Pool Stains in Sanur: What They Are and How to Fix Them

Stains on the pool bottom or walls are almost always one of three things: organic residue such as leaves, sunscreen, or bird droppings; dissolved metals leaching from old pipes and fittings; or algae that has rooted into the plaster. In Sanur's salty, humid air, combined with PDAM water that can carry iron and manganese, these spots appear faster than you would expect back home. The good news is that most of them come off with the right product applied correctly — a full acid wash is rarely necessary.

Organic Stains: Leaves, Sunscreen, Bird Droppings

The most common culprit in a Sanur villa pool is simple organic matter. A single mango leaf left floating for two days will leave a brown ring on the tile. Sunscreen and body oils build up around the shallow end where people sit. And the frigate birds that roost along the coast drop their mess directly onto uncovered pools.

During the rainy season (roughly November to March) the problem multiplies. Wind-driven rain stirs up dust, pollen, and tiny plant fragments that settle on the pool floor overnight. If the filter runs only six hours a day, those particles have time to bond with the surface before they are caught.

• Brown or tan rings: usually a leaf, coffee stain, or bird droppings that sat too long.
• Faint yellowish film across the whole floor: sunscreen and body oils accumulating between cleanings.
• Dark speckled patches near the skimmer: trapped debris that was never vacuumed out.

Metal Stains: Iron, Copper, Manganese

Many older villas in Sanur were wired with galvanized steel plumbing or copper fittings that are now slowly corroding. When PDAM water — which can carry trace iron and manganese depending on the district — passes through these pipes, it deposits coloured stains wherever the flow is slowest: around ladders, at the drain cover, along the tile line, and on the deep end where circulation is weakest.

Iron stains look orange-brown, like dried rust. Copper stains appear blue-green or even black. Manganese gives a dark grey-black ring. A quick test: wipe the spot with a cotton pad soaked in white vinegar. If the colour transfers to the pad, you are dealing with a metal deposit rather than algae or organic matter.

• Orange-brown rings around the ladder or return jet: iron from old pipe work.
• Blue-green or black spots near the main drain: copper or manganese leaching from fittings.
• If the stain reappears within two weeks of cleaning, the source (a corroded fitting or a section of pipe) needs to be replaced, not just cleaned.

Algae That Has Rooted Into the Surface

Floating algae you can vacuum out are one thing. Algae that has been sitting for several days starts producing a slimy biofilm that grips the plaster. Once it roots, brushing alone will not lift it — you need a targeted algaecide treatment followed by mechanical scrubbing.

Sanur's humidity and warm water temperatures mean algae cycles run faster here than in cooler climates. Black algae in particular loves small cracks or rough patches in older pool surfaces. It looks like tiny dark dots that seem to multiply no matter how much chlorine you add.

• Green slime: the most common type; usually responds to a shock dose plus vigorous brushing.
• Mustard (yellow-green) algae: often resistant to standard chlorine; needs a phosphate remover and a dedicated algaecide.
• Black algae: rooted deep in micro-cracks; requires a concentrated black-algae product applied directly with a brush, left 30 minutes, then rinsed.

How to Remove Pool Stains Step by Step

Step one is always identification. Do not reach for acid before you know what you are dealing with. The vinegar-patch test above takes two minutes and saves you from etching tile unnecessarily.

For organic stains: drain the water level just below the stain if it is on the wall, apply a mild alkaline cleaner or a dedicated organic-stain remover, scrub with a nylon brush, let it sit 15–20 minutes, then rinse thoroughly with the return jet. Repeat once if needed.

For metal stains: use an iron-remover or sequestrant product specifically labelled for pools. Apply to the dry spot, wait the time stated on the label, then scrub and rinse. If the source pipe is still corroding, plan to have that section replaced — otherwise the stain will come back within weeks.

For rooted algae: shock the pool first (follow the product's dosage chart), then apply a targeted algaecide directly onto the stained area, scrub firmly with a stiff-bristle brush, leave 30 minutes, and vacuum to waste so the dead algae does not settle back down.

• Never mix chlorine-based products with acids or ammonia. Fumes can be dangerous in a small villa courtyard. If you smell strong chemical fumes, ventilate immediately and stop working.
• Wear rubber gloves and eye protection when handling concentrated removers, especially around children who may be nearby in the garden.
• If the stain covers more than a square metre, or if you are unsure of the type, send a photo before buying chemicals — the wrong product can etch tile or damage plaster.

Preventing Stains From Coming Back

The single most effective habit is daily skimming plus a weekly brushing of the walls and floor. Five minutes with a soft brush keeps biofilm from bonding and stops algae from getting a foothold.

Run your filter for at least eight hours a day, and extend that during the rainy season when organic load spikes. Check the sand or cartridge every two weeks; a clogged filter lets fine particles recirculate onto the surface.

Test your water twice a week: free chlorine (1–3 ppm), pH (7.2–7.6), alkalinity (80–120 ppm). In Sanur's heat, chlorine drops faster, so do not rely on a monthly check.

Cover the pool overnight or during heavy rain to keep leaves and bird droppings out. A simple fitted cover costs less than one visit to remove a month's worth of organic staining.

If your villa is older and you notice rust-coloured water after the PDAM supply has been off for a few days, ask about flushing the line or installing an inline sequestrant doser before the water reaches the pool.

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