Why is my hot tub water green?
Short answer
Cloudy green water points to algae and low sanitizer; clear green water points to dissolved copper or iron. Master Spas' manual says shock and restore sanitizer for the first and add a metal sequestrant for the second.
Is green hot tub water algae or metal?
Look through it. Algae clouds the water; metal tints water that is otherwise clear. Master Spas' table splits them exactly that way. For the metal kind, see hot tub stains and metals.
How do you fix green, cloudy hot tub water?
- Test alkalinity and pH and bring them into range; Hot Spring ties algae to high pH.
- Shock with sanitizer and keep the level up afterward.
- Clean the filter, since it holds what you just killed.
- If it is visible or keeps coming back, drain, clean and refill.
Growth that returns after a fresh fill can live in the plumbing; see biofilm and line flushing.
How much to add
The product label sets the dose, by your tub's gallons.
Strengths differ between brands of the same chemical, so we don't print amounts. Test, read the label, add a little at a time with the jets running, wait, and test again. Your tub's gallons are in its manual or in our gallons and filter size table.
Common questions
Why is my hot tub water green but clear?
Usually copper or iron from the fill water. Master Spas' fix is a metal sequestering agent.
Can you use a hot tub with green water?
Not until you know why. Cloudy green water means sanitizer has fallen behind; fix the chemistry and shock first.
How do you get rid of algae in a hot tub?
Balance pH, shock with sanitizer and keep the level up, and clean the filter. If it is visible or persistent, Hot Spring says drain, clean and refill.
Sources
2
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