How much will salt concentration increase due to liquid chlorine?

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C

Chaddy

0
Aug 21, 2013
25
Austin, Texas
Here are my current numbers.

FC 4
pH 7.5
TA 70
CH 460
CYA 50
Salt ???
Borate 50


I have been using TFP methods since August of 2013 and have been very pleased. I use a Liquidator and added Borates to help with the white scale issues that popped up immediately. Borates fixed that problem. My question has to do with the accumulation of salt concentration over time. Here's a list of facts associated with my situation.

1. We had a good deal of rain this past winter/spring to the extent that my CYA was very low. I tested at about 10ppm and took a sample to Leslie's to confirm. They tested at 20. However, they also reported TDS at 4500. I'm guessing the TDS number has quite a bit of salt in it, but I don't know how much.

2. I can notice a salty taste to my water.

3. I am noticing some degradation of some rock surfaces around my pool.

I know this post may be premature and I need to get a salt concentration test done, but I was wondering if anyone else has seen marked increases in salt concentration due to liquid chlorine use. I have a cartridge filter so I don't get any dilution due to backwashing. However, if my salt is high now, it was probably even higher before all of the rain diluted everything (my CH went from about 550 down to 450-460 from the rain).

I plan to seal the stone around my pool this winter, but I am also wondering if a switch to a generator is warranted. I'd rather not have to drain half my pool in order to deal with increasing salt levels.
 
Thanks for the links. I had already read through those before I posted this. Just to update the salt is 3000-3500 (3000 from a drop test and 3500 from a strip). So, unlike other's experiences I seem to be accumulating about 1000 ppm of salt per year. Does that even seem reasonable? I'm not sure what to make of that. Do I drain half the pool per year or two or do I switch to a salt generator?
 
If you use PoolMath, then here's some numbers -

For every 10 gallons (1280oz) of 10% LC added, you increase salt concentration by 132ppm.

So to go from 0 to 3000ppm you would have had to add 227 gallons of 10% LC.

Do you think you have used that much bleach since starting TFP?


Sent from my iPhone using Tapatalk
 
Last edited:
Sure. That's not out of the realm of possibilities. About ~3 gallons a week average during April-September, and ~1 per week average during the other times would be about 100 gallons per year. That may be a bit high of an estimate but certainly possible. But I have also had some dilution due to splash out and rain overflow.

However, the simplest explanation is probably the right one.

Does baking soda add some salt content as well?

Thanks for your input.
 
Chaddy said:
Sure. That's not out of the realm of possibilities. About ~3 gallons a week average during April-September, and ~1 per week average during the other times would be about 100 gallons per year. That may be a bit high of an estimate but certainly possible. But I have also had some dilution due to splash out and rain overflow.

However, the simplest explanation is probably the right one.

Does baking soda add some salt content as well?

Thanks for your input.
Click to expand...

Yes. The baking soda is sodium bicarbonate. The bicarbonate ion consumes hydrogen (causing the pH to rise) as CO2 outgasses from the pool water. The other half of that reaction (which can basically be ignored) is that the sodium ion is balanced by the chloride ion from the muriatic acid.

So yes, baking soda eventually becomes CO2 and salt. In fact, lots of reactions in the pool eventually become salt. The addition of borax essentially consumes acid and results in borate anions and salt. Chlorine reactions eventually result in chlorine converting into chloride (a salt water generator reverses that process turning chloride back into chlorine). And on, and on, and on it goes......
 
I just entered in 3500 for the salt concentration into the PoolMath page and saw that this reduces the CSI by about 0.2. Do you think that by raising the CSI closer to zero or even positive, it could help with the problems I am seeing with my stone?
 
I have been TFP from day one of March, 2014. Last week I measured my salt level for the first time using strips and it's 3400. Seeing as how I have high Calcium anyway from the initial fill, and high pH from water feature aeration, the salt level actually helps my csi index quite a bit, to prevent scaling.
 
Chaddy said:
I just entered in 3500 for the salt concentration into the PoolMath page and saw that this reduces the CSI by about 0.2. Do you think that by raising the CSI closer to zero or even positive, it could help with the problems I am seeing with my stone?
Click to expand...

If you are talking about stone outside the pool not immersed in the pool water, then no the CSI of the pool water won't help with the stone. Splash-out and evaporation leaves salt behind and when it dries it crystallizes creating tremendous pressure that cracks/chips/flakes stone and concrete. Sealing the stone is the best way to protect it. Frequent washing/diluting with water is another way and happens naturally in areas of the country that get frequent summer rains which is why you don't see salt/stone problems in places like Florida, but do in Texas and Arizona. What you are experiencing is the same thing that some with SWG pools experience since their salt levels are around 3000 ppm.

2 ppm FC per day of chlorinating liquid or bleach will increase salt levels by about 100 ppm per month. If you add acid and baking soda over time, then that adds additional salt. Note that ALL sources of chlorine will add salt because when chlorine is used/consumed it results in chloride salt, but other sources of chlorine add about half as much salt but of course add other things. With stabilized chlorine (Trichlor, Dichlor) you get half the sodium chloride salt (including the base you need to add to maintain pH), but with Trichlor that same 2 ppm FC per day results in 36 ppm CYA per month and with Dichlor it's 54 ppm CYA per month. With Cal-Hypo one gets less salt (not quite half), but that same 2 ppm FC per day results in 42 ppm CH per month.
 

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