How to Lower Salt in a Pool
The only way to lower salt is to drain part of the water and refill with fresh water. To bring a 15,000-gallon pool from 4,500 ppm down to 3,200 ppm, replace 29% of the water, about 4,333 gallons.
Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.
On this page (7 sections)
No chemical takes salt out of pool water, and salt doesn't evaporate. So the job is simple math: how much salty water to swap for fresh. Confirm the reading first, because a wrong reading means draining for nothing.
Calculator: percent of water to replace
Enter your salt reading, your target, the salt in your fill water (usually close to 0, but softened or well water can have some), your pool volume, and the most you want to drain at once.
With the example values (4,500 ppm now, 3,200 ppm target, fill water 0 ppm, 15,000 gallons), you replace 29% of the water: 4,333 gallons (16,403 L). At an example price of $8 per 1,000 gallons, the refill water costs about $35. Use the price on your water bill.
The formula: share to replace = (salt now − target) ÷ (salt now − salt in fill water). Pick the target from your cell's manual. Hayward's AquaRite manual, for example, lists 3,200 ppm as the best level.
Confirm the reading before you drain
- Test with a separate salt test. Use salt test strips or a salt meter for a second reading. Don't rely only on the number on the cell's control panel.
- Wait after adding salt. Hayward's manual says to run the pump for 24 hours after adding salt, and that the salt display may take 24 hours to catch up. A high reading right after a salt addition may still be settling.
- Know which number the panel shows. On the AquaRite, the main display is an average salt level. An "instant" reading is in the diagnostic menu. Other brands differ, so check your manual.
If two different tests agree that salt is high, go ahead with the calculator's number.
What high salt does to the cell
Each cell maker sets its own range, so follow the range in your manual. For the Hayward AquaRite, the manual says:
- The ideal salt level is 2,700–3,400 ppm, with 3,200 ppm best.
- A high salt level can make the AquaRite shut down. A "High Salt" light comes on when it has shut down for this reason.
- Most people start to taste salt at about 3,500–4,000 ppm.
- When the High Salt light is on, the manual says to drain some water, refill with fresh water, and repeat until salt is in range.
We could not confirm a general limit above which salt damages pool equipment, so we don't give one. If your cell has shut down, lowering salt to the maker's range is the first step. For the normal salt range and how to read it, see pool salt level.
How to lower salt, step by step
- Confirm the high reading with a second salt test.
- Enter your reading and target in the calculator above and note the gallons to replace.
- Turn off the salt cell. Drain with a submersible pump or the Waste setting on your filter valve, as your equipment manual allows. Don't drain below the lowest level your pool's manual allows.
- Refill with fresh water right away.
- Run the pump for at least a few hours to mix, then retest salt. Give the cell's display time to update before you trust it.
- If salt is still above your target, repeat with the new reading.
- Retest stabilizer (cyanuric acid, CYA), calcium, alkalinity, and pH, because fresh water changes them too.
Fresh water lowers CYA by the same share as salt, so you may need to add some back. The pool salt calculator works the other way if you overshoot. For when draining makes sense in general, see how often to drain a pool, and price the refill with the pool fill cost calculator.
Why salt ends up too high
- Salt added before the reading settled. Adding more salt because the display has not caught up yet is a common cause.
- Wrong pool volume. If your gallons are overestimated, every salt dose is too big. Check your volume with the pool volume calculator.
- Top-ups with salty water. Softened or well water can carry salt. Test it if you are not sure.
- Sodium-based chemicals. Liquid chlorine (sodium hypochlorite) turns into salt as it is used, so adding a lot of it over a season raises salt slowly. Hayward's manual describes this: chlorine turns back into salt after it works.
If the cell looks scaled, clean it as its manual says. See salt cell cleaning.
In a salt pool, salt is mostly lost through splash-out, backwashing, and rain overflow. So a pool that rarely loses water to those keeps nearly all the salt you put in. For the full care routine, see salt water pool care.
FAQ
What happens if pool salt is too high?
Many salt cells shut down and show a warning. Hayward's AquaRite turns on a High Salt light when it shuts down for this reason. The water can also start to taste salty, which the same manual puts at about 3,500–4,000 ppm.
How much water do I drain to lower salt?
Share to replace = (salt now − target) ÷ (salt now − salt in fill water). From 4,500 to 3,200 ppm, that is 29% of the water, or about 4,333 gallons in a 15,000-gallon pool.
Will rain lower the salt in my pool?
Only if the pool overflows or you drain the extra water. Rain dilutes the pool, and the salt leaves when that water leaves. Hayward's manual lists draining after rain as one of the main ways salt is lost.
Does liquid chlorine add salt to a pool?
Yes, a little. Liquid chlorine is sodium hypochlorite, and it turns into salt as it does its job. In a salt pool, a season of extra liquid chlorine can raise the salt reading slowly.
Sources
- Hayward, AquaRite owner's manual 092538 Rev D (ideal salt, High Salt shutdown, taste level, 24-hour display delay, draining is the only way to lower salt, how salt is lost): hayward.com (PDF)
- Dilution formula: methodology