pump to bits and all diaphragms seem fine.

I'm at a loss frankly as to what is up with it. Any suggestions?

 

[VicS]

I have a Shureflo diaphragm pump from fresh water tank. I
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I'm at a loss frankly as to what is up with it. Any suggestions?

I guess you have read the troubleshooting section of he manual , but I would double check for air in leaks into the pump suction plumbing. Also check / clean/ replace the valve assemblies in the pump.

Air in the water system would make the air in-leakage my 1st suspicion.

Why do you have a check valve on the pump discharge?

 

[Tim Good]

Air in the water system would make the air in-leakage my 1st suspicion.

Why do you have a check valve on the pump discharge?

Not sure. It was there before. Previous owner installed it. But I agree, the pump itself is an adjustable check valve.

I've changed and check the diaphragm and and everything is clean and smooth. Just can't see where air could get in. I might use my hot glue gun to seal the joints as a test. It'll come away easily afterwards.