Draining, cleaning and acid washing is the lowest-cost way to refresh a pool whose plaster is still sound but looks tired. We drain the pool, scrub away dirt and algae, wash the plaster with a diluted acid solution to strip stains and scale, neutralize, rinse and refill. On the right pool, it can buy a few more good-looking seasons before a full resurface.
We'll also tell you when an acid wash is the wrong move, because on thin or rough plaster it speeds up the end. Send a few photos for a free estimate and we'll give you a straight answer.
Signs your pool needs a drain and acid wash
An acid wash makes sense when the surface is stained, not damaged. Good candidates show:
- Overall dinginess or gray cast. Plaster that looks dull even with clear water.
- Algae staining. Green or black stains left after an algae bloom or a pool that sat neglected.
- Leaf and organic stains. Brown or tan marks from leaves and debris left on the floor through the winter.
- Light scale. Thin white calcium buildup from Denver's hard water, especially on steps and at the waterline.
- Total dissolved solids (TDS) are high. Water that has been topped up for years can carry so many dissolved minerals that chemistry is hard to keep in balance. A drain and refill resets it.
- A pool that's been closed for a long time. Many owners with an inherited or neglected pool start here.
Not a good candidate: plaster that's rough, thin, hollow, flaking or worn through to gray shell. For those pools, see replastering or crack and hollow-spot repair.
Before you drain: groundwater and hydrostatic pressure
Draining is the riskiest part of any pool job if it's done without checking conditions first. An in-ground pool sits in the soil like a boat. When it's full, the weight of the water holds it down. When it's empty, groundwater under and around the shell pushes up, and if that pressure is high enough it can crack the floor or even lift the whole pool out of the ground.
Here's how we manage that risk:
- We check the ground first. After heavy rain or snowmelt, or on lots near creeks, ponds or low ground, the water table can sit close to the pool floor. We'll postpone draining if conditions look wrong.
- We confirm the hydrostatic relief valve. Most in-ground pools have a relief valve in or near the main drain that lets groundwater in before it can push the shell up. We check it and open it when draining.
- We keep the pool empty for as short a time as possible. Acid washes are usually drained, washed and refilling within 1–2 days.
- We route water legally. Many Front Range cities don't allow chlorinated pool water in storm drains. We dechlorinate and discharge where your city permits, typically to a sanitary sewer cleanout.
If you're thinking of draining the pool yourself, please call first. A lifted or cracked shell costs far more than an acid wash.
Our drain, clean and acid wash process
A standard residential drain, clean and acid wash takes 1–2 days. Here are the steps:
- Inspect. We look at the plaster, sound for hollow spots and confirm an acid wash will help rather than harm.
- Check groundwater and drain. We check conditions, open the hydrostatic relief valve and pump the pool down, discharging where local rules allow.
- Clean. Debris, sludge and leaves come out; the surface is pressure-washed or scrubbed.
- Acid wash. The crew applies a diluted muriatic acid solution section by section, scrubbing and rinsing quickly so the acid takes off the stain without eating more plaster than needed.
- Spot-treat. Stubborn spots get targeted treatment. We may recommend a gentler chemical stain treatment for metal stains rather than more acid.
- Neutralize and remove the rinse water. The acid water is neutralized with soda ash and pumped out.
- Refill and balance. We start the refill and give you start-up chemistry guidance for the new water.
Cleaning options: acid wash, chemical wash or drain-and-clean
Not every pool needs a full acid wash. We'll recommend the least aggressive option that does the job:
| Option | What it does | Best for |
|---|---|---|
| Drain and clean | Drain, remove debris, pressure-wash, refill | High TDS, debris, a fresh start for the water |
| Chemical (no-drain) stain treatment | Targeted treatment with water in | Specific metal stains on otherwise good plaster |
| Acid wash | Removes a thin layer of plaster to strip stains | Overall staining, algae, light scale |
If the plaster is past saving, the next step is choosing a new surface. Compare plaster, quartz and pebble on our pool finishes page.
Acid wash cost and timeline in Denver
A residential drain, clean and acid wash typically runs $600–$1,000, and drain-and-clean only runs $400–$650. Ranges are estimates for the Denver metro, not a quote. Your written estimate sets the price. Water to refill is on your utility bill. Expect 1–2 days on site, plus refill time. We do this work whenever the weather keeps the pool from freezing, generally spring through fall. Many owners pair an acid wash with a waterline tile cleaning or tile and coping work while the pool is empty. Full ranges are in our cost guide.
Featured projects
Drain, clean and acid wash project write-ups appear here as they are added.
Browse more on the projects page.
Why choose us to drain and acid wash your pool
The difference between a good acid wash and a bad one is how much plaster is left afterward.
- Groundwater-aware draining. We check before we drain, and we don't leave pools sitting empty.
- Least-aggressive approach. Short dwell times and quick rinsing to remove stains without stripping more plaster than necessary.
- Honest advice. If an acid wash will only shorten your plaster's life, we'll say so and price a replaster instead.
- Legal discharge. Dechlorinated and routed where local rules allow.
- Insured work. Proof of insurance on request.
Send photos for a free estimate, book a phone consultation, or call (303) 952-8700.