Domakihub How to Remove Pool Stains and Keep Your Pool Looking New
Identify the stain type, apply the right treatment, and stop it coming back.
Reviewed by Domakihub pool pros · 2026-06-23 · 5 min read
Pool stains are one of the most common complaints from home owners, holiday rental managers, and hotel operators across Greece, where long sun seasons, mineral-rich water, and high bather loads create ideal conditions for discolouration. The video above walks through the diagnosis and treatment visually; this guide gives you the step-by-step process so you can tackle any stain with the right product the first time. Get the identification right and you will save both chemicals and effort.
Why Pools Stain: The Two Main Culprits
Pool stains fall into two broad families: organic stains from leaves, algae, insects, and sunscreen; and metal stains from iron, copper, and manganese dissolved in fill water or released by corroding fittings. Organic stains are usually brown or green and appear near skimmers or on steps where debris settles. Metal stains range from rust-orange (iron) to blue-green (copper) and to black-purple (manganese), and they are especially common in areas of Greece where well water or borehole water is used to fill the pool.
The treatment for each family is completely different. Chlorine breaks down organic matter but can actually fix metal stains permanently into the plaster if applied before the metals are sequestered. Knowing which type you are dealing with before reaching for any chemical is the single most important step in the whole process.
Stain Identification: The Quick Field Test
Before buying anything, do a simple spot test. Press a small amount of dry granular chlorine onto an organic stain and hold it there for 30 seconds with a pole brush; if the stain lightens or disappears, it is organic. For a suspected metal stain, press a vitamin C tablet (ascorbic acid) against the surface instead; if that lightens it, you are dealing with metals — typically iron or copper. This two-minute test prevents the most common and costly mistake pool owners make: dosing the wrong chemical family and locking the stain in permanently.
If neither test produces a clear result, check your source water with a metals test kit. Greek coastal properties on island water supplies and mainland properties using borehole water frequently show elevated iron and manganese, so a metals test is always worthwhile when diagnosing a new stain.
How to Remove Pool Stains: 5 Steps
- 1
Balance the water chemistry first
Test and adjust pH to 7.2–7.4 and alkalinity to 80–120 ppm before adding any stain treatment. Off-spec water reduces the effectiveness of every chemical you apply and can cause new problems. For metal stains, also drop the free chlorine to below 1 ppm before proceeding, because chlorine oxidises metals and bonds them to the surface.
- 2
Identify the stain type with a spot test
Use the granular chlorine test for suspected organic stains and the vitamin C (ascorbic acid) test for suspected metal stains. Run the appropriate test on the most prominent stain and note the result before buying any treatment product. If both tests are inconclusive, send a water sample to a pool lab — several pool-supply shops in Athens and Thessaloniki offer this service.
- 3
Apply the correct treatment chemical
For organic stains, shock the pool to 10 ppm chlorine with calcium hypochlorite or liquid chlorine, brush the stained surfaces vigorously, and run the filter continuously for 24 hours. For metal stains, add an ascorbic acid stain treatment (follow the manufacturer's dose per cubic metre of water) distributed evenly around the pool, then brush the stains — they should fade within one to four hours. For stubborn copper stains, a specialist sequestering agent designed for copper is more reliable than ascorbic acid alone.
- 4
Run the filter and vacuum to waste
After treatment, run the filter continuously for at least 24 hours to clear the loosened material and any chemical residue. For organic stains that produced heavy debris, vacuum to waste rather than through the filter to avoid clogging the media. For metal stain treatment, keep the pump running to fully circulate the sequestering or ascorbic acid solution. Check and re-balance pH and alkalinity at the 24-hour mark, as both acid and shock treatments shift water chemistry significantly.
- 5
Prevent recurrence with ongoing maintenance
For organic stains, keep chlorine consistently in the 1–3 ppm range, skim debris daily, and brush walls weekly. For metal stains, add a sequestering (chelating) agent monthly, especially if the pool is refilled with mineral-heavy source water. Test for metals twice per season and at every major refill. Inspect copper fittings, heat-exchanger manifolds, and sacrificial anodes annually — corroding equipment is the most common source of copper in Greek residential pools.
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FAQ
- Can I remove pool stains without draining the water?
- Yes, in most cases. Organic stains respond to shock treatment while the pool is full and in use. Metal stains can be treated with ascorbic acid or specialist sequestering products without draining, though you will need to drop chlorine levels beforehand. Draining is rarely necessary and is generally not recommended for plastered pools in warm climates, as empty plaster can crack under direct sun.
- My pool has a persistent blue-green stain near the return jets — what is it?
- Blue-green staining near return jets is almost always copper. The most common causes are a copper-based algaecide, a corroding heat exchanger or copper pipe, or naturally high copper levels in the fill water. Treat with an ascorbic acid wash followed by a long-term sequestering agent, then identify and fix the copper source — otherwise the stain will return within weeks.
- How often should I check my pool water for metals in Greece?
- At minimum twice per swimming season: once at opening and once mid-season. If you use borehole or well water to top up the pool, test for metals every time you add a significant volume of water. Greek well water in many regions contains elevated iron and manganese, so proactive testing is far cheaper than treating a deep-set metallic stain.