Filter delivers dirty de

[CarlD]

I don't know much about DE filters but I do know that changing media won't fix a basic problem. I'm wondering, if in addition to SO's idea, if your pump is rated for a higher output than your filter's input, which is a common problem. A 1.5hp pump CAN be too strong, especially if it's a full-rated pump (most in ground pool pumps are). How big is your pool and what kind of pump is it?

You can go to Hayward-Pools.com and look up your owner's manual. It has several suggestions of possible causes of DE going back into your pool.

[SunnyOptimism]

+1 to @CarlD !!!

Yeah, before spouting off I should have asked for more details on the pump/filter combo. I have a full rated, variable speed 3HP IntelliFlo pump. I also have the biggest DE filter possible. Even then, I run my pump on the slowest speed most of the time. I only use the highest speeds for quick vacuuming.

What kind of pump do you have? Horsepower? Single-, two-, variable-speed?

What's the sq-ft area of your filter and its nominal flow rate?

[FRANCIS]

Pool - Pacific in-ground vinyl 27,500 gal
Filter - Hayward Perflex EC65 67 gpm rating with 27 square feet effective filtration area.
Pump -Hayward Super Pump 1.5 hp single speed rated at 65 gpm with 30 feet of head resistance.
There is no 'backwash action'. The filter features a bump handle that regenerates the DE by jogging the grid - something like a piston.

[CarlD]

Pump: 65gpm with 30' of head.
Filter: 67 gpm.

So if you do NOT have at least 30' of head, your pump is probably exceeding your filter's max. In any case, IMHO, the filter is too small for the pump and you need a bigger cap filter or smaller pump.

[SunnyOptimism]

@CarlD nailed the pump/filter sizing issue. 30' of head is approximately 13psi pressure. What's your normal system pressure?

Also, I'd like to chime in on the DE issue. Your original post stated that DE was coming back through your return lines into the pool. I took a look at the filter manual and there is a built in check valve in the filter. The troubleshooting section clearly states that DE returning to the pool after pump shutdown could be a result of a bad check valve.

Have you disassembled the discharge elbow and confirmed the check valve is operable?

[SunnyOptimism]

Please IGNORE my last post!

You clearly stated that you replaced the check valve. I did not read your original carefully enough and missed that point. My apologies.

[FRANCIS]

yes - i spent 50 dollars on a check valve for nothing.