Pump suction keeps going away

[gmlear]

Last year I bought a house with an old inground pool that uses a Hayward Super Pump and a Hayward 270T sand filter.

This year, after changing the sand (350 lbs.), I've encountered a problem. When I go to suction the bottom of the pool, the suction on the pump decreases significantly, until there is no water flow whatsoever--there is water in the pump system (because the basket section is full to the lid with water), it's just not moving. After that, I have to switch the pump off and on a couple of times, which starts the water moving again.

It appears to me that the problem is with the pump not having enough strength, so that when it's tasked with suction duties, it slows down to a halt. (Note that the motor is still running). Do I need to replace the impeller? Seals? Can anyone make a recommendation?

Thanks.

 

[Melt In The Sun]

Welcome to TFP!
I don't do a whole lot (any) of manual vacuuming, but what you're describing sounds strange. What happens to the filter pressure when you lose suction? Does it get really high or drop low?

 

[Bama Rambler]

Answer MITS' pressure question and that may tell us a lot about what's going on.
Give us the before and after pressures.

 

[gmlear]

The pressure goes up by about 6 or 7 psi.

 

[gmlear]

Sorry, I didn't include the hard numbers:

Before: 22 psi
After: 28 psi

Too much sand? I followed the manual.

 

[gmlear]

Note: 22 psi is the level after backwashing and rinsing.

 

[Bama Rambler]

If it starts out at 22 psi and goes to 28 your problem isn't the pump.
What size pump do you have?
Did you backwash and then rinse the sand really well when you replaced it?

What does your water look like?
Can you post a set of test results?