Is your pool looking dull? Maybe it has a few stains here and there? Is scrubbing and vacuuming just not getting it totally clean anymore? Sounds like it may be time to acid wash your pool.
Before you jump into it, though, we highly encourage you to read this entire article from beginning to end. Working with acid is not to be taken lightly, and you want to avoid damaging your pool. But more importantly, you want to stay safe. And we want you to stay safe.
What Does it Mean to Acid Wash a Pool?
We’re not just talking about a regular cleaning here. Anytime you include the word acid, it should be clear you’re not talking about a regular anything. You’re bringing out the big guns when you acid wash a pool.
You know how you can go to a dermatologist and have your face exfoliated with a mild acid? The thin, top layer of skin is removed, revealing newer, younger skin underneath. Of course, you’ll look like you have a sunburn for about a week, but the end result is a smoother, brighter complexion. That’s what an acid wash does for your pool.
More than just a surface clean, an acid wash actually strips a thin layer of plaster off the surface of the pool. Along with the plaster layer, stains left by chlorine, algae, minerals, and just plain dirt are removed, exposing a fresh, clean layer of plaster underneath.
Does removing plaster sound alarming? Don’t worry. Usually, a pool’s plaster coating is at least ½ an inch thick, and the acid removes a very thin layer.
What Kinds of Pools Can be Acid Washed?
This should be pretty self-explanatory, but let’s be clear, just in case. You will only acid wash an inground concrete or gunite pool.
An acid wash is not something to ever do on a vinyl-lined inground pool, or on an above ground pool. The acid will eat right through that vinyl, and then you’re looking at replacing the liner altogether.
When to Acid Wash Your Pool
No matter how well you keep up with pool maintenance and water balancing, your pool floor and walls will eventually start to see some wear.
Chlorine, minerals, and dirt will leave stains over time. If you get to the point where brushing and vacuuming aren’t working anymore, it might be time for an acid wash.
If you’ve ever had an algae problem, that might’ve left some staining as well. Or, if you encounter repeated algae blooms, you might not be getting all the spores off with regular cleaning. An acid wash will remove those spores, and let you start over with a fresh, algae-free surface.
Acid washing for algae is a last resort, though. Try other methods to get rid of pool algae first. Then, if you decide to acid wash your pool, be sure to also change your pool filter media to make sure there’s no algae residue in there, either.
If your pool has sat stagnant for a while, allowing algae and dirt to really set in, only an acid wash will bring the pool back to life. If you don’t properly winterize your pool, that counts as stagnation, and may also affect the appearance of the plaster.
In some cases, you may not need to acid wash the entire pool. For example, if you’re doing some pool plaster repair, acid washing the spot you’re working on can get rid of algae before you apply new plaster. Can you imagine if algae spores were mixed in with the new plaster? You’d never get rid of them, and the algae would just keep coming back over and over.
Wear and Tear
Sometimes, it’s not stains, algae, or stagnation that necessitate an acid wash. It may just be that the plaster is discolored or faded from years of chemicals and being exposed to the hot sun. In those cases, an acid wash will improve the appearance of your pool, and bring back the clean, clear look it started with.
How Often to Acid Wash Your Pool
Even though an acid wash will only remove a thin layer of plaster, it’s not something you want to do every year. You’d run out of plaster pretty quickly!
Every five years or so is sufficient, barring any serious algae bloom problems.
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Did we mention we’re talking about using acid? It’s a caustic substance that requires specific and consistent precautions to avoid injuries.
Wear the Right Kind of Mask
The type of acid you use to acid wash a pool—muriatic acid—gives off noxious fumes. It can cause respiratory difficulties, especially if you already have an upper respiratory condition such as asthma.
So when you take on this task, not just any mask will do. You need one that will block acid fumes.
Wear the Right Kind of Gloves
Gardening gloves, dishwashing gloves, work gloves—no. None of those are enough. You need chemical-resistant gloves that specifically resist acid to ensure the acid doesn’t eat through the material and reach your hands.
