DE & Dirt back in pool

[duraleigh]

Confirm that the dirt is coming from the returns. Put something over the returns very fine like panty hose to catch anything. If that's the source, your filter is not working properly.

[matt4x4]

Number ONE mistake (can't even call it a mistake though) people make with cleaning their pool is......
They vacuum too fast, unless you move your vac head about 1" per 3-5 seconds, you WILL end up with a "new" pile of dirt, actually it's an OLD pile of dirt.
When you vac your pool, you stir up the settled debris, this debris mixes in the surrounding water and "DISAPPEARS", but unbeknownst to you, it's not getting sucked up and filtered. Once you're done, you sit back and say to yourself "WOW, what a clean pool!", what you don't know is that there is a ton of dirt currently suspended in the water, but the particles are so small you can't see it until it settles in bunches - voila - your dirty pool the next day.
Nothing you can do about it other that go REALLY slow, and that will extend your vacuuming from 1 hour to 5 hours - your choice!

[JohnInSoCal]

I recenly had a DE back into the pool problem. I just watched the return very closely, there was no mistaking the DE coming back into the pool from the return. Turned out to be a hole in one of the grids and this was a brand new hayward DE 60 filter. I had to totally dismantle the filter to find it though, it wasn't easy to spot until I took it all apart. Also try and watch the return right as you turn on the pump as mine usually stopped after 5-10 seconds.

You mentioned 1 1/2 HP pump but which hayward filter do you have ? It's probably oversized just like mine is and you are probably exceeding the flow rate. I am going to change impellers to reduce flow rate. Here are the general culprits for DE back into the pool in no particular order

1) hole in fabric covering grids
2) crack in manifold somewhere
3) pump oversized
4) check the fabric around the air relief valve, make sure it's tight and without holes.
5) faulty multiport valve not seating properly, try moving the handle around and see if it helps (while pump is off)
6) check the outlet o-ring

good luck