Water, clarity and algae
Metal stains in a pool
Brown or reddish marks often mean iron; blue-green marks often mean copper. Both come out of the water and onto the surface.
Metals dissolved in pool water can come from top-up water, from corroding heater exchangers, pipes and fittings, or from some algaecides. When pH rises or the water is shocked, these metals can drop out of solution and settle on the floor and walls as stains, or colour the water itself.
Water guides explain what a reading or a symptom means and the order in which to correct it.
Telling metal stains from organic stains is the first step. A small amount of a vitamin C based stain remover held against the mark usually lifts metal stains; organic stains respond to chlorine instead. Once the type is known, the stain can be lifted and the metal kept in solution so it does not return.
The short version
Identify the stain type
Metal and organic stains need different treatments.
Find the metal source
Corroding equipment keeps adding metal until it is addressed.
Keep metals in solution
Sequestering agents stop metals settling out again.
How metal stains are treated
Spot testing
A small amount of stain remover against the mark shows whether it is metal.
Lifting stains
An acid-based stain treatment is circulated with careful balancing afterwards.
Preventing return
Balanced pH and a sequestrant keep remaining metals dissolved.
Before treating stains
Check equipment for corrosion
Heaters, ladders and pipework can be the source.
Test the top-up water
Some water sources carry iron.
Avoid shocking first
Shocking metal-rich water can make stains worse.
Common questions
Why did my pool turn green-brown after shock?
Metals in the water can oxidise when shocked, changing the water colour.
Will stains come back?
They can if the metal source remains. Treating the source and using a sequestrant helps.
Can stains damage the pool?
They are mostly cosmetic, but the corrosion behind them can damage equipment.
Related pool care guides
- Organic stains in a poolAnother water problem with a related cause.
- Foam on pool waterAnother water problem with a related cause.
- Dealing with a contamination incident in a private poolPool care for a related situation.
- Liquid chlorine or chlorine tabletsA related choice about how the pool is looked after.
This guide sits under pool water treatment. Browse all pool care guides. We look after pools at homes and commercial properties across Dubai.
Ask about your pool
A clear photograph and your latest test reading are usually enough for a useful first answer.
Phone
+971 56 181 0106Talk through what the pool is doing and book a time for us to see it.
WhatsApp
Send a messageThe easiest way to send photographs of the pool and plant room.
Next step
Send us a photo of the stain
A clear photograph and a note of recent dosing help us tell what kind of stain it is and how to treat it.