Flakes from the heater

Total hardness and calcium hardness in pool water.
Scale, calcium buildup, hard water and scaling problems.
jpgoblue

Flakes from the heater

Postby jpgoblue » Thu 31 May, 2007 12:08

Help... I have a small fiberglass pool (about 4-5,000 gallons) and spa (500 gallons). Everytime I run the heater I get little white/blueish-green flakes that deposit on the bottom of the pool/spa. The flakes only appear when I run the heater, not when it's just filtering. I make sure I keep my PH around 7.4-7.8 and alkalanity around 100 or so, as I had a problem when I first got them installed and no one informed me about low levels causing corrosion. The first few weeks or so, I had very low levels of PH and Alk, which caused the light housings to corrode and the original heater to corrode as well. But that was two years ago and I have been on top of it ever since... the new heater is about nine months to a year old. It drives me crazy that they appear and makes a mess that I have to clean everytime someone wants to go in. I have no idea what is causing them or how to get rid of them and I've had a couple of guys out to look, but they were no help... any ideas? Please...


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Postby Guest » Wed 13 Jun, 2007 17:26

What manufactuer & model is your heater?
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mr_clean
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Postby mr_clean » Thu 16 Aug, 2007 19:41

I have seen this before and it was do to the owner running the spa temp very high and using liq-chlorine. I suggested for him to use less liq-chlorine and use more chlorine tabs and check chemicals weekly. The heater was basically burning the liq-chlorine into crystal form.
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Postby Backglass » Thu 16 Aug, 2007 19:43

mr_clean wrote:I have seen this before and it was do to the owner running the spa temp very high and using liq-chlorine. I suggested for him to use less liq-chlorine and use more chlorine tabs and check chemicals weekly. The heater was basically burning the liq-chlorine into crystal form.


This makes no sense. Please explain how chlorine from a liquid would somehow crystallize and "burn", yet the identical chlorine from a tablet would not?
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Postby mr_clean » Thu 16 Aug, 2007 22:10

Liq-chlorine has salt, tabs do not, as for pissin you off, I really do not care, as like you was just tryin to help someone out..............not trying to show someone up. God forbid someone else might know something.
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Postby chem geek » Thu 16 Aug, 2007 23:55

Though bleach and chlorinating liquid contain additional salt, all forms of chlorine reduce to chloride when the chlorine gets used up so salt levels build up from all sources of chlorine. They just build up twice as quickly from bleach or chlorinating liquid as from Trichlor or Dichlor (Cal-Hypo is in between as it has some additional salt, but not as much as bleach or chlorinating liquid).

Anyway, when the chlorine is added to the pool, the chlorine and salt dissolve separately so there is no basis for saying that it is the source of chlorine that directly causes the problem. Salt pools, for saltwater chlorine generators (SWG), have far higher levels of salt in the pool, for example. Salt, as in sodium chloride, will NOT form crystals at high temperatures. It is fully dissolved in the water and will stay that way until splash-out with evaporation -- the water is nowhere near saturated in sodium chloride salt.

I think the flakes may just be calcium carbonate since higher temperatures, such as found in a heater, cause calcium carbonate to precipitate if the water is over-saturated (calcium carbonate is one of those unusual substances that actually dissolves in water better at lower temperatures). So I suspect that the combination of high pH, high Calcium Hardness (CH) and/or high Total Alkalinity (TA) is to blame and these can be adjusted so should be tested. If the saturation index is high, then the extra heat (higher temperature) from the gas heater can produce scale. The good news in this particular situation is that such scale appears to be flaking off and not just sticking to the heat exchanger which is more common. So taking care of this problem will help extend the life of the heater which would otherwise become less efficient as scale built up and the heater would ultimately burn out (or shut down from internal heat sensors).

As for the experience where switching from a liquid source of chlorine (i.e. bleach or chlorinating liquid) to chlorine tabs (i.e. Trichlor) solved the problem, that was most likely due to the acidity of the Trichlor tabs so it was the lowering of pH that reduced the scaling/flaking problem. I wouldn't say this is directly related to the source of chlorine or have anything to do with its salt content -- it is an indirect effect from the resulting pH when using the different chlorine sources. The pH can be adjusted in other ways as can the Calcium Hardness and Total Alkalinity which are also factors in the over-saturation of calcium carbonate in water.

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Postby Backglass » Fri 17 Aug, 2007 09:29

chem geek wrote:Anyway, when the chlorine is added to the pool, the chlorine and salt dissolve separately so there is no basis for saying that it is the source of chlorine that directly causes the problem.


Exactly. Thanks Richard.
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Postby mr_clean » Sat 18 Aug, 2007 12:02

Ok normally I would tell a customer using Granular or tabs for a spa only:

The white chips are calcium deposits (scale which forms on the heater elements) which are knocked off when the blowers and jets are on. This problem can be prevented by empty/refill = pool/spa water and start using a sequestering agent, such as Rendezvous PROTECT PLUS or Leisure Time SPA DEFENDER, on a weekly basis to prevent calcium and can happen with all chems reading good.

