Dirt coming in through the return

[Watermom]

A 1.5hp pump is big for a 15K gallon pool. It may just be pushing debris through with so much force that your filter can't catch it. How many pounds of sand does that filter have?

[PoolOwnerT]

Ok I'm reading off the filter and it says .45mm-.55mm "filter sand" 100 lbs. The pool gallon I gave earlier might not be right, I know it's a 27ft round above ground pool.

[Watermom]

I'm not the equipment guru around here but I'm pretty sure a 1.5hp pump is way over-sized for a 100# sand filter. That may be your problem. Let me have someone else confirm my suspicion.

[PoolDoc]

15,000 gallons is a reasonable figure for a 27 round pool.

However, maximum effective flow on a 16" filter is only 20 GPM . . . and your pump is pushing way more than that. But on a pool your size, you need 35 - 45 to maintain good water quality.

I don't really know the history of how AG pool filter ratings got done, but somehow AG mfgs were able to get the NSF to say that, on AG pools, you 25gpm per sft of sand surface was OK, but on IG pools, you couldn't go higher than 15 gpm. It's not like water in AG pools is different than water in IG pools, so there is some serious bogus-ness in those ratings!

In my experience, for really good sand filter performance, you need to be in the 12 - 13 GPM per sft range. On your filter, that would me around 17gpm!

Having an oversized pump and an undersized filter is a common, common problem on AG pools. You need to either:
+ step up to a 24" sand filter, OR
+ throttle your flow back to 20 gpm.

The first is a MUCH better option. If you do the second, you'll need to reload sand into your filter after you get the flow throttled. You've almost certainly blown a lot of your sand out in the backwash!