If you do happen to get any acid on your skin, rinse it off immediately, and keep the spot under running water for at least 30 seconds. You may still end up with a slight burn, but it won’t be too bad. If you don’t rinse the acid off right away, though, you can end up with a serious burn.
When you’re done acid washing your pool, rinse the gloves off thoroughly, and apply some soda ash to them to neutralize any acid residue. Then rinse them again before removing them.
Wear Safety Goggles
Acid may not do much damage to your skin (as long as it’s rinsed off quickly). But it can seriously hurt your eyes. If the acid damages your cornea, you may even lose your sight. Literally.
Always, always, always wear safety goggles when working with acid. Put them on before you begin, and don’t take them off until you’re done, the acid is neutralized and put away, and you’ve removed the gloves that were touching acid. Rinse and dry the goggles before storing them.
Important: If acid happens to splash into your eye, thoroughly rinse your eye with clean water for a minimum of 15 minutes. Do not rub your eye. When you’re done rinsing, seek medical attention immediately.
Wear Appropriate Clothing
It may be hot out when you decide to acid wash your pool, but we highly recommend you wear long pants, a long-sleeved shirt, and closed-toe shoes.
All it takes is one tiny splash of acid on your skin, and you can end up with a burn, and possibly a scar. And if you were to drop the acid container, and a bunch of it splashed on you? We don’t need to describe that scene, do we?
Note: Chemical-resistant boots are your best choice for footwear when you acid wash a pool. Make sure they resist acid. Remember to rinse them off before exiting the pool. And remove them before you go back into your house.
Note for Women: If you have trouble finding a pair of women’s chemical-resistant boots, use a size conversion chart to choose a man’s size that will fit you.
Avoid Acid Splashes
The best way to do this is to pour the acid slowly. And then set the acid container down slowly and gently so none of it splashes out.
When you’re not using the acid, tightly seal the container and set it out of the way where it can’t be knocked over.
When you’re done acid washing your pool, put the acid container away in a cool, dry space that can’t be accessed by children or pets.
Dilute Acid in the Right Order
You’re not going to add full-strength acid to your pool surfaces. It will eat away the plaster before you can rinse it off. You’ll need to dilute it first.
Always add the acid to the water you’re diluting it with. Never add water to acid. It can cause a boilover.
When acid and water are mixed, a large amount of heat is produced. If you add acid to water, the majority of the compound is water, which controls the heat, and prevents the mixture from boiling over.
If you add water to acid, the compound produced is mostly acid, and the amount of heat released will cause the mixture to immediately and violently boil over and splash out of the container.
Because the compound is still mostly acid at that point, what splashes out will be extremely caustic, and can burn you and the surrounding area.
So once again: Always add acid to water, never the other way around.
Important: Don’t let any other chemicals come into contact with acid. Depending on the chemical, toxic fumes, small explosions, or both can result.
Keep Kids and Pets Away
While you’re in the process of acid washing your pool, children and pets should not be anywhere near the pool area. You might think, it’s OK for them to watch from a few feet away where they can’t get splashed.
But remember, acid gives off fumes, and if the wind is right, your child or pet can inhale those fumes, which may damage their lungs.
It’s not worth taking any chances. Keep kids and pets inside and completely away from the pool area during an acid wash.
Don’t Acid Wash Your Pool on a Windy Day
If the day you choose to acid wash your pool turns out to be windy, reschedule. You don’t want acid fumes blowing into your home or the neighbor’s yard where they can injure someone.
Don’t Rush the Job
You’ll need to work quickly to keep the acid from doing any damage. But trying to rush through a process is just asking for trouble. It’s how mistakes are made.
Read all the directions first, have everything you need on hand, and closely follow all instructions.
Keep the Pool Deck Clear
Falling into a pool full of water usually won’t hurt, unless you hit the water belly first. But falling into an empty pool can be lethal.
Clear the pool deck of all chairs, toys, planters, and anything else that may present a trip hazard while the pool is empty. And stay aware of your surroundings while you acid wash the pool. Make sure anyone who’s helping you is also cognizant of the potential dangers.
