How to Acid Wash a Pool For a Deep Clean

Written by Michael Dean
October 12, 2023

two workers acid washing a swimming pool

Even if you are consistent with your pool maintenance routine, there may come a time when the algae buildup and staining on your pool plaster get too much for traditional cleaning methods. If your pool’s surfaces have algae growth that is seemingly impossible to eliminate or the walls are stained from dirt and debris, you may consider acid washing your pool. Acid washing is one of the best ways to restore your swimming pool to its original out-of-the-box look.

In this article, I’ll walk you through the best way to safely acid wash your pool, when to acid wash your pool, safety precautions you should take, and review some common questions on the topic. If you already have your supplies and safety gear, you can jump right to the acid washing steps. Let’s dive in!

Main Takeaways

  • Acid washing is a cleaning process that uses muriatic acid to remove stubborn stains, debris, and algae from the pool surface.
  • You should acid wash every 5-7 years or when your pool has permanent stains, faded plaster, stubborn algae growth, or stains from hard water.
  • Make sure to follow all safety precautions when handling muriatic acid, including wearing proper PPE gear and always adding acid to water and not the other way around.
  • It is possible to acid wash without draining the water, but it may not be as effective.

What is Acid Washing?

Acid washing is essentially what it sounds like using acid to clean the surfaces of your pool. This may seem like an extreme way to clean your pool, but it is one of the best ways to get all that stubborn algae off the walls. Acid washing a pool involves draining the water, making an acid solution using water and muriatic acid, and scrubbing the walls with the acid using a brush.

What Type of Pool Should Be Acid Washed?

An inground pool with stubborn algae growth or other surface stains may need to be acid washed to be effectively cleaned. Acid washing pool plaster is also a critical step in the installation process for new swimming pools. You should never acid wash a pool with a vinyl liner or any type of above ground pool. The acid will eat away at the liner and form holes. Only acid wash inground pools made of gunite or concrete.

When is it Time to Acid Wash Your Pool?

If your water is constantly murky or the surfaces have permanent stains, keeping up your cleaning schedule may not be enough, and it could be time to acid wash the pool.

If you are consistent with your pool maintenance, you shouldn’t have to acid wash your pool often. Every 5-7 years is the usual benchmark. I do not recommend acid washing more often because the harsh muriatic acid can damage the pool’s surfaces when overused.

Visually check your pool when doing your weekly maintenance. It may be time to acid wash your pool if you notice the following signs.

Permanent Stains

Staining can come from rust, mold, or other debris. If the stains have been there for a while and your traditional cleaning methods don’t seem to be working, it may be time to acid wash.

Faded Plaster

The color of plaster or cement in your pool may start to fade over time. An acid wash can bring back the original color of the plaster. Remember that this won’t always work, depending on the severity of the fading.

Stubborn Algae Growth

If your pool has been stagnant for some time or your pump is not circulating the water properly, algae and dirt can settle into the pool walls. This can be very difficult to clean properly. And when all else fails, you need to know when to drain your pool and give it a good scrub with muriatic acid.

Hard Water

Excessive amounts of calcium in the water can lead to hard water stains, also called scum. These calcium deposits can usually be found around the edge of the pool. Hard water stains lead to unsightly, cloudy water and an unbalanced pH level. These stains can be removed with an acid wash.

Returning your pool to pristine condition requires a little work, but the results are worthwhile. An effective acid wash and cleaning can help return your pool to normal.

Safety Precautions

Before you begin an acid wash, you must take the proper safety precautions. Muriatic acid is caustic and only slightly less corrosive than hydrochloric acid, so it can quickly eat through your clothes and irritate your skin and eyes.

Wear acid-resistant gloves: Protecting your skin is paramount when handling muriatic acid. Standard rubber gloves will not do, so make sure to buy heavy-duty, latex-resistant gloves.

Wear a mask that blocks fumes: Muriatic acid can give off dangerous fumes; you’ll need to wear a respirator mask designed to block noxious fumes.

Wear appropriate clothing: When handling acid, it is unacceptable to wear open-toed shoes, shorts, or a t-shirt. Instead, wear full-cover clothing that you don’t mind getting damaged.

Wear eye protection: Your eyes are even more sensitive to acid than your skin. You can even lose your eyesight if acid splashes on your face. So, make sure to wear proper eye protection.

Keep the surfaces wet: When scrubbing your pool with the acid solution, keep surfaces constantly wet with clean, fresh water. Also, keep the solution moving toward the drain at all times. Otherwise, you may develop dips and dents on the surface of your pool.

