Salt in a Non-SWCG Pool

[mbooker228]

Moderator note - Moved from here: Cost Comparison of Chlorine Sources


Hi,

great posts chem geek.

I am struggling to find what the effect of high salt levels in an indoor pool which does not have a salt water chlorinator is. Please point me to a relevant post.

Thanks

 

[tim5055]

Welcome to TFP!

I would have a couple of questions-

What is the source of the salt you are concerned about?

Can you give a description of the pool and equipment installed.

I can tell you that many people add salt to a non-SWCG pool because they like the feel of the water. Even with a SWCG pool the amount of salt in the water is very low. People seem to equate a SWCG pool to ocean water, but the salt level is no where near that concentrated. Many can't even taste the salt in the water.

 

[woodyp]

About 1 tenth as salty as the ocean on average.

 

[chem geek]

An indoor pool usually has a lower daily chlorine usage than an outdoor pool since there is no exposure to sunlight. So usually the salt buildup is slower as a result. On the other hand, one does not get dilution from rain overflow so one needs to intentionally dilute the water unless they are regularly doing so with backwashing.

At 1 ppm FC per day chlorine usage (and your usage may be lower than that), using chlorinating liquid or bleach has the salt build up by around 50 ppm per month. So even if maintained year-round, that's 600 ppm per year. It would take 3 years to get 1800 ppm higher and that's still less than the 3000 ppm used in saltwater chlorine generators. What exactly is your concern?

 

[Ronald U.]

Going off of what chem geek just said, after 3 -6 years of slowly, unintentionally salting a non-SWG outdoor pool, is there any concern for the salt levels that may approach several thousand ppm? I have always seen the salt increase calculated by the PoolMath "what is the effect of adding..." calculator at bottom of PoolMath page, and wondered if it ever becomes an issue in a pool that is never drained to any significant extent. Thanks.

 

[chem geek]

Significantly higher salt levels increase metal corrosion rates. So if the pool doesn't have higher grade stainless steel (316/316L instead of 304) or has aluminum in the water (such as some automatic electric covers) or has a copper heat exchanger in a gas heater, then these can corrode faster at higher salt levels. If you have soft stone then salt splash-out with evaporation can create salt recrystallization pressure to crack the stone. Basically, it's the same types of problems that can happen in SWG pools and these issues can be mitigated in the same ways.

 

[Ronald U.]

I have no metal. However, should I check salt level every couple of years?

 

[chem geek]

Sure. Certainly it's not necessary to check more than once per year.