How to Remove Pool Stains in Los Angeles Without Draining

Stain removers are sold by color, and that is how people end up pouring the wrong one in. A brown mark can be a leaf, iron or old algae. The fix for one does nothing for the others, and chlorine poured on a metal stain can make it darker. Our acid wash page sorts the causes for a pool that is about to be drained. This page is for the step before that: finding out at home, with the water in, and treating what can be treated.

Two tests before you buy anything

Pick a stain you can reach, ideally on a step, and try these one at a time:

1. Chlorine on the spot. Drop a small amount of granular chlorine right on the stain and leave it for ten minutes, then brush. If the mark fades, it is organic: leaves, dirt or algae.
2. Vitamin C on the spot. Hold a vitamin C tablet against the stain for about a minute. If a clean circle appears under it, the stain is metal, usually iron or copper.

Nothing moved? Then it is probably not a stain in the water's sense at all. A white or gray crust is scale, and a gray, blotchy finish that ignores both tests is plaster that has aged. Skip ahead to where home methods stop. On a vinyl liner, leave the granular chlorine out: it bleaches the liner where it lands.

What the color hints at

Color is a clue, not a verdict, which is why the tests come first. Still, it narrows things down:

• Brown or tan in leaf shapes under sycamores, oaks and jacarandas: tannins from leaves left lying on the floor.
• Green or dark shadows in corners and on steps: algae, or the mark algae left behind. Raised black spots are their own problem, covered on the black algae page.
• Rust brown or orange near a fitting, a ladder or one patch of wall: iron.
• Teal, blue-green or a dark purple cast: copper, which turns plaster gray-black when there is enough of it.

Organic stains: chlorine and a brush

Leaf stains are the easy ones. Net the leaves out first, since every leaf on the floor keeps printing itself into the plaster. Then raise the chlorine to a shock level for your stabilizer reading, as the pool chemistry page explains, and brush the marks once a day. Most fade within a few days.

Autumn is when this shows up in Los Angeles, with sycamores dropping into pools across the Valley from October. A stain that has sat for months may be set into the pores. If daily brushing at shock level gets you nowhere after a week, the next step is a chlorine wash on the drained pool, which our acid wash page describes, and it removes no plaster.

Metal stains: ascorbic acid, in order

Ascorbic acid is vitamin C in bulk, sold as a pool stain treatment. It pulls the metal off the plaster and back into the water. The order matters, because the metal has to be held there afterwards or it settles right back:

1. Let the chlorine fall close to zero. Stop adding it a few days ahead. Ascorbic acid burns off chlorine, and chlorine in the water fights the treatment.
2. Turn off the salt cell or the tablet feeder, so nothing tops the chlorine back up while you work.
3. Bring pH to the low end, around 7.2. Ascorbic acid drops it further, so check again after the dose.
4. Add the ascorbic acid with the pump running, spread over the worst areas. The label gives the dose per 10,000 gallons. Brush, and give it a day.
5. Add a metal sequestrant. It binds the freed metal so it stays dissolved and goes out with the filter and backwash over the following weeks.
6. Bring chlorine back slowly, over several days. Shocking straight away knocks the metal back out of the water and onto the walls.

Then rebalance to the usual pH of 7.4 to 7.6. Saltwater pools work the same way, with the cell off until the chlorine goes back up.

Find where the metal came from

A stain you lift without finding its source comes back. Copper in Los Angeles pools has a short list of suspects. Low pH eats the copper heat exchanger inside a gas heater, and the first sign is teal on the plaster near the returns, a reason to have the heater checked. Copper algaecide and ionizers add it on purpose, so heavy use leaves its mark.

Iron is different. LA tap water carries little of it, so iron staining points to something rusting in the pool: a hairpin or screw on the floor, a corroding ladder anchor, or steel inside the shell. A rust spot that returns in the same place after treatment is reinforcement working its way out, and that is a job for rust repair, not more vitamin C.

Where home methods stop

• A white crust along the waterline is calcium scale on the tile. It comes off the tile itself, with tile cleaning.
• Gray, blotchy plaster that ignores both tests is staining set into the surface. An acid wash takes a thin layer off and evens the color, and it needs the pool empty.
• Rough plaster with the aggregate showing is a finish worn through. Washing makes it worse; the answer is resurfacing.
• Vinyl and fiberglass never get acid. Ascorbic acid in the water is fine on both.

If you do end up draining, our guide on how to drain a pool covers the ground, the sewer clean-out and the same-day refill.

What it costs

Treating it yourself means buying ascorbic acid and sequestrant, and both labels count in 10,000-gallon steps. A common LA yard pool of 20,000 gallons takes two steps of each, a big one three or four. Weekly customers see metal and stain treatments as a separate line, outside the monthly price on our price list. Plaster that needs washing is a different bill: an acid wash starts from $749, with a typical private pool between $749 and $1,250.

Not sure what you are looking at? Diagnosis is $0 inside our service area. Send a close photo of the stain with a coin for scale, or call (818) 740-6099.