ServicesAcid Washes
Acid Washes in Guadalupe
An acid wash removes a thin skin of plaster to take stains, scale and dull gray film with it. We control the acid strength, the contact time and the rinse so your pool comes back brighter without losing more surface than the job needs.
What an acid wash does and when it makes sense
Plaster, also called marcite, is a porous mix of white cement and marble dust. Over time, metals from source water, leaves, algae and calcium settle into those pores. Brushing and chemistry stop working because the stain sits inside the surface, not on it. A diluted muriatic acid solution dissolves a very thin layer of plaster, and the stain goes with it.
That is also why an acid wash is not a routine treatment. Every wash shortens the life of the finish a little, so we only recommend one when the stain is truly set in the plaster. If a stain lifts with a vitamin C test or a targeted treatment, we tell you so and skip the wash.
Our technicians are CPO certified, so the water chemistry on both ends of the job is handled with the same care as the acid work itself.
What the acid wash includes
- 01
Stain and surface check
We test stains with spot treatments to tell metal from organic staining, and we look for delamination, hollow spots and exposed aggregate. Plaster that is already thin or flaking is not a good candidate, and we will say so before any water leaves the pool.
- 02
Controlled drain
We drain with a submersible pump and route the discharge where local rules allow. Draining is timed so the plaster does not sit empty in full afternoon sun, which dries and checks the surface.
- 03
Measured acid application
We mix muriatic acid with water at a strength matched to the stain, then work the walls and floor in small sections from the top down. Each section is scrubbed and rinsed quickly so the acid never dwells long enough to etch deeper than needed.
- 04
Neutralizing and sludge removal
The spent acid collects at the deep end as a gray slurry. We neutralize it with soda ash, pump it out and rinse the shell again so no acid residue is left in the main drain sump or along the floor.
- 05
Refill and start-up chemistry
We refill and balance pH, alkalinity and calcium hardness from the first day. Freshly exposed plaster pulls calcium from aggressive water, so getting that balance right early is what keeps the new surface smooth.
Questions about Acid Washes?
Call(480) 210-2298Signs your pool is ready for an acid wash
Stains that brushing will not move
Brown, black or green patches that stay put after scrubbing and chlorine are usually metal or organic staining inside the plaster.
An overall gray or dingy cast
When the whole finish looks dull and blotchy rather than white, a light, even acid pass usually brings the color back.
Scale on the floor and walls
Hard water leaves a rough calcium film that feels like fine sandpaper and holds dirt. Heavy scale at the waterline is a separate job, covered on our Calcium Removal and Tile Cleaning page.
Leftover staining after a green pool
Once an algae bloom is cleared, dead algae can leave dark shadows in the plaster. A wash is often the final step after Green to Clean Recovery.
How the work day runs
- 1
Walk-through and quote by phone
You describe the pool and the stains, and we set up a look at the surface. You get a free quote that explains whether a wash is the right fix and how much plaster condition limits it.
- 2
Drain and prep
We shut down and protect the equipment, drain the pool and clear debris. Lights and fittings are checked so nothing loose gets acid on it.
- 3
Wash, scrub and rinse
We work section by section with acid, brushes and a hose, rinsing each area before moving on. Stubborn spots may get a second, careful pass rather than a stronger mix across the whole pool.
- 4
Neutralize and refill
The slurry is neutralized and pumped out, the shell gets a final rinse, and refilling starts the same day. We balance the water as it fills and restart the filter and pump once levels are right.
What moves the price of an acid wash
We price each acid wash from the pool in front of us, not from a flat sheet. The quote lists each part of the job so you can see where the cost comes from. These are the things that change it most.
- Size and surface area
- More square feet of plaster means more acid, more scrubbing and more water to drain and refill.
- Stain type and depth
- A light gray film may need one pass. Deep metal stains or heavy scale can need repeat passes on specific areas, which adds labor and acid.
- Finish condition
- Thin or worn plaster takes slower, gentler work. Pools with features like spillovers, benches or tanning ledges take longer to wash evenly.
- Water and start-up chemistry
- Refill volume and the balancing chemicals needed for new source water are part of every job, and very hard fill water takes more adjustment.
Acid wash questions we hear
How often can a pool be acid washed?
Most plaster finishes handle only a few washes over their life, because each one removes a thin layer. We suggest spacing them out by several years and keeping water balanced in between. If your plaster is already rough or thin, we may point you toward resurfacing instead.
Will an acid wash damage my plaster?
Any acid wash removes some plaster, which is how it works. The difference is control: a mix matched to the stain, short contact time and a fast rinse. Done that way, the surface loses very little and stays smooth.
How long is my pool out of use?
Draining, washing and neutralizing usually happen in a single working day, with refilling running into the evening or the next day depending on size and water pressure. We balance the water as it fills, so swimming can start once chemistry is in range.
Can you acid wash a pebble or quartz finish?
Aggregate finishes can sometimes take a lighter acid treatment, but the approach is different from plaster and not every stain responds. We look at the finish first and tell you honestly what to expect.
Will the stains come back?
Metal stains return if metals keep entering the water, and scale returns if calcium and pH drift high. Steady chemistry is the best protection, which is what our Weekly Pool Cleaning service is built around.
Find out if an acid wash is the right fix
Tell us what the stains look like and how old your plaster is. We will give you a straight answer and a clear, line-item price for the work.