How to Acid-Wash a Plaster Pool Surface

A pool with a plaster surface will absorb dirt and chemicals and will need to be acid-washed every two to three years. This process is usually completed as a first step to repainting the pool surface. The acid etches the surface of the plaster, creating the best environment for a successful paint job. The acid-washing procedure is messy and involved, but is necessary to achieve a clean surface to which the paint will be able to bond.

Things You'll Need

• Power washer
• Thick rubber gloves
• Chemical suit
• Rubber boots
• 5-gallon bucket
• Stiff long-handled brush
• Muriatic acid
• Trisodium phosphate

Instructions

1. Wear a chemical suit that can be purchased at most home improvement stores. Wear thick rubber gloves and tuck the bottom of the suit into the rubber boots. This attire is especially important when you use the acid wash.

2. Wash the surface of the pool thoroughly with a power washer. Hold the end of the power washer wand 2 to 3 feet from the surface of the pool and make sure to wash every inch of the pool surface.

3. Pour 1 gallon of muriatic acid into 1 gallon of water in a 5-gallon bucket. If the pool is especially large, you can mix more acid wash by using the same 50-50 mixture of acid to water. Always add acid to water -- not water to acid -- to avoid a violent chemical reaction.

4. Scrub the entire surface of the pool with the acid wash and a long-handled scrub brush. Dip the brush into the bucket often to keep it soaked. Scrub the surface using moderate pressure.

5. Mix 1 cup of trisodium phosphate with 1 gallon of water and scrub the surface of the pool with the mixture and the long-handled scrub brush. Mix larger quantities using the same ratio. The trisodium phosphate will neutralize the acid before painting. Rinse the surface with a garden hose.