One-time service
Pool Acid Wash in Los Angeles
Also called a drain and clean. Done properly it buys years of clean-looking plaster; done too often it shortens the life of the surface.
The short answer. An acid wash — also called a drain and clean — drains the pool and takes an extremely thin layer off the plaster, so the discoloured surface comes away and the clean plaster underneath becomes the surface you look at. It is the fix for a finish that has gone blotchy, stained or grey.
What it is not. It is not a repair, and it is not a routine. It will not seal a crack, stop a leak, fix water chemistry or make old plaster new — Leslie's, the pool retailer, puts the realistic result at 70–80% of the original brightness, and that is the right expectation to hold. It cannot be done on vinyl-liner or fibreglass pools at all: the acid destroys those surfaces. And every wash spends part of a finish you only get so much of. How often is safe.
Is an acid wash actually what your pool needs?
This is the part almost nobody explains, and it is the part that decides whether you spend money well. Discoloured plaster has at least six different causes, and only some of them are answered by acid. Find what you are looking at.
| What you see | Usual cause | What actually fixes it |
|---|---|---|
| Green or grey-green shadows left on the floor and walls after the water has been cleared | Algae that sat long enough to root into the pores of the plaster | Acid wash, but only after the algae itself is dead. Kill it in the water first with a green-to-clean; wash the stain afterwards if it is still there |
| Dark spots with a raised, scabby feel that grow back after brushing | Black algae, which grows down into the surface under a protective layer | Treat and brush hard first. If it keeps returning from the same spots, acid wash to open and clear the pores |
| Rust-brown or reddish streaks and blotches | Iron — from fill water, well water, or steel corroding somewhere it should not be | Usually an ascorbic acid treatment and a sequestrant, not a wash. If the source is rebar or a rusting fitting, that is a repair, and washing over it just resets the clock |
| Blue-green or teal staining, often worst near returns | Copper — commonly from a corroding heater heat exchanger or a copper-based algaecide | Find and fix the source first. An acid wash on copper staining without fixing the cause is money spent twice |
| A hard white crust along the waterline and on tile | Calcium carbonate scale from high calcium hardness and high pH | Tile-line cleaning, not a full wash. Acid lifts carbonate scale, so the waterline can often be treated on its own |
| Grey-white scale that does not fizz or soften when acid touches it | Calcium silicate — the stubborn one, built up over years | Not acid. Silicate needs mechanical removal such as bead or glass blasting. A company that acid washes this is removing your plaster and leaving the scale |
| Overall dullness, mottling, uneven grey patches, rough underfoot | Plaster age and etching, usually from years of low pH or aggressive water | An acid wash evens the colour. But if aggregate is showing through, the finish is at the end of its life and a replaster is the honest answer |
The quickest self-test: if the pool has been stagnant and you cannot see the bottom, a drain and clean is almost certainly the job. If the staining is coloured rather than green or grey, suspect metals and ask about them before anyone drains anything.
What actually happens on the day
A pool that is drained, washed and refilling again inside the same day is a pool that spent the shortest possible time at risk. That is the whole scheduling logic behind this job.
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Assess before draining
What the staining actually is, what surface it is on, and whether the ground conditions allow the pool to be emptied at all. Sustained recent rain, a hillside lot with subsurface seepage or a high water table all change the answer.
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Drain the pool
All of it, because the plaster has to be reachable. The water goes to the sanitary sewer through a clean-out, dechlorinated — in Los Angeles it does not go into the street or a storm drain.
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Mix the solution — acid into water
Roughly 50/50 acid to water. Always the acid into the water, never the reverse: the reaction is strongly exothermic, and pouring it the wrong way round can melt the container and throw acid. This is the point where doing it yourself stops being a saving.
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Pour around the edge and brush down
The mixture is applied around the perimeter and worked down the walls in sections, brushing as it goes, so it removes a very small and even layer rather than digging a pattern into the plaster. Working top-down and section by section is what stops the finish from ending up striped.
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Rinse, neutralise, pump out
The surface is rinsed and the residue neutralised before anything leaves the shell. Acidic waste is not something to send anywhere untreated.
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Refill immediately
A freshly washed surface is not left sitting dry in the sun. Filling starts as soon as the shell is clear and runs without stopping, because a pause leaves a visible ring on the new surface.
The honest limit — and why it matters
Pools are plastered with a reserve: there is at least half an inch of plaster to work with, which is why one acid wash will not break your finish. That is the reassuring half of the sentence.
Here is the other half. Every wash takes material away permanently, and it leaves the surface slightly more open and porous than it was. A more porous surface holds stains more readily, which means the next wash comes sooner than the last one. That is the trap: acid washing is a treatment that shortens the interval to its own repeat.
A workable rule. No more often than roughly every five to seven years. Over the ten to twenty years a plaster finish should last, that is about two to four washes in a lifetime — a handful, spaced years apart, each one justified. A company that offers you an acid wash every year is not selling you a clean pool. It is selling you a replaster, one year at a time.
We do this only as needed, and part of the job is telling you when it is not needed yet. If a chlorine wash will lift what you have, we will say so — it removes organic staining without removing any plaster at all.
