Autopilot and Salt water eating plaster and using acid

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ewsb

ewsb

0
May 26, 2007
65
Northern VA
Pool Size
17000
I have had the following problem for 4 months. PH is dificult to maintain and the pool (15k) uses 3/4 of a gallon of acid a week (even in winter).

Initially the plaster had a tremendous amount of scale from high PH as the use of PH caught the pool company off guard. The company emptied the pool and sanded the plaster (a very smooth specialist finish) back to its original smoothness and color.

However, the pool continues to use acid and the plaster seems to be discoloring again and even becoming damaged. The pool company has been told that the problem is salt and the salt water cholorinator. Can anyone help as this is a big problem.
 
There are a couple of things that could be going wrong. We really need a full set of water test results to be able to tell which one applies here.

SWG systems can cause rapid rises in PH when the chemistry isn't balanced properly. High PH in turn can cause calcium scale to form on the plaster, turning it white and rough. With a little more information we can tell you how to avoid these problems.
 
Your problems stem from improper water balance. Read the sticky on water balance for SWGs and you will get some info on what might have happened. Without knowing your water testing history I will venture to guess that your TA is too high and/or your CYA too low for a salt pool. Both these factors can contribute to ph stability problems and the formation of scale depostits. With proper water balance these problems can be greatly minimized!
 
CYA low - TA looks good

Thanks to all for comments. I am using the Taylor 8 piece testing kit so while it does test for TA etc, it does not test CYA. I used a strip tester for that and it appears to be very low. PH is 7.4. TA is 80. FC is normally around 3 although I note today it is almost 1 (I did reduce the amount of time for the chlorinator this week). Given we have never used Chlorine - I guess the CYA is Zero.
 
You really need to get numbers for CYA and CH. Buying a high quality test kit is the best investment you can possibly make in your pool. I recommend TF Test Kits, see the link in my signature, and the Taylor K-2006 is also a great kit. It is also possible to get your water tested at most pool stores, though many of them take that opportunity to try and sell you things.

With a SWG it is important that CYA be between 60 and 80. If your CYA is really zero that would be a serious problem. Don't just add some CYA without getting the CYA level tested. While it is easy to add CYA, it is very difficult to remove it if you add too much.
 
ewsb said:
Thanks - amazing to me that the pool builder didn't do this.
Click to expand...
From my experience I have found that most pool builders know very little about water chemistry or the proper way to set up a salt pool. I even has to alert the manufacturer of one very popular SWG about the number of pools I was seeing built by one particular builder in my area that were NOT set up properly (No CYA, among other problems). The manufacturer promptly arranged a training session for this builder and his staff. (Thanks 'You know who'!). I have not seen the problems since to the same degree but I have seen pools built by three other builders in my area with SWGs that also are not being set up properly. Part of the problem is that new owners do NOT read the manuals that come with their equipment and take responsibility for making sure their water is properly balanced and that their equipment is set up properly. I know we all assume the builder takes care of that but most don't. Many don't even do their own startups but subcontract this out (often to the low bidder! think about that!)
 

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You might also want to test the PH and TA of your tap water, before it hits the pool. If the tap water is far off on either of those, it could be throwing the pool off. Not much you can do about it, but it would be good to know.
 
A latest update; I am removing the saltwater system as I have now replaced 2 raypak natural gas heaters over the past 4 years (and raypak have advised me that it was the salt water that corroded the systems)
 
So, has Raypak officially stated that their equipment cannot be used with a saltwater pool? I have never heard this before and I know there are thousands of heated pool that have successful SWG's.
 
No - as per my note they never said that - they said the salt water had caused the corrosion - (also noting the pool runs 12 months of the year). I have had an ongoing issue getting the salt water system to stabilize and I also now find that no 'sacrificial' anode had been installed which Raypak does advise if you are going to use a SWG. Even though we can do that, I just don't want to take the chance or the hassle as it has been too costly over the past 4 years.
 
Raypak is just trying to get out of honoring the warranty. That is a common problem with heater manufacturers and there is usually nothing you can do about it.

If you kept your salt at the usual SWG levels, around 3,000 ppm, there is no chance at all that the salt contributed in any significant way to your heater problems, sacrificial anode or not. On the other hand, heaters are quite sensitive to low PH and can easily be destroyed by ongoing low PH.

It would be worth your while to figure out what has actually been going wrong, otherwise the problems will simply continue, even though you have removed the SWG.
 
The disproof is in the thousands of salt systems with heaters without problems. As a manufacturer, it's common for other manufacturers of equipment, pool contractors, service companies, etc, to blame salt systems due to a lack of knowledge, or it's just easier to put the blame on someone else. We hear it all the time.
If you consider that pools running 12 month seasons, with Sodium Hypochlorite, and are not regularly partially drained/diluted, the salt level will get to 3000 ppm, the level of salt chlorine generators, within a few years. However, you won't hear the heater manufacturer void warranty and blame salt from sodium hypochlorite maintained pools. Why's that?

Copper, or Cupric Nickel heat exchangers, are prone to damage from low pH conditions (as Jason mentioned), but also high chlorine levels, and improper water chemistry balance (per saturation index). The only direct results from a salt system are if you maintain salt levels in excess of 6,000 ppm, or if there is already an electrolysis issue. Salt will increase the conductivity of the water and accentuate the electrolytic effects.
 
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