Coping stone has flaked and spot welded itself to the bottom of the pool - help!

[ZapRowsdower]

Hello all, I work for a pool cleaning company located in the Southern California area. I battle a ton of stuff, but for the most part the other guys/my boss have seen everything. This one has us stumped though.

We have a client that has granite coping stones near the pool (more as the patio floor actually). They have started to chip from all the use and flecks of them have started to fall to the bottom of the pool, mostly the steps and spa. Now I find that they have spot welded themselves to the bottom of the pool and won't come off! We're all stumped about how to get them off.

The worse part is that I have another client (one that's much more particular), and their spa is doing the same thing. Does anyone have any chemicals that we can use that will loosen them, or some remedy. It's going into summer and I want them to look great for the clients. The strange thing is that it's only these two, the rest are just fine.

If you guys need any more info let me know. Thank you all for your help!

-ZR

 

[Patrick_B]

Welcome to the forum!

I really don't think a chemical addition is a solution because you'd be doing something to the whole pool and perhaps damage the finish. And I don't know it would work. I could be wrong, but I think mechanical removal is the only answer.

Why it happened is a wild guess, but nothing outside a reaction beteween the two materials comes to mind.

 

[ZapRowsdower]

Hmm, got it. I figured there wouldn't be anything chemical wise to add, but worth a shot. Dunno why it happened either. The two pools have nothing in common, other than the fact that there is some sort of coping stone near it that flakes off. I'm in the process of a full saturation index check on all the pools, so I'll work the chemicals over top to bottom and see if there is something in common with them.

PS mechanical removal, as in sandblasting or something?

 

[Patrick_B]

I was thinking chipping them off, but if you are in CA It seems unlikely you'd have an index low enough to cause this, so maybe it's an oversaturation induced reaction. There is only one index that we watch, and some people pay little attention to it. Some are anal retentive about it, but in most cases you can ignore it with the overall parameters we suggest. We really aren't here for the pool industry however, as the majority here are just pool owners helping other ones regarding DIY pool care. Some of us have different backgrounds that apply, and a handful of service people are here as well. I would personally like to figure this out for the pool owners, but it's also an interesting problem I think. You're going to find something in commom with both those pools in one form or another. Whether it's the type/makeup of the materials "welding" together, water chemistry, or both and possibly more. Perhaps this subject has come up before, but I don't remember seeing it. I am curious what you have found Chemistry wise so far though, so have you run a full set on both?

 

[woodyp]

I'd contact a local stone company and put the question to them...................

 

[ZapRowsdower]

Awesome, thanks again all. Here's the info for the two stops:

Alkalinity 71, Calcium HI, Cyanuric Acid 84, Temp 66. (SI checks out at 0.13)
I think the stone is actually slate.

The other is:
Alk 87, CH HI, CYA 76, Temp 66 (SI 0.29)
This place actually has the stone as seats IN the spa.

NOTE: I can't actually find what the "HI" means on this tester. I did a dilute test and it hit 450, so it's safe to assume that it's around 900ish. This is California though, I have 8 stops that say that. It's a work in progress...

Also I'm using the Color Q test kit to test these just for the SI checks, for the pH and Chlorine I use the Taylor Test Kit. They both are epic for testing, btw!

The two pools have only one thing in common, I have to fight high pH constantly.

As for the help, I'm not looking for miracles. I'm more looking for someone who has ever seen this before! With the amount of sandstone flakes that I have had to fish out of pools you think I'd be dealing with this 24/7, but nope, just these two. Strange.

As for calling a stone company, great idea! We have a few around here that I could contact. Thanks again!

-ZR

 

[pooldv]

My theory is that there is scale forming on the pool surface and the stones are getting embedded in the scale while it is forming. A little muriatic acid would dissolve the scale and release the stone chips. High CH and high pH supports the theory.

 

[ZapRowsdower]

Thanks Pooldv, looking over all the other SI checks from my other pools also seems to support what you're saying. Next week I'll do a bit of testing with the muriatic acid on an out of sight spot and see if that can clear it up with a bit of elbow grease. The good news is that the pH is usually high so the worst that can happen is it'll keep the pH down where its supposed to be.

Thanks again all!

 

[Sammy2]

You didn't report FC, CC or pH on these. I'm just figuring this all out myself but I think if you get that SI below -0.1 they just might come off themselves as you pull the calcite scaling out of the pool and from bonding the stone chips to the plaster.

 

[tstex]

Slate and calcium based stones in a scaling type environment comes to mind as pooldv stated. It's precipitating calcium bonding when it hits the floor. make sure that the MA H2SO4 does not come in contact w any thing like travertine, marble, granite, etc, or you will have BIGTIME etching and replacement of stone.

CA is a beautiful place, but the hard water [High CH readings and low pH's] just demonstrates that everyplace, no matter how nice, always has it's +'s & -"s...

 

[chiefwej]

You could try what my pool builder did for a trouble spot. Put a PVC pipe over the offending spot and pour a little MA down through the pipe. This confines the MA treatment to the spot. How much MA and how long to leave it in place, I'll leave to your best guess. If its calcium it shouldn't take long.