The risk of draining, and how it is managed
Everything that makes draining dangerous in Los Angeles is a matter of timing and ground conditions, not luck.
- An empty shell can lift
Water weight holds a pool down against groundwater pressure. The mitigation is checking conditions first, avoiding the window after sustained rain, and, where the shell has one, opening the hydrostatic relief valve in the main drain.
- Plaster cracks as it dries
The mitigation is time: hours empty, not days. The wash and the refill are planned as one continuous job rather than two visits.
- Hillside access
Foothill properties often need long pump runs to reach a sewer clean-out. Worth knowing before the day, not during it.
- Weather
Nobody should be emptying a pool with rain forecast. It is the one variable that can turn a routine job into a structural one.
After the refill: the water is not finished yet
An acid wash exposes fresh plaster, and fresh plaster behaves like new plaster. For weeks afterwards the surface leaches calcium into the water and pushes pH upward, and water that is left to sort itself out during that period will either scale the new finish or etch it.
So a wash is properly followed by a start-up: daily brushing, calcium hardness held in the 200–400 ppm range, pH kept at 7.2–7.6 and alkalinity at 80–120 while the surface cures and settles. It is the same programme we run on brand-new plaster. What a plaster start-up involves.
After that, the thing that decides when you next need a wash is ordinary weekly chemistry — pH that never sits low, calcium that never sits high, and algae that never gets a fortnight to itself. What weekly service covers.
What an acid wash costs
It is quoted on the pool. The figure depends on:
- Surface area and depth
The whole interior gets worked by hand. A large deep pool is a longer day.
- How heavy the staining is
And whether one pass will do it.
- Draining and disposal
Pumping time and the distance to a sewer clean-out — the awkward part on hillside lots.
- Refill water
A full pool of metered water is a real cost and it lands on your bill, not ours.
- The start-up afterwards
Which is work, not an afterthought.
We publish the Los Angeles market rates we can verify, with sources, on our pricing page, so you can see the shape of the market before anyone quotes you. We serve 35 communities from Studio City — see the list.
Questions people ask about acid washing
How much does it cost to have a pool acid washed?
It is priced per pool rather than per square foot, because the work is mostly time: surface area and depth, how heavy the staining is, how far the drained water has to be pumped to reach a sewer clean-out, and whether a start-up follows. Refilling is a separate cost that appears on your water bill. Anyone who quotes a firm figure without seeing the pool is guessing at all four. Published Los Angeles market rates for pool work, with their sources, are on our pricing page.
When should a pool be acid washed?
When the surface itself is discoloured and the discolouration is organic or general — algae shadows left after the water has cleared, black algae rooted in the pores, or plaster that has gone blotchy and grey over years. The usual trigger is a pool that stood stagnant long enough that you could not see the bottom. It is not the answer for metal staining, for calcium silicate scale, or for a finish so worn that aggregate is showing through. As a rule of frequency: only as needed, and no more often than every five to seven years.
Is muriatic acid the same as pool acid?
Yes — muriatic acid is the trade name for diluted hydrochloric acid, and it is what is sold as pool acid. The same chemical does two very different jobs: a small measured dose lowers pH on a routine service visit, while a roughly 50/50 mix with water strips a layer off drained plaster during a wash. It is also the reason this is not a weekend project. Concentrated muriatic acid gives off fumes that damage lungs and eyes, reacts violently if water is poured into it rather than the other way round, and attacks metal fittings and equipment it is splashed onto.
Is it better to acid wash or chlorine wash a pool?
Chlorine wash first, wherever it will work. A chlorine wash scrubs a strong chlorine solution over the drained surface to bleach out organic staining — algae, leaf marks, general dinginess — and it removes no plaster at all. An acid wash removes material, so it is the stronger and more costly option in every sense. If your problem is organic and recent, ask for a chlorine wash. If the staining is set into the pores, or the plaster itself has discoloured, acid is what will move it.
Can a pool be acid washed without draining it?
There is a technique marketed as a no-drain acid wash, where acid is added to the full pool to dissolve scale and lift light staining. It has a real use — descaling — and it avoids the risk of emptying the shell. But it is not the same job: it will not remove a layer of discoloured plaster, so it does not restore a blotched finish to one colour, and it puts the whole body of water into an aggressive state that must be corrected afterwards. If your surface is stained rather than scaled, it will not do what you are hoping for.
Will an acid wash damage my plaster?
One properly done wash will not. Pools are plastered with at least half an inch of reserve, and the layer removed is very thin. The damage is cumulative rather than immediate: each wash takes material permanently and leaves the surface a little more porous, so it stains faster and the next wash arrives sooner. A handful over the life of a finish is normal. An annual acid wash is how a twenty-year plaster job becomes a ten-year one. And on vinyl-liner or fibreglass pools it is not a question of damage but of destruction — those surfaces must never be acid washed.
Send us a photo before you commit to anything
Most of the diagnosis above can be made from a clear picture of the stained area and a calcium hardness reading. Sometimes the answer is an acid wash. Sometimes it is a green-to-clean, a stain treatment, a tile-line clean or an equipment repair — and those are cheaper conversations we would rather have first.