Always add acid to water: When diluting your acid solution, the acid should be poured into the water, not the other way around. Adding water to the acid can create a chemical reaction that will cause the acid to bubble and splash. So make sure to fill a bucket with water before adding the acid to dilute.

Store the acid properly: Always store the muriatic acid in the original container and keep it away from other incompatible chemicals. Another top tip is to properly label the muriatic acid.

In addition to a handful of safety supplies, you need the tools and equipment to complete the acid wash job. If you don’t own a drainage pump, several garden hoses, or a specialized acid-resistant scrub brush, you’ll likely need to make a quick shopping trip.

Supplies Checklist

Before you acid wash your pool, you’ll need to have the following supplies on hand.

  • Muriatic acid
  • Safe clothing, glasses, gloves, and boots
  • A powerful submersible water pump
  • A long drainage hose
  • An extended garden hose
  • Soda ash
  • Water testing kit
  • Algae brush
  • Acid resistant brush
  • High-pressure spray nozzle

You should also ensure that you have access to clean running water and a sewer. If your garden hose cannot extend from your water source to your pool, purchase a longer one or an extension hose. Check that your drainage hose is long enough to reach the nearest sewer opening.

Finally, double-check the durability of your safety apparel. If it’s not acid-resistant, I recommend investing in equipment that can handle contact with corrosive chemicals.

Step-by-Step: How to Acid Wash a Pool

Once you’ve gathered your supplies, it’s time to get started. Ensure your safety gear is properly secured and positioned, taking special care to protect your skin, lungs, and eyes.

While you could tackle this project alone, consulting a professional when draining an inground backyard pool may be wise. Hiring a pool maintenance crew to acid wash your pool could help you save money on equipment, ensure the cleaning goes smoothly, and prevent costly or painful accidents.

Here are the steps to acid wash your swimming pool:

  1. Drain the pool
  2. Scrub the surfaces
  3. Prepare the acid solution
  4. Scrub and rinse surfaces
  5. Make the wastewater safe
  6. Drain and refill
  7. Balance the chemical levels

Let’s dive into each step in more depth.

Step 1: Drain the Pool

Attach the drainage hose to your submersible pump and drag it to the closest sewer grate or opening. Then, turn the pump on and lower it into the deepest area of your swimming pool. Depending on the size of your pool and the power of your pump, it may take several hours to drain your pool entirely.

Avoid starting this process if there is heavy rain. The differential pressure between the groundwater and the pool water could cause an inground pool to rise when drained. I wouldn’t recommend acid washing during a scorching hot day either since high heat can damage the plaster.

Step 2: Scrub the Surfaces

Once you’ve successfully drained the pool, remove debris from the bottom of the pool. You can get a jump start on stain removal using an algae brush to remove surface contaminants. Keep surfaces wet by running small amounts of fresh water into the pool. But you don’t want water puddled at the bottom.

Step 3: Prepare the Acid Solution

Follow the manufacturer’s instructions when mixing your acid solution. Always use clean water as your solution base and slowly add muriatic acid. Attempting to add water to the acid could result in chemical boiling, a potential hazardous reaction.

It is also important to use a resin container to hold your mixture. Other materials may weaken after coming into contact with muriatic acid. A leaky container is dangerous, even if you’re wearing protective gear.

Step 4: Scrub and Rinse Surfaces

Keeping your pool’s surfaces wet, go ahead and begin applying the acid solution. Use your acid brush to scrub away stains after waiting about one minute after applying the acid mixture. Keep clean water running on these stains while you scrub. It will most likely take some time, but you should take this opportunity to scrub all of the surfaces of your pool with the acid solution. A thorough job will get the best results and prolong the beauty of your pool.

When you finish scrubbing, go ahead and give all of your surfaces a thorough rinse. Always rinse toward the drain, allowing the wastewater to flow toward the lowest part of your pool.

Step 5: Make the Wastewater Safe

Before you drain the acid-water solution into the sewer, ensure it’s safe. Pouring the acid wash solution into local sewage systems is incredibly dangerous.

Not only could the solution eat through your drainage hose or pump, but it could also cause significant harm to the environment. Adding soda ash as you rinse will neutralize the acid and prevent any unwanted corrosion making it safe to dispose of the water.

For every gallon of acid, sprinkle two pounds of powder soda ash. This ratio should result in a fairly neutral pH.

Step 6: Drain and Refill

After confirming that the remaining wastewater is neutral and safe to dispose of, restart your drainage pumps and hoses. Pour clean water into the pool while draining the wastewater. Doing so can help you remove all traces of the acid before refilling the pool.

