Domakihub How to Acid Wash a Pool and Restore Its Surface
Remove deep stains and algae from your pool shell with muriatic acid — done safely, step by step.
Reviewed by Domakihub pool pros · 2026-06-23 · 5 min read
An acid wash strips away a thin layer of plaster from your pool shell, taking stubborn stains, algae roots, and mineral scale with it. The video above walks through a real professional job; the steps below give you the safety rules, the sequence, and the neutralisation technique so nothing goes wrong. Whether you own a villa on Corfu, a boutique hotel with a rooftop plunge pool, or an Airbnb rental in the Peloponnese, this guide will help you decide whether an acid wash makes sense and how to carry it out correctly.
When does a pool actually need an acid wash?
An acid wash is appropriate when staining, dark algae, or mineral scaling is so deeply embedded in the plaster that brushing and shocking cannot remove it. Common triggers include a pool that has been left unmaintained for a full season, heavy iron or copper staining from well water, or a recurring black-algae problem that returns within weeks of treatment. It is not a routine maintenance task — each acid wash thins the plaster slightly, so most pools can tolerate three to five washes before replastering becomes necessary.
In Greece, pools that are closed without a proper winter cover or left green after the summer season often arrive at acid-wash territory by spring. Holiday-rental operators in particular should assess the shell condition each April before guests arrive, since a visibly stained pool affects reviews regardless of water chemistry.
Safety and equipment you must have before you start
Muriatic acid (hydrochloric acid) is the active ingredient, typically diluted to a 1:10 ratio with water for standard plaster and up to 1:1 for severe staining. It produces fumes that irritate the respiratory system and will burn skin and eyes on contact. Mandatory personal protective equipment includes acid-resistant rubber gloves, chemical splash goggles, rubber boots, and long sleeves. Work in the early morning to avoid peak heat, which accelerates fume production, and never work alone.
You will also need a hose with a running water supply, a stiff-bristle acid brush, a plastic watering can or garden sprayer for application, soda ash (sodium carbonate) for neutralisation, and a submersible pump to remove the neutralised waste water at the end. Keep the soda ash and water mixture already prepared before you pour any acid.
How to acid wash a pool: 5 steps
- 1
Drain the pool completely
Shut off all equipment and drain the pool to zero water level using your main drain or a submersible pump. Inspect the shell once it is fully empty — if you see structural cracks or the plaster is already paper-thin, stop and call a pool plasterer instead. The empty shell will be exposed to sun and air, so plan to complete the entire process in a single day to avoid heat stress cracking the plaster.
- 2
Rinse the shell and mix your acid solution
Wet the entire pool surface with a hose before applying any acid. This prevents the dry plaster from absorbing acid too quickly in one spot and creating uneven etching. Mix the muriatic acid with water in a plastic watering can — always add acid to water, never the reverse — starting at a 1:10 ratio. Have your soda ash neutraliser bucket (roughly 500 g soda ash per 10 litres of water) ready at the pool edge before you descend.
- 3
Apply acid section by section from the top down
Start at the shallow end or top step and work downward in manageable strips of roughly one metre wide. Pour the acid solution onto the plaster, then scrub immediately with the acid brush in circular motions. You will see the acid fizzing as it reacts with calcium deposits and staining — this is normal. Do not let the acid sit for more than 30 seconds in one place; over-etching creates a rough, porous surface that stains faster in future. Rinse each section thoroughly with the hose before moving to the next.
- 4
Neutralise the waste water in the deep end
As you rinse each section, the diluted acid and wash water will collect in the deep end. Once you have finished all surfaces, pour your soda ash solution into the collected liquid and stir with a brush. Test with pH paper — you want a reading of 7 or above before pumping the waste out. Many Greek municipalities require diluted acid wash water to be trucked off-site rather than discharged to the storm drain; check local rules or contact your water authority before disposing of the waste.
- 5
Refill and balance the water chemistry
Once the waste is removed, rinse the entire shell one final time, then begin refilling immediately to prevent the freshly etched plaster from drying out and cracking. As the pool fills, add a start-up dose of pH increaser and alkalinity increaser, because new plaster and freshly acid-washed surfaces will drive pH down aggressively for the first two weeks. Run the pump continuously for 24 hours after filling, brush the walls twice daily for ten days, and retest chemistry every 48 hours until the water stabilises.
Rather have a pro handle it?
Get a vetted pool pro in your city — one number, booked in EN/EL/DE.
FAQ
- How often should I acid wash my pool?
- Most plaster pools can handle an acid wash every five to seven years before the surface becomes too thin to safely treat again. Washing more frequently shortens the life of the plaster. If staining returns quickly after a wash, investigate the root cause — high iron in the fill water, persistent algae, or an imbalanced pH — rather than re-washing.
- Can I acid wash a pool with a vinyl liner or fibreglass shell?
- No. Muriatic acid will immediately damage a vinyl liner and can blister or cloud a fibreglass shell. Acid washing is only appropriate for plaster (marcite), aggregate, or pebble-finish surfaces. For fibreglass pools, use an oxalic acid stain remover formulated specifically for that surface, applied while the pool is still full.
- Is it better to hire a professional for an acid wash?
- For most homeowners and rental operators, yes. The chemical hazard, waste disposal requirements, and risk of over-etching the plaster make it a job where professional experience pays off. A pool technician will also be able to spot underlying problems — cracked plaster, failing bond coat, or structural leaks — that are only visible on a drained shell.