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My “Check Salt” Light Will Not Go Out

I keep adding salt to my pool, but it keeps telling me to add more.

There is a dirty little secret behind the “add salt” indicator. Most salt systems do not actually measure the salt level in the pool. They only guess at it based on the current draw of the cell. If you don’t understand this, you can get the salt level way too high in your pool.This is why you should ALWAYS verify your salt level with a test kit or meter before adding salt to your pool.

There are four possible scenarios in which the “add salt” light can go on:

  1. The water is really cold
  2. The cell is worn out
  3. The salt level is actually low
  4. The “add salt/check cell” light automatically comes on every 500 hours (Hayward)

Most saltwater chlorinators (except for Jandy AquaPure) do not actually measure the salt level of the pool water. Instead they monitor the amp draw of the salt cell and extrapolate a salt reading off of that amp draw. Here is the logic behind this:

  • More salt in the water makes the water more electrically conductive
  • More conductive water will draw more amperage across the cell plates

THEREFORE:The salt level in the water directly correlates to the amp draw. Here is the flaw in this logic . . . there are some other things that can cause a low amperage reading.

  • A bad cell – will not conduct much electrical current across the cell.
  • Cold water – will also not be as conductive.
  • A little timer inside the system that turns the “check salt” light on every 500 hours

ALWAYS HAVE YOUR WATER TESTED MANUALLY BEFORE ADDING SALT. We could tell you a bunch of stories about people who got the salt level in their pool above 5000 ppm because they kept adding salt when they did not need it, and then they had to drain a bunch of water out of their pool to keep the high salt level from damaging their equipment.

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