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.