But on the above that I talked about = salt: this causes corrosion and its no joke.

The story I touched on, the guys chemicals readings were all good, he had just got a 300,000 btu pentair lo nox heater for 30,000gal pool 3 months before and pool return started throwin white chips with blue/green on edges. Also heater was set at 104degrees.

You may think it's crazy but salt is corroding the heat exchange area at a fast rate alot of the warrantys state do not hookup with salt system or warranty will be voided.
Or buy our new heater for salt pools with corrosion protection.

anyway you look at it, you have corrosion

If I remember correctly his pool & spa was only 4 to 5000 gal and a gal of liq chlorine can become alot when added and has salt in it.
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Postby chem geek » Sat 18 Aug, 2007 13:01

When I said "calcium carbonate", that is the same thing as what you call "calcium deposits" or "scale". It's not pure calcium and you don't have to use a metal sequestering agent since it will only form if you have too much calcium AND carbonate together. So it is readily managed by the proper combination of pH, Total Alkalinity (TA) adjusted for CYA, and Calcium Hardness (CH). The only time you would have to use the metal sequestrant to reduce the calcium is if the fill water was very high in CH. Otherwise, adjusting pH and especially TA will prevent scale. If one targets a saturation index that is slightly corrosive (negative), then even the higher temperatures at the heater (around 30F higher at the heat exchanger surface) won't produce scale. And in a vinyl or fiberglass pool with no exposed grout with tile, one does not need extra calcium in the pool so usually scaling is not an issue unless the fill water is high in CH (as with some well water).

As for salt causing corrosion, I have an entire thread devoted to that issue here , but it's technical. Yes, higher salt levels are more corrosive to metal and this is mainly an issue in SWG pools since the salt levels are so much higher (typically around 3000 ppm) in such pools. This is one reason why many new heaters now use titanium heat exchangers instead of copper. The blue/green edges on the white chips you saw were copper carbonate (copper dissolved into ions from the heat exchanger that then precipitate out when combined with carbonate in the water) since that is blue-green (see a picture [url]http://en.wikipedia.org/wiki/Copper(II)_carbonate]here[/url] though it will turn darker towards black as it oxidizes to copper oxide as shown here ).

I disagree, however, that the use of liquid chlorine (bleach or chlorinating liquid) would lead to high salt levels that quickly. As I said before, ALL chlorine sources will have 1 ppm FC convert to 0.8 ppm salt (chloride) and the liquid sources (as well as lithium hypochlorite) add an extra 0.8 ppm salt. So even if one were to add 4 ppm FC per day, that comes to a total of 4*1.6*30*6 = 1152 ppm salt over 6 months compared to half that, or 576 ppm, if using a stabilized source of chlorine -- and these numbers assume no splash-out, backwashing, or changing of water. And adding 4 ppm FC is very unusual except in a small hot tub (500 gallons). Usually in a 4-5000 gallons pool/spa, the daily chlorine consumption would be less than 4 ppm FC and there would usually be some loss from splash-out or backwash/filter-cleaning.

Anyway, I do agree with you that in pools that use a lot of chlorine, in terms of daily FC usage, that over years they can build up salt to the level of SWG pools and therefore have similar issues. And using a liquid source of chlorine gets you there twice as fast. One can rather easily check the pool's salt (chloride) level with an AquaChek test strip or a Taylor K-1766 (as shown here ). Of course, one can reduce the salt levels in their pool via partial drain/refill or more frequent backwashing (for filters that backwash such as sand and some DE).

1 gallon of 12.5% chlorinating liquid in 4,000 gallons would yield 31.25 ppm FC which is higher than usual shock levels. When the chlorine then got used up, the result would be about 50 ppm higher salt levels. So even this extreme example doesn't get you to thousands of ppm salt unless this happens frequently. Again, the main rule to remember is that any chlorine increases the salt level, but the bleach and chlorinating liquid (and lithium hypochlorite) does so twice as quickly, but it's still relatively slow.

Richard
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Postby mr_clean » Sat 18 Aug, 2007 13:58

and how many pools have you gone to with this kind of problem and fixed the problem?

it's not always the chemical balance as I stated when I showed up and checked them they were good.
What you say sounds great on paper but going out to peoples houses and trying to find out how they take care of there pool and if they even understand chemical balance is always fun :shock:

what happens to the people who's heaters do not have the titanium heat exchangers instead of copper. What do you tell them?

As for reading anthing you wrote about salt problems, I don't have to as I see the problems all the time with the customers who have salt pools.

I have also researched it and have been told by pool builders about this very problem and have they agreed it happens.

also when I go to someones house and their spa is throwin white chips because they take care of it, I do explain proper chemical reading etc. but working people who do not always maintain spa chemicals correctly will need something like defender.

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