Pump only fully Primes when Sand Filter is put in backwash and will slowly lose prime when in filter mode

[m1k_3]

I have been having ongoing issues with my pump staying primed. I thought it might be on the suction side but I think I have proven that is not the case. I can fully prime the pump when the Sand filter is put in backwash. Once primed if I move the filter back to filter mode my pump will lose prime and eventually shut off because of no flow.

I also have a waterfall and tried priming when I had the waterfall on instead of the return jets and it does not fully prime. So this most likely rules out the return lines as the problem. Unless return lines to water fall and jets have issues. So now I am thinking this is my heat pump or sand filter that is at fault.

I am thinking I will go to the local supply store and get some plumbing supplies so I can bypass the sand filter and heat pump to isolate further.

Does anyone have any other thoughts?

 

[1Sammy]

If you lose prime the problem is between the pool and the input to your pump basket. By passing the filter gives you more pressure so you have more lift to get the water to the basket.

 

[m1k_3]

I haven't bypassed my filer yet. I was thinking of doing that to isolate the problem. My pump will not fully prime if my filter is in filter mode or recirculate mode. The only way I can get the pump to fully prime is if I put my sand filter in backwash mode.

If I fully prime my pump in backwash mode and switch the filter back to filter mode I slowly lose prime.

 

[michael_bluth]

i have been all over the place with my pump and i notice a similar thing. I was able to prime the pump earlier this season, but have had no luck the passed couple weeks. I have a check valve after my pump, before the filter and sometimes it is barely open. what purpose does it serve? basically to monitor output of the pump? do i need to replace the pump - it's over 10 years old. would a small leak around the waist of the filter housing contribute to the problem?

 

[m1k_3]

Maybe something simple like your o-ring on the filter basket lid?

 

[michael_bluth]

i also have the in-ground floor cleaning, so i replaced the leaf-vac o-ring, union o-ring just before pump, and lid seal. no air bubbles going into to leaf-vac, so if a suction side leak, can only assume it is somewhere just before pump, or pump itself.