Gritty Deposits on the Bottom of my AGP

ghall6292

Bronze Supporter
Jun 10, 2018
138
North Central PA
I have a 24' x 52" AGP. I am finding small areas of a tan gritty substance on the floor of the pool, mostly the 2 feet nearest the edge. When I vacuum, I have to go slow and scrub over these spots to make sure I get it all. It doesn't just disappear in a poof. I brush the walls and brush and vacuum the floor once a week, life permitting. It doesn't form a cloud and disappear in a poof. Our pool gets full sun on 270 degrees of the 360. There are very few of the deposits on the shady area. The deposits are heaviest just before the circular motion of the water gets back to the skimmer intake, although there is a small amount around the entire edge. Could my sand filter be leaking sand back into the pool?

In the past couple days I removed my ladder, disassembled it, and power washed it; I let it dry in the sun and put it back together and reinstalled it. I also took out the skimmer weir and took the foam out of it and soaked both the foam and the weir door in 50/50 bleach and water, along with the skimmer lid and basket. I then scrubbed all parts (plus the skimmer bowl) with a brush and reassembled it. I run hair nets in my skimmer and change them out at least every other day. Mostly just catch bugs and leaves, once the pollen drop is over. We have no main drain nor any lights. My last item to do will be my solar cover, and that is a tomorrow project. It appears to be in good shape, though. I'm going to do an OCLT tonight, just to see what it shows. Should I remove the cover overnight or leave it on to keep the warmth in? Would leaving it on mess up the OCLT? It's been getting down into the mid 50's the past few nights.

My chemistry has been very consistent. FC: 4.5-7.5 (no SWG,), CC: 0-0.5, CYA: 40-50, pH: 7.5-7.7, TA: 80, and CH: 125 (vinyl pool.) My water is very clear; you can tell the heads from a tail on a dime all the time. I admit I'm kinda puzzled. :confused: Any thoughts would be appreciated. Thanks!
 

cowboycasey

Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
8,647
Southern OK
Pool Size
15000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
CircuPool SJ-40
Go ahead and do the OCLT.. You can leave the top on... It could very well be sand... CH at 125 I doubt it is calcium buildup.. sounds like sand to me :)
 
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CraigChing

Gold Supporter
Jun 15, 2019
189
Plymouth, Minnesota
Pool Size
22000
Surface
Vinyl
Chlorine
Liquid Chlorine
Do you have a sand filter? I get what sounds like you’re getting and for me it’s definitely sand. I can dive down and touch it with my fingers and pick it up. I notice more after I backwash. I don’t get much so I’m not super worried, but it annoys my clean pool OCD 😀
 

ghall6292

Bronze Supporter
Jun 10, 2018
138
North Central PA
Well, I completed my first ever (yeah, I know... don't say it out loud!) OCLT. Started at 8:45 last night and completed at 6: 45 this morning. The results are as follows: Last night- FC 8.5, CC 0. This morning- exactly the same! Soooo...Sand it is! :D Now I have to figure what's causing it to leave its wonderful comfy home inside my filter!

I really normally only do a couple backwashes a year, probably because of always having a hairnet in the the skimmer basket. But this year, because of the almost constant thunderstorms we've had, I've had to keep doing water dumps to lower the level in the pool; as in water right to the top of my skimmer housing a few times. I'll admit to using the opportunity to do extra backwashes instead of just sending the water directly to waste. (My personal OCD; I HATE to waste anything; even the word annoys me! LOL.) Probably it's what's causing the sand to be more visible. I guess if the filter pukes out a tiny bit of sand on each backwash, and I only do one mid-season and one when I close, I wouldn't normally see the sand. On the plus side, I haven't yet added any water since last season, which is nice because we're on a well.

BTW, Craig, I totally get what you mean about the clean pool OCD.
 
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