By The Zagosa Team. Published .
Reviewed or updated .
Green, hazy water usually points to algae taking hold after the sanitiser level fell too low. You need to correct the balance, shock the water, keep it filtering and collect the remaining fine debris. Stay out of the tub until the water is clear and your test shows free chlorine at 3 to 5 ppm or total bromine at 4 to 6 ppm.
Why green and cloudy water develops
A green tint can sometimes come from metals in fresh water, while cloudiness alone often comes from particles that pass through the filter. When both appear together, algae is the more likely cause. A low sanitiser reading gives growth time to start, then algae and organic debris make the water murky.
Think back over the previous few days. Heavy use, missed treatment or a cartridge left dirty for several weeks can quickly overload the water, particularly during warm weather.
Clear green water step by step
- Take out the cartridge and rinse it thoroughly. Replace it if the pleats are damaged or no longer clean properly.
- Test the water, then adjust pH to 7.2 to 7.6 and total alkalinity to 80 to 120 ppm. Shock treatment is less effective when the balance is wrong.
- Apply the shock amount stated on its label, rather than a normal maintenance top-up. Add it with circulation running and leave the cover open. If you use Non-Chlorine Shock, pre-dissolve 17 g per 1,000 L, circulate uncovered for 15 to 30 minutes and wait at least 15 minutes before testing.
- Leave filtration running continuously for 24 hours. As the green colour disappears, the water may become a grey haze. Rinse the cartridge again so trapped material does not restrict its flow.
- If haze remains, add 50 ml of Sparkle Clarifier per 1,500 L. It gathers tiny particles into larger groups that the cartridge can retain. Allow another one or two days for filtration to finish clearing the water.
When draining is the better option
Choose a drain and refill if the problem has lasted more than a week, the seats are hidden by the cloudiness or an earthy odour remains after treatment. Before draining, clean the hidden plumbing with Hot Tub Flush so residue in the pipes does not contaminate the replacement water.
Questions about green hot tub water
Should I use a green hot tub?
No. A visible water problem means you cannot confirm that treatment is under control. Wait until you can see clearly through the water and testing confirms free chlorine at 3 to 5 ppm or total bromine at 4 to 6 ppm.
How soon can I use it again?
Clearing a badly affected tub commonly takes two or three days from the first shock treatment. The deciding checks are clear water, sanitiser within its correct band and no strong chemical odour, not the time alone.
Why does green water seem to appear quickly?
The change may look sudden, but algae will normally have been developing unnoticed for several days. Once sanitiser is exhausted, warm water can let the visible colour intensify quickly.