When you’re confident that all the dirtied, acidic wastewater has been rinsed from your pool surfaces, shut off your drainage pump and remove the hose from the pool. Then use the garden hose to refill the pool.

As with draining, refilling could take quite a while. Using multiple hoses or water sources could help reduce the time it takes to refill your pool.

Step 7: Balance the Chemical Levels

Once you fill the swimming pool, add sanitizing chemicals to your pool to balance the pH and chlorine levels.

Replace any pumps or valves, and lastly, enjoy your gorgeous, glimmering swimming pool!

Can You Acid Wash a Pool Without Draining It?

Yes, you can! But while you can acid wash a pool without draining the water, this method won’t be as effective as a good old-fashioned drained acid wash. That said, this is certainly a viable solution for pool owners who cannot drain and refill their pools due to any local restrictions.

Acid washing a pool without draining consists of lowering the pH level of the pool until it is acidic and the alkalinity is at zero. In doing so, your acidic water will slowly eat away at the stains and algae.

Step 1: Prep The Pool

Before you start, you will need to thoroughly prep the pool by cleaning and sanitizing it. Shock your pool, scrub it, vacuum it, and over-sanitize it to get it to be as sparkling and blue as possible.

Step 2: Remove All Pool Equipment

The last thing you want is for all your pool equipment to corrode while in the acidic water. So, remove your ladders, rails, pool lights, cleaners, and other accessories that can be affected by the no-drain acid wash.

Step 3: Top Up The Water

Top up the pool water to the very top so that every part of your pool is underwater and can be cleaned by the acid.

Step 4: Shut Off The Pump

Shut off the pool pump and filter, and ensure that it is not turned back on at any point during the process, as the acidic water can damage it.

Step 5: Add a pH Decreaser

Add a pH decreaser or sodium bisulfate to your pool water. Generally, you’ll need around 8 pounds of sodium bisulfate per 5,000 gallons of water. Follow the manufacturer’s instructions to apply it properly to the water.

Step 6: Test The Alkalinity

Test the water and continue adding more pH decreaser until the total alkalinity drops to 0.

Step 7: Brush The Pool and Test The Water

Use a steel pool brush to brush the pool every day for the next 72 hours. And keep testing the water to ensure the pH levels are still low.

Step 8: Raise the pH and Alkalinity

After three full days, reverse the process by adding the pH increaser or soda ash. Add around 8 lbs of soda ash per 5,000 gallons of water, making sure to add the 8 lbs in 3 equal doses over 6 to 12 hours to avoid cloudy pool water.

Step 9: Test The Water

Test the water and make sure your pH level is between the recommended 7.2 to 7.6 and your total alkalinity is between 80-120 ppm. When those levels are reached, turn the pump and filter back on, and enjoy your newly cleaned pool!

Since acid washing without draining the pool is a three-day process, you must ensure no one enters the pool. The acidic water is dangerous and can cause damage to your skin and eyes. If you have pets or small children and plan to acid wash without draining, I highly recommend blocking off the area during the three-day process.

Frequently Asked Questions

How Often Should You Acid Wash Your Pool?

I recommend a minimum of 5 years in between acid washes. Of course, there will be times when you desperately need one earlier. But it is not good for the pool’s surfaces in the long run.

What Kind of Pool Should Be Acid Washed?

You should never acid wash vinyl or above ground pools. The acid will eat away at the lining and can cause holes and leaks. Only use acid to wash inground concrete or gunite pools.

What Are the Risks of Acid Washing Pools?

The risks of acid washing include injuries to yourself and damage to the pool. Improper handling of the acid can lead to chemical burns on the skin, eye damage, and respiratory issues. If the acid sits on your pool’s surface too long, it can discolor or even damage it.

How Much Does It Cost to Acid Wash Your Pool?

Another reason acid washing should only be done when necessary is the high price tag. Draining and refilling your pool and purchasing all necessary equipment can be very costly. The national water cost average is $9 per 1000 gallons. This average does not include the cost of equipment and muriatic acid.

Get My Free Pool Care Checklist

Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.

Something went wrong. Please check your entries and try again.

Bottom Line

Acid washing your pool will refresh the beauty of your pool. It may be hard work and time-consuming, but the benefits make the effort worth it.

Don’t hesitate to call a professional if the task seems too daunting. There is no shame in wanting it done safely and correctly.

No matter which route you decide to take (DIY or getting some help from a pool maintenance crew), you’re bound to enjoy the results of a high-quality, stain-removing acid wash.

Questions about the process? Shoot me a note; I’ll be happy to help.

Scroll to Top