Sand in pool

[PoolDoc]

Glad we could help!

[Marin]

Sorry for coming in late on this one. Only had time to skim the 2 pages, so if I've overlooked too much please ignore me.
First off, if it's truly sand, it's not coming from your pool finish. There are no plaster type finishes that use sand. I could be wrong because I'm not familiar with them all, but that's my educated response.

A few years ago we replastered a pool and the guy started seeing sand in the bottom. He accused us of messing up his sand filter. The equipment pad was 25' away and we'd never touched it. After a lot of arguing & investigating, we found out he was using some bargain basement chlorine tabs that had sand filler in them. Chemicals desolved in the water, leaving behind sand. Just a thought.

Another scenario is if you have sandy soil and a leak in your return lines, it could draw in sand and deposit in your pool. I think that's very unlikely.

Third idea, which I've asked of others in this situation before, is if you have kids and a sandbox.

[nefretrameses]

Coming in late is no problem for me.

"Sand" is the best term I could come up with. It's really quartz crystals (i.e. sand) but is includes green and blue particles that are the same color as the "specks" in the finish. I'm not sure what tradename the finish is since it was before my time, but it's an aggregate of quartz crystals - mostly white, but with blue and green crystals in it as well. If it was just sand, I'd be looking for an external source, but the presence of the green/blue particles (in what I see on the bottom of the pool and what I wash out of the cartridge filter) convinces me it's the pool finish. Also, if I brush with a SS brush, I can get a small pile of the stuff below the brushing area.

I was using Tri-chlor tabs from Sam's Club (which I believe are a recommended brand if you are going to use Tri-chol); but I have switched to Cal-Hypo (while I raise my CH a bit) and Liquid Chlorine - so it's not that. No sand filter or kids with a sand box, but it is sandy soil for sure.

Like I told Doc, my pH was below 6.8 for an unknown length of time and CH was 180 or less as well - before I found this site.

I'm hoping having my water balanced on the slightly + side of the SI scale will eventually stop this from happening. It does seem to have slowed.
John

[PoolDoc]

It's really quartz crystals (i.e. sand) but is includes green and blue particles that are the same color as the "specks" in the finish. I

That pretty much narrows it down, to dissolved pool surface.

If you maintain your water, the rate of deterioration will slow, but won't immediately end. The reason is, aggressive water conditions penetrate into the finish, weakening the matrix that holds the quartz particles. Where the matrix dissolves completely, the particles are immediately released. But where the matrix is only weakened, it may be some time before those particles shed.

FWIW, I'm pretty sure some of those surfaces can be refinished merely by regrinding them -- if the remaining surface material is thick enough. Marin would probably be able to either confirm or correct this, and possibly point you in the direction to carry it out, if it's possible.

[nefretrameses]

Thanks Doc & Greg.

It makes sense that aggressive water is the root cause. Hopefully the damage isn't "fatal". I'll keep brushing and maintaining my water balance.

Our swim season will end sometime in mid or late October. Would it be of any benefit to raise pH or another factor so my SI is even more positive during the winter? The pool stays open.

[Marin]

They make underwater polishing equipment (not even close to cheap) for that purpose.

I thought I'd mentioned earlier, maybe I dreamed it, or it's the fatigue & allergy meds, but throw away that SS brush. It's slowly damaging your finish (maybe even causing "sand"). Get a nice high quality nylon brush. SS brushes are too aggressive for nice finishes. Older pools with a bad surface and algae? Go for it. Otherwise no.

[nefretrameses]

I mostly use a nylon brush for routine cleaning, but I have the SS brush for the occasional heavier need. The surface is at least 7 years old and a little rough in spots. The previous owner said refinishing after 10 - 12 years would not be unexpected. Don't know if that's right or not. If so, I'd expect to refinish in 3 - 5 years. I'd probably want to do it anyway to fix the "pockets" that in in floor pop-ups are in.