Chemical Levels. Strange to me.

What is floc, clarifier, stabilizer, cyanuric acid,
algaecide, brightener, dichlor, sodium hypo,
sodium bisulfate, ....??
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Chemical Levels. Strange to me.

Postby msikes » Tue 04 Sep, 2007 01:44

I have searched these forums for a similar problem to mine. I find close, but not quite the same. So I hope that maybe someone has seen or experienced what Ihave going on, and can shed some light on my problem. Firstly, as suggested I went out and purchased a good Taylor test kit, and actually had the local pool supply do it too to verify my numbers.

My pool has a baja step that developed some crazing. At the request of the plaster company, we had to keep the PH below 6.8 for a couple months. It did not fix the problem. It became worse, and they are going to redo it (step) after swim season. Since then however, we had the problem of flakes, then the generator died and was replaced, and now minor scaling. There is now a sandpaper feel to the plaster and a white hazing to the plaster in some places. So bad that when the kids swim, they get bloody toes now. It is really sad.

I have lived with pools all my life, and this is the first time I have had this problem. What I dont get is how my Calcium can be so high, and the TA so low?

Here are my numbers.

Pool (6 months old, Plaster, Pentair Salt system, 20K gallons)
PH 7.2; TA 70; Calcium 700; CYA 25

Fill (City Supply)
PH 7.2; TA 190; Calcium 300; CYA n/a

Any suggestions to lower the Calcium? Can I even fix the 6 month old Plaster to get it smooth again?

Any support is appreciated.

Matt


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Postby mr_clean » Tue 04 Sep, 2007 17:01

Wow, I would talk to builder about resurfacing pool for free with their advice on lowering PH below 6.8 for a few months.
When doing this to remove crazing, which I have never seen work it is like acid washing your pool walls which will etch walls and make a little ruffer. But, "a few months" this is going to etch even more and make it like sand paper. No wonder your kids toes bleed.

Replacing generator? Did you mean heater? With corrosive water do to very low PH & Alk. your heater exchange I would think got eaten away/disolved.

When you say Calcium 700, I assume CH-Hardness 700. With heater being eaten away adding metals and plaster being eaten away is why test results went up. Until pool builder drains water, you can add a sequestering agent/metal remover to water and do not use anything with calcium in it.



[/quote]
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Postby chem geek » Tue 04 Sep, 2007 18:41

Something doesn't seem right about the numbers you posted. With the fill water having a TA of 190, I am surprised that your pool's TA is down to 70. Also, the SWG will tend to cause the pH to rise so having the pH at 7.2 would be unusual. Perhaps the fact you were trying to keep the pH down at 6.8 had you add so much Muriatic Acid that you effectively lowered your TA level over time (that would make sense, at least).

So even with your high Calcium Hardness of 700, you wouldn't normally have a scaling problem in an SWG pool with the pH down at 7.2 and the TA down at 70. I can certainly see that when you first started out, you had a TA closer to the fill water of 190 and probably a higher pH above 7.5 and that would cause quite a bit of scaling. So the way I see it, you used to have a terrible scaling problem and the builder had you keep the pH low which mostly just caused the TA to drop (when you added acid regularly) until the TA got so low at which point it started to dissolve the plaster.

As mr_clean pointed out, the problem with this technique is that it is not selective. Dissolving plaster via corrosive water will not just dissolve the previously formed scale but will dissolve in unusual and not smooth ways.

Anyway, as for water balance, if you keep the TA low at 70 ppm, you are actually in pretty good shape as long as you keep your pH at or below 7.5. You could even go lower in TA down to 50 (through continued addition of acid with aeration -- see this post for the technique, though you could just see how much the pH wants to rise at your current TA of 70) and then maintain a pH of 7.5 to 7.7 and should find that the tendency of your pool's pH to rise will be significantly lessened. The low TA and high CH balance each other out with respect to calcium carbonate saturation (i.e. the tendency to dissolve plaster vs. have scaling).

Unfortunately, I don't have a good answer with how to fix the rough plaster surface other than replastering or otherwise resmoothing it -- I don't think any chemical treatment will handle that well.

Richard
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Postby msikes » Wed 05 Sep, 2007 00:30

Thanks for the replies. Not only a reply, but two great replies. Much appreciated.

Generator in my post= Chlorine Generator :)
Calcium= Calcium Hardness

As you stated, yes I had to add alot of acid to keep the PH down. I had a feeling it was going to do damage to the plaster. Now my worst thoughts are confirmed. Just to make the Baja Step fun for my 1 year old I had to wet sand it so he could play on it without being hurt.

How can I tell if my heater has been damaged? Do you think I should hire a professional to come out and diagnose it, or is there a way I can tell? I am extremely handy and can pretty much do anything. Just time is what I lack!!
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Postby chem geek » Wed 05 Sep, 2007 01:16

If your pH didn't drop below 6.8, then even with the corrosive water balance I think your heater will still be OK. The water balance is technically only corrosive to plaster -- in that it dissolves plaster if not saturated with calcium carbonate. For metals, such as found in a heater, the pH is the far more important variable as is the salt level (high salt levels are more corrosive, due to increased conductivity and for stainless steel high chloride levels are more corrosive). Though 6.8 is more corrosive to metal than 7.5, it's not nearly as bad as more acidic conditions sometimes found when people put Trichlor pucks in the skimmer -- something that should not be done (at least not when the pump cycles on and off).

The problem is that most pH test kits don't show anything below 6.8 so a reading of 6.8 could be lower than 6.8 and that could be damaging to the heater. If you only added enough acid to get to 6.8 and not lower, then your heater is probably fine.

If you get your pool water tested for metals, then if there is copper in the water, it is most likely the heater. If the heater is newer, then it's more likely made of a titanium alloy and much more resistant to corrosion so should be fine.
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Postby msikes » Tue 02 Oct, 2007 12:34

My heater is a 6 month old Pentair 400,00 btu. You think that they are titanium alloy?

I am goijng to take my water to be tested for metals also. I am going to call my pool builder today. I will let you know the outcome.
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Postby Guest » Tue 02 Oct, 2007 19:00

I'll bet it's titanium. Almost all modern gas heaters are. And as I said, I would doubt very much that 6.8 would cause much of a problem. It's easy to get the water tested for metals (copper, iron) so you'll know soon enough.
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Postby mr_clean » Tue 02 Oct, 2007 20:17

I'll bet it's titanium. Almost all modern gas heaters are. And as I said, I would doubt very much that 6.8 would cause much of a problem.


I hope he does not have heater problem, but not all new heaters automatically come with a titanium heat exchanger. When buying a heater you need to know what your looking for or ask for info. Alot of people still buy heaters with copper heat exchangers, nickle & titanium are better.
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Update

Postby msikes » Fri 16 Nov, 2007 01:36

Pool has been replastered. Heater is fine. This whole thing has been such an ordeal.

The plaster company now refuses to tell me anything about starting up the pool now. They dont want to be "responsible" for me following their directions. I am really disappointed in them.

I am searching the forum for startup tips now. Any tips are appreciated.
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Postby mr_clean » Fri 16 Nov, 2007 13:15

here is the info you can print out to do startup for new plaster, if you have automatic pool cleaner do not put in for 6 weeks so you do not make any spots/marks.

start-up info

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