Have a Wastewater Disposal Plan
You’ll need to know how to dispose of your pool water when you drain it in order to acid wash it. Some cities and municipalities have strict regulations about wastewater disposal. You may even be fined if you don’t follow those rules.
More importantly, you’ll need to know how and where to dispose of the acid/water mixture you’ll be left with when you finish washing your pool. Even if the acid mixture has been neutralized, it can still damage plant life, and even kill animals.
Before you start to acid wash your pool, check with your local water authority about how to properly dispose of the pool water and the acid/water mixture.
Follow the Manufacturers’ Instructions
In addition to all the safety precautions we can think of, you may find a few more on the manufacturers’ labels. Read them before you even open the acid container, and follow them to the letter.
Disclaimer: We are not acid experts or doctors. The precautions we’re outlining here are based on experience and common sense, but we are not responsible for any accidents that may occur, whether you follow these precautions—and the manufacturer’s—or not. Do your due diligence and make sure you’re doing everything you can to avoid injuring yourself and others. If you don’t feel you can maintain a safe environment when using acid, hire a professional to acid wash your pool.
Do not take the handling of acid lightly. Wear the recommended safety gear, and follow all instructions both for the process, and on the manufacturer’s labels to ensure your safety and well-being.
The Acid Washing Process
Before you begin, make sure you have everything you need handy. You don’t want to have to stop mid-wash to run to the pool or hardware store.
What You’ll Need
- submersible pump (with a power cord long enough to reach to the bottom of the deep end without an extension cord)
- drainage hose
- 2 garden hoses (long enough to reach all areas of the pool)
- spray nozzle
- algae brush
- acid brush with a long handle
- watering can with a long spout and a showering end or attachment
- water test kit
- Acid Magic Muriatic Acid Replacement
- soda ash, also called washing soda
- safety goggles
- acid safety mask
- acid-resistant gloves
- long pants
- long-sleeved shirt
- acid-resistant boots
- a friend or family member to help out
Note: You could use regular muriatic acid to acid wash your pool. But we recommend Acid Magic because it’s not as strong and doesn’t produce as many fumes, but is just as effective. It’s still acid, though, so be sure to take all the proper safety precautions to prevent injury.
1. Drain and Clean the Pool
Follow detailed instructions for how to drain a pool to avoid causing expensive damage to your inground pool.
As the pool drains, use the algae brush scrub all the surfaces to remove dirt, debris, and algae (if there is any) before it can dry. Once it’s dry, it’s much more difficult to remove.
As the water level drops, wet down the surfaces with the hose and spray nozzle to remove the debris you just scrubbed off, and to keep the plaster from baking in the sun.
Once the pool is empty, collect any debris that was too large to drain out (leaves, twigs, etc.), and rinse any remaining dirt from the floor.
Note: After the pool is drained, if you pressure wash it, you may be able to use less acid for the wash. This will also depend on what kind of condition your pool is in.
2. Replace the Hydrostatic Pressure Relief Valve
You will have removed one or more valves when you drained the pool. Replace them now to prevent any acid mixture from seeping into the groundwater.
3. Dilute the Acid
In the watering can, add equal parts Acid Magic (or muriatic acid, if you prefer) to water. If you pressure washed your pool after draining, and it made a difference in the plaster’s appearance, you can try adding less acid than a 1:1 ratio. The less acid you can use, the better as it will be gentler on the pool plaster.
4. Prepare the Garden Hoses
Be prepared to use a lot of water here. Connect one garden hose to a spigot, put the other end in the pool, and turn the water on. Do not connect a spray nozzle to the hose. Keep the water running.
Connect the second garden hose to another spigot, put the other end in the pool, attach the spray nozzle, and turn the water on. Keep the water running.
5. Acid Wash the Pool
It’s showtime! Start in the bowl of the deep end—the area around the drain. Work in sections. Use the hose without the nozzle to wet down the surface before you pour the acid mixture onto it. Pouring acid onto a dry surface can damage the plaster.
