saltwater pool question

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

saltwater pool question

Postby vin » Thu 24 May, 2007 11:54

Hi all - first time poster here.

Just had my pool water analyzed & everything was fine, except the guy said my calcium hardness is low & I have to add 25# of "hardness plus". I seem to remember the same thing happening last year when I opened my pool. I run a saltwater system in my 20,000 gal. inground pool, so I'm wondering if that's got something to do with it. The guy said the calcium is necessary in order to prevent corrosion of my pool heater.

Does this sound right? Don't the salt (softener) & calcium (hardener) have opposing effects on the water chemistry? Will my increasing the calcium hardness have an adverse affect on my chlorine generator?

Thanks for your time!


Buggsw
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Postby Buggsw » Fri 25 May, 2007 20:49

What is your pool surface? Plaster, vinyl, fiberglass, etc?
Guest

Postby Guest » Sun 27 May, 2007 18:39

Pool is vinyl - thanks.
Buggsw
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Postby Buggsw » Mon 28 May, 2007 02:48

You didn't say what your CH test reading is. Is the water in your area considered soft or is your fill water source going through a water softener in your home? I think most areas regular tap water is usually not soft and would be above 140 ppm. You could run a test on yours to find out what your fill water readings are.

The recommendation for a vinyl pool is 80 - 200 ppm, though there are some people that scoff at even worrying about low calcium with a vinyl pool, others argue that proper water balance includes proper levels of CH, regardless. Pool heaters add another element to it.

I don't have a heater, so am not familiar - but I know enough that you don't want to have any increased corrosion in them. I also have read many times that corrosion is caused more often by acidic water (low pH), but yes very low CH can cause it, as well. Too high of CH causes scale, which is also not good for pool heaters.

You might want to check with the heater manufacturer, to get their recommendation.

I found a manual for one pool heater manufacturer online, that says if you have heat exchanger corrosion it voids the warranty. They give a general guide of:

pH 7.6 to 7.8
Total Alkalinity 80 to 120 ppm
Calcium Hardness 150 to 250 ppm
Salinity 4000ppm
Guest

Postby Guest » Wed 30 May, 2007 13:21

Thanks for your insight, Buggsw :) . I didn't ask the guy what the exact number was, but I will next time. I went ahead & added the recommended dosage & all seems well as of right now. The pool is open, balanced & looks great. It's funny though as there seems to be some unsolved mysteries when it comes to saltwater systems. Another little issue that I've been dealing with on mine is the ph constantly creeping upward & every so often I've got to add a few pounds of dry acid. I did some research & it seems to be a common occurance in saltwater pools although no one seems to be able to explain why it happens. I guess until these systems become more mainstream, some of these answers will continue to elude us.
me_too

Postby me_too » Wed 30 May, 2007 18:39

Anonymous wrote: I did some research & it seems to be a common occurance in saltwater pools although no one seems to be able to explain why it happens. I guess until these systems become more mainstream, some of these answers will continue to elude us.

It has to do with production of sodium hydroxide from the cell combined with (nitrogen? I have to look at the equations) outgassing. These elements combine to raise the pH.
Buggsw
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Postby Buggsw » Thu 31 May, 2007 00:26

Yes, I think it is pretty normal to have to use acid a little more frequently.
In fact there is one SWCG that is called AutoPilot Total Control that includes a big tank which dispenses acid along with the system generating chlorine from salt. I'm saving my pennies for that one - I'd love to not have to handle acid manually any more than to refill the tank every so often.

What is your TA? If your TA is too high or too low, you will see greater swings with pH.
Guest

Postby Guest » Mon 04 Jun, 2007 12:06

TA is 90. I also try to be diligent about keeping the pH at the lower end of the scale - around 7.2-7.5. This seems to keep pH creep from getting out of control.

The pool is dialed in pretty nicely right now w/ the SWCG working at only 20% to maintain a chlorine level between 1.0 - 2.0. Although it just rained about 3" last night, so that's probably changed things a bit ;-).

Thanks to all for your comments.
Guest

Postby Guest » Tue 12 Jun, 2007 20:06

Acidic pool chemistry WILL over time breach the inner wall of a copper/cupernickel heat-exchanger (condensor); which results in complete failure of a heatpump (aka its now scrap, a flooded unit). A ph of 7.4 is perfect. However, w/a titanium coil, chemical damage of any type is basically nill. Also, salt content of about 3000 ppm is the same as the human tear, which is perfect.
Griz

saltwater pool question

Postby Griz » Fri 24 Jul, 2009 21:20

To all, I have been a proud owner of a beautifu vinyl 20,000 gal salt water pool for 2 years.
Two days ago I had my water tested at the local pool suply store. All the chemistry was in ballance except I was told my water softness was to low 120 ppm. The clerk said to add at least 25# of water hardner. I did some research and learned the pool hardness should be between 200 - 400 ppm. I proceeded to add 35# of hardner which should bring the pool to near 250 ppm. Befoe I added the hardner my CH was 2.5 . After I added the hardner the CH measured 1 . I have been strugling to get the CH back to 2.
It's almost as if my generator stoped making CH. Although I can measure higher levels of CH pumping at the returns. I am concerned the hardner has changed my pool chemistry and would like to know how I can get it back to normal.

Thanks for any response.
Griz

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