Acid wash or resurface? A plain English guide

Acid wash it if the plaster underneath is still sound, and resurface it if the plaster itself is worn out. The stain is not what decides it. The surface is.

An acid wash strips a very thin layer off the top of the plaster, and the staining goes with it. That only helps if there is good plaster left underneath. If the surface is already breaking down, washing it just removes more of what is left and the pool looks rough again within months.

Run a fingernail across the worst looking patch. If it feels smooth and the discoloration is sitting on top of the surface, a wash will very likely take it off. If it feels chalky or rough, or a little comes off on your finger, the plaster itself is finished.

Other signs that point to a resurface rather than a wash:

• Rough patches that snag swimsuits or scrape feet
• Flaking or pitting, especially on the steps and the floor near returns
• Spots that sound hollow when tapped, which means the plaster has let go of the shell
• Cracks you can catch a nail in

An acid wash removes stains that sit on the surface: organic staining from leaves and algae, and metal staining from well water. It does nothing for etching, rough plaster or cracks.

Metal staining comes with a catch. It washes off, but it comes right back unless the refill water gets treated, because the iron is still in the well. If that is your situation, read how to remove well water stains from a pool before you book anything.

Two or three times over the life of a plaster surface is realistic. Every wash takes a little plaster with it, so each one shortens the time until a resurface.

We count them the same way you would. That is why we will sometimes tell a customer the money is better spent resurfacing than on one more wash that buys eighteen months.

It lasts as long as you keep the cause away. Organic staining on a well kept pool can stay gone for years. Well water staining comes back in a season or two if the fill water is not treated, and a green pool that gets left again will stain again.

The wash fixes what is on the surface. Steady chemistry and a weekly pool service are what keep it that way.

The pool is drained, the plaster is washed down section by section with a diluted acid solution and rinsed, the acid is neutralized, and the pool is refilled and balanced.

The draining is the part that needs care in Florida. With a high water table an empty pool can lift out of the ground, so it should be empty only as long as the job takes, and drained in drier weather where possible. There is more on that in should I drain my pool. Pool acid is also a chemical to treat with respect, which is one more reason this is not a weekend project. The CDC is clear that pool chemicals should be stored and handled so they never mix.