Acid washing a plastered pool etches away a thin layer of plaster, revealing the cleaner plaster beneath. For this reason, acid washing should not be an annual occurrence. One every 5 years or so should be plenty. Acid washing is a dangerous process that involves the use of strong chemicals, so it’s often best to let professionals acid wash your pool. If you plan to do it yourself you will need detailed instructions. But this outline will give you an idea of what the pros do.
Acid Washing a Pool is not a DIY Project
Sometimes a pool can get to a point where chemicals in the water alone will not work to clean it. If a pool is well maintained, it shouldn’t get to that point. But if there has been extensive algae bloom and debris has been left at the bottom of the pool for too long, you can end up with a real problem.
If your pool has become so dirty that you can’t see the floor of the shallow end, you may need an acid wash. An acid wash is by definition a destructive process. You are using strong acid to burn away a thin layer or plaster to reveal cleaner plaster below. So this is not something you should be doing unless your pool really needs it.
Because acid washing uses harsh chemicals that can be dangerous to work with, it is best left to the professionals. The Pool Butler can help. This article will give you an idea of what’s involved, but acid washing is rarely a do it yourself project.
NOTE: The full detailed instructions for safely and correctly acid washing a pool are complex. This outline is really just to give you an idea of what is involved. If you decide to do it yourself, DO NOT USE THIS GUIDE ALONE. Make sure that you have detailed instruction and/or guidance from a professional.
Working With Harsh Chemicals
When beginning an acid washing project, the first step is to be properly protected. Wear long sleeves and long pants to protect your skin. Sometimes the pros will have a special protective outfit. They will also wear old boots or shoes, or use rubber boots, because the acid can bleach shoes. Most important, they will make sure they have a proper breathing mask rated for acid fumes, as well as protective eyewear.
Because the cleaning process will create puddles of acid water, the cleaners will need to neutralize them before pumping out the waste water. It takes about 2 pounds of soda for every gallon of acid to neutralize the waste water.
Draining a Pool
The first thing the cleaners will have to do is to drain the pool. Make sure to check with local authorities about guidelines for disposing of waste water. Pool water has chemicals in it that should not just be drained anywhere.
As soon as the pool is drained, the cleaners will have to remove the hydrostatic relief valve plugs. A hydrostatic relief valve is a tube underneath a plaster pool the leads to a gravel base. It allows groundwater to filter up into the pool instead of lifting the pool and causing serious damage. With the pool water gone, the pressure from groundwater needs to be released. Opening the hydrostatic relief valve relieves this pressure. Some water may bubble up, or even come up in a geyser. That’s a good thing, as it is relieving any pressure from underneath the pool.
As the pool is draining, the cleaners will have to scrub the walls clean of algae and other gunk. Scrubbing while the walls are still wet is much easier than trying to remove algae and other gunk once it has dried onto the walls of the pool.
Pouring the Acid
Once the pool is drained, the cleaners can begin to apply the acid. The acid is added to water to create a 1:1 solution, or sometimes a slightly weaker mix. It is best to use as little acid as needed to get the job done. Using a long necked flower watering pot or a similar utensil, the acid solution is poured onto the surface of the pool.
The acid application begins at the deep end of the pool closest to the drain. This is done because that area will quickly fill with waste water. During this whole time, the surface of the pool should be kept moist. This can be done with a hose with no nozzle on it, gently pouring water over the area. Never use a power washer.
While washing the area around the drain, have a helper with a stiff broom push the acid solution around. After the acid is applied, the cleaners should rinse the area with plenty of water, then add a few pounds of pH increaser to neutralize the waste water.
After cleaning the area near the drain, move to the shallow end of the pool. Start with the stairs area and pour the acid solution beginning with the top of the walls and working your way down. Use an acid brush to scrub and spread around the acid. Always keep a flow of water and make sure to rinse each area thoroughly after applying the acid solution. Don’t let the solution sit or run in a small line down toward the drain end of the pool. This could leave scars on the plaster where the acid burns away more plaster than you need to.
Neutralize the Waste
When the acid application is done, there will be a large puddle of wastewater at the deep end of the pool. This will need to be neutralized before it can be disposed of. Use plenty of pH increaser, such as soda ash. It takes about 2 pounds of soda ash per gallon of acid to fully neutralize the wastewater. You can also use a pH tester to make sure the water is as close to pH neutral as possible.
Once the water is neutralized, it can be pumped out of the pool. Use a submersible pump to get all the water out of the deep end. Make sure to check with local authorities about proper disposal of waste water. Avoid pouring the water near plants, as even the neutralized water can kill off vegetation.
Replace Drain Covers and Refill Pool
When the pool is empty, do one final rinse with plain water. If you are asatified you can start to seal things up. Replace the drain covers and close up any hydrostatic relief valve plugs you removed. If the bowl of the pool still looks dirty, you can apply the acid one more time to the deep end, making sure to neutralize and rinse after.
Now it is time to refill the pool and enjoy your sparkling new plaster.
Don’t Try This at Home
The above outline gives some information about how a pool is acid washed, but it is not intended as a full instructional guideline. There are many details to doing a proper acid wash. Most importantly, the safety of all workers must be ensured. That includes safe handling of harsh chemicals and extra safety precautions around a drained pool. And even when safety protocols are followed, a misuse or wrong application of the acid solution could damage your plaster.
If your pool looks bad enough that you think it needs an acid wash, contact the specialists at The Pool Butler for a consultation. We will help to diagnose your problem and develop a plan to get your pool back to pristine condition.