Pool Staining - How To Identify The Cause
Identifying pool stains correctly is the first step toward removing them effectively. Stains vary in color, location, and texture, and are usually caused by metals, organics, or scale. Here's a simple guide to help you figure out what you're dealing with:
🔍 How to Identify Pool Stains
✅ 1. Check the Colour of the Stain
Brown/Reddish
Likely Cause - Iron
Typical Source - Bore water, rusty fittings, garden run-off
Black/ Dark Green
Likely Cause - Copper or manganese
Typical Source - Old pipes, copper-based algaecides, minerals
Blue-Green
Likely Cause - Copper or algae
Typical Source - Algaecide overdose or metal contamination
Yellow/Brown (in shady spots)
Likely Cause - Organic Matter
Typical Source - Leaves, algae, twigs, pollen
Pink or Red
Likely Cause - Bacteria (Pink slime)
Typical Source - Biofilm or poor sanitisation
White/Grey
Likely Cause - Calcium scale or residue
Typical Source - Hard water, high pH or calcium
✅ 2. Test with Household Products (Spot Tests)
🧪 Vitamin C Test (for metal stains)
Crush a Vitamin C tablet.
Rub it directly on the stain.
If it lightens or disappears, it’s likely a metal stain (iron or copper).
🧪 Chlorine Tablet Test (for organic stains)
Place a chlorine tablet on the stain (with a weight) for a few minutes.
If it fades, it’s likely organic (leaves, algae).
If it darkens, it could be a metal stain reacting to chlorine.
✅ 3. Look at the Location
Floor stains under trees = Organic
Steps, returns, or metal fixtures = Metal
Near tile lines or waterline = Scale
Corners or shady areas = Algae or organic buildup
✅ 4. Feel the Texture (if safe)
Rough, crusty or chalky = Calcium scale
Smooth, discolored but not slimy = Metal stain
Slimy or slippery = Algae or biofilm
🧠 Summary Chart:
Stain Test - Vitamin C, lightens it
Result - Metal (Iron/Copper)
Type of Stain - Metal stain
Stain Test - Chlorine fades it
Result - Organic (Leaves, algae)
Type of Stain - Organic stain
Stain Test - Chalky, doesn’t fade
Result - No effect
Type of Stain - Scale (Calcium)
If you are unsure, its best to get a professional out to assess.