There are two main reasons to Acid Wash. First is more of a maintenance issue. Every three to four years the pool should be drained and lightly acid washed. This helps remove bad guys from your plaster or pebble tech finish.
This should be done in the off-season. Its not good to drain a pool once we hit 100 degrees steady. The heat can dry out the plaster unusually fast compared to say October.
The acid wash process starts with draining of the pool into the sewer P trap this is located in your front yard usually up against the house. Then we mix several additives to the acid to tone it down and remove stains. Done properly this will leave your pool as smooth as before the acid wash or smoother. Done improperly, the pool will end up like sandpaper due to what we call etching. This is where an inexperienced or cheap pool guy will just use acid and water. The acid instantly reacts to the plaster and attacks it. This can cost you up to $8,000 for a large pool to resurface, so spending a few extra hundred beats spending thousands. I have acid washed over a thousand pools and understand it’s better to leave a difficult stain on the plaster than use acid and water to burn it off. I sometimes will use fine grit sand paper to remove a difficult stain.
The next reason to acid wash is to remove black and green algae. This can be a very difficult situation. I have acid washed pools where the water was almost black it had been sitting stagnant so long.
This can be very dangerous now with West Nile virus infected mosquitoes in the area. One green pool can affect an entire zip code, as mosquitoes can travel far distances to feed. Again we mix acid water and several special additives together and pour the solution on the walls. Then we scrub the plaster, rinse then repeat if necessary. Then final step would be a chlorine bath. This is where we mix liquid chlorine and water together to make a final algae killing mix. This gets poured on the plaster and then we fill the pool.
Fair market value for a drain, acid wash and start-up chemicals starts at $600 and goes as high as $1,500 for a large green pool. Add an extra $100-150 to clean the filter or $400.00 for new cartridges. New cartridges are best if the pool turned green or black.