Water eating away at rockwork

[dmpacey]

Mods: apologies if this isn't the correct forum...

The finish on the rockwork columns in our pool is being eaten away by the water in our pool. In the photo, you can see the difference the rockwork's appearance above the sheer and below it. Guess I should have turned off the sheers when SLAMming the pool in the past (I'll remember going forward). I've been finding tiny granules and pebble-like "rocks" on the pool floor under the columns and want to stop this before the crumbling goes too far. Any ideas? Would something like paver sealer work?

To be clear, these aren't real rocks. They're concrete or another kind of aggregate that have some kind of finish that makes them look nice. Not sure what, we didn't build the pool.

 

[djdonte]

Post some recent test results. If I'm not mistaken low CH can cause leeching from plaster and concrete.

 

[mknauss]

Can you post your pool water chemistry results?

 

[dmpacey]

Earlier this morning the FC was close to 0 because I've been draining water a little at a time in an effort to lower my CYA and using the pool water to soak some trees in my yard (I'm in Phoenix) and didn't want to give them a bunch of chlorine. But this morning the water wasn't looking great, so I added two gallons of liquid chlorine and a pouch of pool shock (I bought a box 8 years ago at Costco when we moved in and before I found this site, still working through the 24 pouches).

Measurements this afternoon:
FC 11.0
pH 7.4
TA 90
CH it was 140 when it turned from red to clear. I stopped when it was still clear a 400 and hadn't turned blue
CYA 120 (yes, I need to lower this)

 

[mknauss]

How do you chlorinate?
What was the 'shock' you used?

 

[duraleigh]

My guess is the faux rocks are being bleached out by the chlorine in your water and I doubt there is anything you can do about that. You MUST have chlorine in your water. However, it might also be calcium build up from that waterfall trickling down the surface

Now, you say it is crumbling....(and that possibly can be addressed) Can you tell for sure (by breaking off some small pieces) that you are getting small chunks and not just tiny pieces of sand that will come off most any concrete surface?

Can you post a pic of the crumbled pieces?.

Looking more carefully at that good pic, I believe it is calcium build up from the waterfall and not bleaching.

Great looking pool.

 

[dmpacey]

This "shock" was some granules in a Clorox-branded pouch. I've had the box for eight years and still not through the 24 pouches that came with it -- usually shock with liquid chlorine. I only use these pouches now after monsoon rains and dust storms.

I chlorinate with liquid chlorine during swim season. In winter, I put pucks in a floater, which, I know, raises my CYA.

 

[dmpacey]

A closer photo, where you can see the finish of the faux rock below the sheer has been eroded, exposing the aggregate. Would concrete sealer work to slow or stop this?