Pour the acid mixture in a circular pattern, and have the person helping you follow behind with the acid brush and scrub the surface. Let the mixture sit for 30 to 60 seconds, depending on how dirty it is.
Rinse the scrubbed area with the spray nozzle, then add a few pounds of soda ash to the water that collects in the bowl to neutralize the acid in it.
Continue to work your way around the bottom of the pool, pouring, scrubbing, and rinsing.
When you’re done with the floor, move to the walls, again working in sections. Start with the shallow end steps. Pour the acid mixture from the top of the pool wall, letting it run down, with your helper following behind, scrubbing the walls (Or you might want to take turns. If you make them do all the scrubbing, you may not have a friend by the end of this task.). Let the mixture sit for 60 to 90 seconds. Rinse.
Continue to work your way around the pool walls, pouring, scrubbing, and rinsing, and finishing up in the deep end.
Note: If the 1:1 acid mixture isn’t fully removing stains or brightening the plaster, you can increase the strength of the mixture, or try scrubbing a little harder, or both. You can also go over problem spots a second time with a weaker acid mixture.
6. Neutralize the Acid as You Go
Even though you added some soda ash to the deep end bowl when you started, you’ll need to continually add more as you add more acid to the pool. This will ensure the growing puddle of wastewater remains neutral (or as close to neutral as possible), which will keep the acid from etching the bottom of the bowl, and help prevent any accidents should someone trip and fall into the water.
You’ll also need to ensure the water is neutral before you dispose of it to prevent environmental damage.
Approximately 2 pounds of soda ash per 1 gallon of acid should be sufficient to neutralize the mixture.
Important: Check the manufacturer’s instructions on both the acid and soda ash to make sure you use an appropriate ratio for neutralization.
As you work, broadcast the soda ash over the puddle, and stir it in with the acid brush or your telescoping pole.
When you’re done with the acid wash, you’ll have a large, foamy puddle of wastewater at the bottom of the deep end.
7. Test the Acid/Water Mixture Before Disposing
Use the water test kit to test the collection pool’s pH level. Try to get the water as close to neutral as possible, adding more soda ash if necessary.
8. Pump Out the Wastewater
Break out the submersible pump you used to drain the pool, and set it up in the collection pool. Once it has drained as much water as possible, rinse the deep end with clean water, and pump that out.
Because the dirty water will sit on the floor of the deep end for a while, it may cause a little staining in that area. If this happens, drain, rinse, and then pour a weak acid/water solution over the spot to clean the plaster. Scrub if necessary, then rinse.
Neutralize that water and dilute it. Then pump it out.
Important: Refer back to your wastewater disposal plan to ensure you’re following local regulations, and not harming the environment or any animals by improperly disposing of acidic water.
9. Rinse the Deep End Again
Rinse the deep end floor one more time, and pump out whatever water is left.
10. Refill the Pool
After you’ve ensured the deep end bowl is clean and free of any wastewater or acid, you can start refilling your pool.
Acid Washing Precautions
You’ll need to take certain measures during the actual acid washing process to prevent damage to your pool.
- Do not let the acid mixture sit on any surface for too long. It can damage the plaster.
- Acid does not naturally deplete. It must be rinsed away or it will continue to eat away at the plaster. Triple rinse horizontal surfaces like steps or swim-outs where acid can collect.
- Do not use a pressure washer to rinse the acid mixture away. The strong blast will spray the acid mixture onto surfaces where you don’t want it, including yourself. The regular hose nozzle is fine.
- Keep the acid from wearing a path into the floor plaster by using the acid brush and the spray hose to continually move it toward the collection pool in the deep end bowl.
You Can Always Hire a Pro
So what do you think? Does this sound like something you can do? Of course it is. But is it something you want to do? Maybe not, and that’s OK. Draining your pool is a big deal that can cause damage if done incorrectly, and working with acid can be nerve-racking.
If you’re at all uncomfortable with any part of the process to acid wash a pool, don’t hesitate to hire a pro. You’ll be able to rest easy knowing everything will be done right. Then all you’ll have to worry about is getting back to enjoying your pool. Well, and that big water bill.