Metal stains and colored water in a hot tub
Short answer
Clear green, brown or orange water and stains on the shell usually come from iron, copper or manganese in the fill water. The makers' fix is a metal sequestrant when you fill and a pre-filter on the hose.
Where do metals in hot tub water come from?
Mostly from the hose. Well water in particular can carry a lot of iron, copper and manganese, and heat plus evaporation concentrate them over time. Low pH adds its own share by corroding metal parts inside the tub.
A sequestrant doesn't remove the metal. It binds it so it stays dissolved instead of dropping out as color or a stain; Master Spas describes it that way and says to add one at every fill and on a regular basis if the bottle says so.
How do you keep metals out of a hot tub?
- Fill through an in-line pre-filter; Caldera says its own removes rust and dissolved metals as you fill.
- Add a stain and scale or metal product with each new fill, then as the label directs.
- Keep pH and alkalinity in range, so the water doesn't eat the tub's own metal.
- Never fill from a swimming pool; Caldera says pool water can damage the spa.
Green water that is cloudy rather than clear is usually algae, not metal: see green hot tub water.
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 brown?
Master Spas' troubleshooting table lists iron or manganese in the water. Add a metal sequestering agent and fill through a pre-filter next time.
What causes stains in a hot tub?
High iron or copper in the fill water, or alkalinity and pH running too low. Hot Spring's fix is to rebalance and use a metal deposit inhibitor.
Does a sequestrant remove metals from hot tub water?
No. It keeps metals dissolved so they don't stain or color the water; a water change removes them.
Sources
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