Filter blowing dirty water


Well-known member
Apr 3, 2011
Katy, Tx
I've had the pool for 7 or 8 years, was going great until April this year, couldn't keep the water clear. It was clean, just cloudy. Talked to a few pool people and they said it was time to change the sand. I did, it was great, nice clear and beautiful, well for 4 months, now here we are in August and its green and can't get it clean. The Ph is good, Chlorine is high, etc. So i decided to dump some coagulant in and let it sit overnight then use the hose/filter to vacuum it. Was going great, but I forgot to turn it to waste, but that turned out to be a good thing. I look down and I'm blowing dirty green water right back into the pool.

So, herein lies the questions. Is it possible that the filter is just overloaded? I did a backwash until it was blowing clear, rinse until clear, tried vacuuming again, same thing, blowing dirty water. Ok, is there something that is bypassing the filter or do you think I have a broken lateral? As I said, it worked great for 4 months after changing the sand.

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
"11", you're probably not going to like this answer. But the advice you received was poor. Not surprising from a pool store. The cloudiness and green was probably algae in which case you needed to use the SLAM Process. Sand doesn't go bad UNLESS someone adds a pool store product like floc or clarifier, doesn't vacuum to WASTE, and it makes it to the sand. It appears you did that correct? If so, now the new sand is probably bad (gel and sticky).

It's unfortunate, but I suspect new sand followed by the SLAM Process is your best remedy. Once you pass all 3 SLAM criteria, make sure to keep the FC and CYA balanced together as noted on the FC/CYA Chart to avoid the cloudiness or green in the future.