Low Suction & no tank pressure

[mreidnz]

I have been having trouble recently with poor suction and the filter tank is not pressurizing.

Symptoms:
1-low suction. Not enough to drive pool cleaner (I have a Zodiac MX6 In-Ground Suction Side Pool Cleaner)
2- Triton 2 sand filter not pressurizing. Pressure gauge less than 5 psi
3- No apparent air in the strainer housing[/list][/list]

Here are all of the things I have done recently.
1- replaced all O-rings/seals on the pump and housing
2- replaced the "Push-Pull" backwash valve for a side mount multiport valve
3- used a hose and back washed the suction side pipes to make sure there was no blockage
4- replaced the pool vacuum hose
5- replaced the tank pressure gauge
6- replaced the pump impeller
7- emptied old sand and cleaned inside of filter tank and replaced with filter balls

Everything was working well and the water was about the best it has ever been, but about two weeks later it seemed to lose suction.

If I backwash, the flow is powerful and this seems to get the pool cleaner moving nicely. However, the cleaner stops again after about 15-30 minutes.

Any assistance or advice will be much appreciated. Thanks in advance

[Teapot1]

Still sounds like a basic vacuum side air leak and you loose prime after a few minutes.
Shame you swapped a slide valve for a multiport because multiports are poor regarding flow and increase the resistance of the circuit lowering the flow. Pollyballs, more plastics in the environment we dont need. The best filtration media is Dr Drydens activate AFM ng, eco friendly, recycled glass that can be recycled again, never needs changing, filters finer than any other media and reduces costs.

[Denniswiseman]

Your filter may be clogging up as it works well after a backwash
Let's have your numbers (CYA is very important) Use a pool store if you don't have a FAS/DPD kit
FC:
TC:
pH:
TA:
CH:
CYA:

[Teapot1]

Clogged filter, I would expect to see the new pressure gauge rising above 5psi.