Bleach, Salt, and TDS

[SPP]

Hello Richard,

If my 12% bleach results only is salt residue, does this means I will get higher TDS over time ?
I have not been using my TDS meter for a long time.

Thanks
SPP

 

[JasonLion]

Every chemical you add to a pool will increase the TDS. This is true of bleach, trichlor, cal-hypo, baking soda, CYA, salt, everything. Likewise, all forms of chlorine end up adding some salt to the water. Bleach adds a little more salt than other forms of chlorine, but the difference is not normally significant.

TDS is not an important measure of water quality. The TDS level can be quite high and make almost no difference. There are a few particular chemicals that will cause problems sometimes, like CYA, but much better to test for them in particular and ignore TDS.

 

[SPP]

Thanks Jason.
I forgot where I read that a pool water is to be retired/changed after 1,500 PPM TDS or so or else problems will occur.

That sounds like impossible for salt water generator pool... where the salt will be measured as TDS too ( right ? )and easily 3,000 to 4,000 TDS to be able for the cell to operate properly.

Assuming high TDS does effect pool water quality for non salt pool, what level is a documented one ?

Regards,
SPP

 

[Guest]

Like Jason said it's not the TDS per se but what it is comprised of that matters.
When stabilized chlorine came into general use it was found that TDS roughly correlated with the CYA levels in the water and all the negatives that were attributed to high TDS were actually from the high CYA. If the high TDS is from salt, as you noted, it has no adverse effects. It is better to monitor the actual components of TDS (CYA, CH, etc.) than worry about TDS.

 

[SPP]

Thanks WB,

Indeed anything that "join" the water is TDS.
Some 6 months ago I got 500 something TDS, today its 859, hope my meter is accurate.
My city water is 300 something TDS, but my pool was from tankers...never measured the TDS then, I do not have the meter yet...

So that's why people been saying 1500 TDS as maximum...its CYA related... :lol:
I have CYA at approx 25ppm. I have CH at 160 PPM. I been adding some other chemicals this year.

Ok, one more good info from the seniors...thanks guys.

 

[chem geek]

Ditto to what others have said. TDS as a single measurement isn't very useful -- it's what TDS is composed of that matters.

All sources of chlorine will have 10 ppm FC convert to 8 ppm salt from chlorine converting to chloride. Chlorinating liquid, bleach and lithium hypochlorite add an additional 8 ppm salt (for every 10 ppm FC) upon initial addition. Cal-Hypo adds less extra salt (chloride) of around 2 ppm but also adds 7 ppm to CH. Trichlor, Dichlor and chlorine gas add no extra salt but of course Trichlor adds 6 ppm to CYA and Dichlor adds 9 ppm to CYA. Salt, CH and CYA will get measured as TDS, though a TDS meter will only measure charged ions (it measures conductivity) and not neutral species, but the dominant form of CYA in the water is charged (cyanurate ion).

About the only use for TDS that I can see is as a proxy for how "old" the water is based on the amount of rise in TDS. That can approximate the amount of other unmeasured chemicals, such as unoxidized organics, that might be in the pool. Even then, I wouldn't just change the water because it's old; I'd see if there are problems with a dull appearance or cloudiness or unexplained chlorine demand that aren't resolved by any other means.

 

[SPP]

Thanks Richard...
I am getting to know the pool actual chemistry better ....slowly.
On average residential pool in my country gets its water change every 2 years if not 1 year.
Somehow they believe that the water gets "old or tired" by then.

Now I realized that they either been CYA over dosed or CH over dosed over time.
Even my friend who sells pool equipment and build pools, he doesn't know to what extend CYA can cause trouble, if too much of it. They call it chlorine with stabilizer, that's it may it be Tri or Di.... and better since it "last longer" and more expensive too.... than the cal 65%

Its here in the forum that I get answer to the level I really need...
Thanks guys, you all are fountains of info wealth...