What should I do if my pool chlorine is too high?

How high is too high?

Free chlorine should be 1-3 ppm in a pool and 3-5 ppm in a hot tub. A little above that is not a cause for alarm, but high chlorine can irritate eyes and skin, bleach swimwear and, over time, fade liners and damage hot tub covers and pillows.

As a rule of thumb, avoid swimming until free chlorine is back below 5 ppm, and keep out of a hot tub until it is back in its 3-5 ppm range.

Common causes

• Shocking the water - high chlorine is expected for a day or so afterwards.
• A floater or automatic feeder set too high, or left in a covered pool or hot tub.
• Adding a second dose before the first had time to show on a test.
• A cover kept on in hot weather, so the sun cannot break chlorine down.

How to bring chlorine down

The simplest method is to stop adding chlorine and let it fall naturally.

• Stop all chlorine dosing. Remove the floater or turn the feeder down.
• Take the cover off and leave the pump running. Sunlight breaks chlorine down quickly, especially if stabiliser is low.
• In a hot tub, run the jets with the lid open for an hour or two.
• Retest every 12-24 hours. Most pools come back into range within one to three days.
• If you need it down quickly, partly drain and refill with fresh water, or ask us about a chlorine neutraliser. Add any neutraliser in small amounts - it is easy to overshoot to zero.

Check your other readings with care

Very high chlorine (roughly 10 ppm and above) can bleach the other pads on a test strip, especially pH, giving a false result. Do not adjust pH or alkalinity until chlorine has dropped back below 5 ppm and you have retested.

Preventing it

Add chlorine in measured doses and give it a few hours to circulate before retesting. Start floaters on a low setting and adjust gradually. Use the app to work out doses for your water volume rather than guessing.

When to get help

If anyone has breathing difficulties, severe eye pain or a rash after using the water, get medical advice. If chlorine stays very high for days with the cover off, ask a pool professional to check your feeder or dosing system.

Frequently asked questions