CYA disappeard ove the winter?

[PolareNJ]

Problem: High salt levels in pool.

As this thread testifies, we went through many challenges with our pool this year, but with the support of TFP, we have gotten the metrics under control. One odd thing that I mentioned before, we thought the pool tasted salty. When I went to pick up more liquid chlorine from the pool store today, I had the water tested and the metrics are in line with my testing using the TF-1000 kit. When I mentioned the salty taste, the assistant at the pool store used two tests used on salt water pools and both showed salt concentrations of 3600 - 3800, which is high for salt water pools (the equivalent of 500 lbs of salt?). No one can explain where this salt came from, but their suspicions are the large amount of liquid chlorine used during the spring. Another note: It seems that the salt taste of the water is very noticeable when the sun is out, and after dark there is hardly any taste at all. Some chemical reaction going on?

Our metrics are (from TF-1000 test kit)
pH = 7.5
Alkalinity = 80
Calcium Hardness = 400
Free chlorine = 5.0 ( we add liquid chlorine every night to bring it up to 7 to withstand the burnoff from the pool being in the pool all day)
CC = 0
CYA approx. 40
Water temp: 72 in the morning, 76 by 5 p.m.

We were hoping to start closing the pool today, but am not sure what to do now about the salt. Several questions:
Any ideas of where the salt came from? Liquid Chlorine?
Can we close the pool without emptying and refilling and deal with it in the spring? We are on a well, and this would be a major undertaking in itself, and to refill and then get the water chemistry right would take some time.

Thanks for any help.

 

[chem geek]

For every 10 ppm FC added by chlorinating liquid or bleach, it increases salt by around 17 ppm after the chlorine is used/consumed. With 2 ppm FC per day chlorine usage, that would be a salt increase of around 100 ppm per month. If you had higher chlorine usage or were doing extended SLAMs of the pool, then you would have added more salt, but you likely started out with somewhat high salt at the start of the season. Note that ALL sources of chlorine increase salt because chlorine becomes chloride salt when it is used/consumed, but chlorinating liquid and bleach also add salt upon addition so accumulate salt twice as fast as other chlorine sources, but of course they don't increase CYA nor CH.

You should use winter rains to dilute the water. Since you will be closing the pool, you should be doing a partial drain anyway due to freezing conditions in your area. If you get a lot of rain or snow, then use that to dilute/refill your pool water. You should be able to do at least a 50% water replacement this way and that would cut down your salt level in half.

 

[PolareNJ]

Thanks! What is an acceptable salt level in a chlorine pool? also, we used many gallons of muriatic acid in the beginning of the season (7 or 9). Would this play a role in the salt issue?

 

[chem geek]

Yes, Muriatic Acid also adds salt. One gallon of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 22,500 gallons increases salt by 16 ppm, but 8 gallons would only be 128 ppm salt.

 

[sktn77a]

Yes, Muriatic Acid also adds salt. One gallon of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 22,500 gallons increases salt by 16 ppm, but 8 gallons would only be 128 ppm salt.

Hi: Found this thread very interesting as my CYA decreased from ~100 to ~30 over this last winter. Thankfully, I'm not having the issues that @PolareNJ had!

But I'm curious as to how adding muriatic acid (HCL and H2O) can increase sodium levels? @chem geek