Pool Acid Wash: What Is It & Does Your Pool Need One?

An acid wash is one of the most effective ways to restore a pool’s interior surface — stripping away stains, algae residue, and mineral deposits to reveal clean plaster underneath. But it’s not a routine procedure, and knowing when (and whether) your pool actually needs one matters.

What Is a Pool Acid Wash?

An acid wash — sometimes called a drain and acid — involves draining the pool completely and applying a mixture of muriatic acid and water directly to the plaster surface. The acid dissolves a thin layer of the plaster, removing embedded stains, algae roots, and mineral discoloration that normal cleaning can’t touch.

The result is a noticeably brighter, cleaner surface. On a white plaster pool, the difference is often dramatic.

When Does a Pool Need an Acid Wash?

Not every pool needs one, and not every stain warrants the procedure. An acid wash is appropriate when:

• Persistent staining — You can see the bottom, but the plaster has widespread discoloration that won’t respond to chemical treatment
• Post-algae recovery — A severe algae bloom (especially black algae) has left staining embedded in the plaster
• Neglected pools — The pool sat unused for an extended period and the surface is heavily discolored
• Pre-sale preparation — Restoring the pool’s appearance before listing a property
• Routine interval — Many pool professionals recommend an acid wash every 5–7 years, depending on water chemistry history and surface condition

An acid wash is not appropriate when:

• The plaster is already thin or heavily worn (acid removes material — there’s a limit)
• The pool has a pebble or exposed aggregate finish (different process required)
• Staining is caused by metals in the water (copper or iron stains need chemical sequestrant treatment, not acid)

The Acid Wash Process

A professional acid wash follows a specific sequence:

1. Pool is fully drained using a submersible pump — never the pool’s circulation pump
2. Debris is cleared from the empty pool
3. Acid solution is applied in sections, working from the top of the walls downward
4. Each section is scrubbed and rinsed before the acid can dry on the surface
5. Rinse water is neutralized (typically with soda ash) before disposal
6. Pool is refilled with fresh water
7. Full chemical startup — pH, alkalinity, calcium hardness, chlorine, and CYA are balanced from scratch

The entire process typically takes one full day for a standard residential pool. The pool should never sit drained longer than necessary, particularly in Arizona.

Plaster Types and Acid Wash Compatibility

Not all pool surfaces respond the same way:

• White plaster — Ideal candidate for acid washing. Responds well and shows the most dramatic improvement.
• Colored plaster — Can be acid washed, but results vary. The acid may lighten the color unevenly, especially on older surfaces.
• Pebble finishes (PebbleTec, PebbleSheen) — Standard acid washing is generally not recommended. These surfaces require gentler cleaning methods or specialized treatment.
• Tile — Tile itself is not acid washed. The tile line is typically cleaned separately using bead blasting or chemical treatments.

If you’re unsure about your surface type, a pool professional can assess whether an acid wash is the right approach.

Timing in Phoenix

Like any drain procedure, acid washing in Phoenix has a strict seasonal window. October through March is the safe range. During summer months:

• Temperatures above 100°F can damage exposed plaster rapidly
• Direct sun on an empty pool shell causes cracking and delamination
• Monsoon storms can flood an empty pool with debris-laden water

The sweet spot is late fall through early spring when daytime highs stay below 90°F and the risk of rain is minimal.

Cost Considerations

Acid wash pricing typically depends on pool size and surface condition. The service generally includes the drain, the acid wash itself, refill coordination, and chemical startup. Water cost for refilling a typical 15,000–25,000 gallon residential pool runs $60–120 at Phoenix-area water rates, which is usually a separate cost from the service itself.

A heavily stained pool may require a double acid wash — two passes instead of one — which increases the service cost accordingly.

How Many Acid Washes Can a Pool Handle?

Every acid wash removes a thin layer of plaster. A standard plaster surface is applied at roughly 3/8” to 1/2” thick. With each acid wash removing a small amount, most pools can handle 5–8 acid washes over the life of the plaster before a replaster becomes necessary.

If the plaster is already rough, thin, or showing aggregate underneath, it may be time to replaster rather than acid wash again.

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Considering an acid wash for your pool? Contact Splash Mob Pools to schedule a surface assessment and get a clear recommendation.