When to Add Salt to a Swimming Pool

Here are some reasons why you should add salt:

Digital meter shows salt level under 3000 ppm

The water temperature is over 60 degrees F

The pool surface is over 60 days old (new build or remodel plaster pool)

The saltwater cell is clean and functioning

You have a saltwater generator on your equipment

Here are some reasons why you should not add salt:

You do not have a saltwater generator attached to your pool equipment

The salt cell is dirty

The system is showing low salt – built-in salinity monitor

The pool plaster is fresh, under 2 months old

The water temperature is below 60 degrees

If you follow this basic rule you will have little issues with adding salt to a pool when it is not needed.

If the salt cell is dirty the system can give you a false low salt indication. It is because the calcium on the plates reduces the electrical current and the system may think the salinity (salt level) is low, when in fact it is not. Cleaning the salt cell will reset the system in most cases and the proper salinity reading will appear on the display after a few hours or the next day.

Using a digital salinity meter is a must. Get a good one and the more you pay the better quality the meter will be. I have several videos on them and the  LaMotte, Hach, and Oakton models are the top 3 in my book. I trust the digital meter readings over the system reading and will never add salt without first getting my separate independent reading. 

I understand that the pool builder has a two-week close-out when the pool is finished. They are not really in a rush to add salt but since they are handing the pool off they want everything to be done. So many will add salt in the first 2 weeks of the fill. In my experience waiting 30-60 days is a better idea and will eliminate issues with plaster staining and very high uncontrollable pH. As the plaster cures, there is already a high acid demand, and with the saltwater generator also raising the pH it will be hard to prevent scale from forming as the plaster cures. Not as bad as a problem in a PebbleTec, Vinyl, or Fiberglass pool but for plaster, I would wait at least 60 days before adding salt.

Some reasons why the salt cell may not be producing chlorine are that it is too small or not rated for that pool size or the CYA level is too low. It may not be a low salt level causing the issue. Also, low water temperatures under 60 degrees F in most cases will cause the salt system to stop producing.

Each SWG has different salt cell sizes. For example, the Intellichor 40 and Hayward T-Cell 15 are rated for a pool of up to 40,000 gallons. The Ichlor 30 and Jandy TruClear are rated for pools up to 30,000. The Intellichlor IC20 is for a pool of up to 20,000 gallons. Your salt cell should be rated for your pool size to be effective. If you put an IC20 in a 25,000-gallon pool it will need to run 24/7 just to be partially effective. An IC40 in a 15,000-gallon pool would be ideal with plenty of margins.

Like any other form of chlorine, the SWG is producing chlorine that needs to be protected from the harsh UV rays of the sun. Ideally, your CYA level should be 30-50 ppm but if you notice the chlorine level is still not holding you can increase the CYA to 80 ppm. If the CYA is below 30 ppm chances are your SWG will be producing chlorine at a rate that is less than the burn-off from the UV rays. Check to make sure the CYA is at alt least 30 ppm.

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