Backwash/Rinse/Prime issue

[Hdreaver]

Hello All!

Hoping someone might be able to help - I’ve recently bought a home with an old fibreglass pool (35,000ltrs).

Sometimes when I turn the pump on it turns on and runs no problems, other times it doesn’t - I can’t seem to find a consistent issue. It seems though that often when the filter is running, if I then turn to backwash/rinse it will lose prime on one of those settings and there seems to be a lot of air that comes back into the pool pump basket lid. I can’t leave it on timer as it doesn’t always turn on and work properly. Water level is also high and not an issue and have dug up pipe work from skimmer to pump, no leaks.

I have checked for a suction side air leak, had someone out who diagnosed leak in skimmer box (repaired small crack & replaced gasket connection, re-sealed other PVC joins). When filter turns on it primes without air and no change when using Kreepy Krawley - except if there is some air in the line but this comes out quickly.

I thought that maybe the sand was either old or there was a broken lateral so I have removed sand and checked laterals. They all look in okay condition and I will replace the sand but it doesn’t look really dirty. Also, multi port gasket etc. looks okay. Pool King fibreglass pool filter - unsure what make the pump is.

Any thoughts on what I might be missing from anyone? I haven’t taken the pump apart but I have checked the impeller which doesn’t seem to be blocked.

I will happily update everyone on what the issue is once I work it out.

Thanks so much!