From keeping water balanced and disinfected to stellar cleaning abilities, there’s good reason we use the chemicals we do in and around pools. That said, they should be both used and stored carefully–especially as not all of the chemicals you’ll use are compatible with each other, and mixing them can be highly dangerous and even life-threatening. 

Muriatic acid, a solution of diluted hydrochloric acid, is affordable and highly useful in and around pools. Not only can it be used to lower pH and alkalinity, but it’s a highly effective stain remover, cleaner, brightener, and can even be used to remove calcium buildup and clean salt cells in saltwater pools. It’s also classified as a corrosive, and as a highly reactive liquid acid, must be handled and stored in a specific way to keep staff and pool guests safe. Ahead, we’ll take you through some of the critical specifics to safe, secure muriatic acid storage. 

Handling Muriatic Acid Safely

Pool-grade muriatic acid is corrosive, and highly caustic. Its vapors can cause serious respiratory issues, if not handled while wearing proper protective gear, and it can burn skin within a matter of seconds. Therefore, it’s very important that any staff handling muriatic acid takes proper precautions. That includes wearing acid-resistant gloves, safety goggles, a respirator, and a chemical-resistant apron. Follow the recommendations in the Safety Data Sheets at your facility.  And while you can add it directly to pool water, it’s safest to add it to water in a plastic, chemical-resistant bucket. 

A few other key steps to remember:

• Always add water to the bucket first, not the muriatic acid. Adding the acid first increases your risk of splashback. 
• Ensure you have a hose or water source nearby in case of accidental splashing, and baking soda to neutralize the acid. 
• Thoroughly rinse the bucket after each use.
• Do not use the bucket for any other chemical–doing so increases the risk of dangerous chemical mixing, which could result in explosions, fires, dangerous fumes, and more. Consider color coding your labels to ensure proper chemical separation. 

Keys to Safe Muriatic Acid Storage

The rules for safe muriatic acid storage are not unlike those for most other pool chemicals, with a few key specifics. 

First, as a corrosive, muriatic acid needs to be stored separately from chemicals classified as oxidizers, which includes chemicals that release chlorine:

• Keep muriatic acid in the manufacturer-issued container it came in. This not only helps prevent dangerous mix-ups, but also helps ensure proper ventilation and storage.
• Keep muriatic acid near a hose or other water source in the event a staff member accidentally splashes some on themselves. Whenever mixing it to use, a water source should be close by. Baking soda should also be stored nearby as it can be used to quickly neutralize the acid. 
• Outside of this water source, which should be regularly maintained to protect against leaks, muriatic acid should be kept in a weatherproof location, in an area that is not susceptible to flooding.
• Pool chemicals, including muriatic acid, should be stored in consistent temperatures that stay below 95℉. They should be kept away from direct sunlight, moisture, and humidity. 
• Muriatic acid, like your other pool chemicals, needs to be stored in a well-ventilated area. Any pool chemical storage cabinets should also be well-ventilated, to ensure fumes don’t build-up in the storage room and increase the risk of staff inhaling dangerous vapors. 
• Keep muriatic acid, and all other pool chemicals, far from other facility chemicals, such as gasoline or bleach. 
• Store it away from electrical outlets, heat sources, grills, and any other sparks or open flames. Ensure staff understands the reasons why it is so important not to smoke anywhere near pool chemicals. 
• Never stack chemicals, as this increases the risk of spills. Muriatic acid should be stored off the floor, but not on a high shelf that would be out of reach and increase the risk of spills when staff go to take it off the shelf. 
• Never combine old muriatic acid with new muriatic acid. Don’t reuse containers. 
• Make sure to check OSHA resources, requirements, and recommendations, along with local and state-mandated building and fire codes for safe chemical storage. 

Staff training and education is also critical. The only staff members who should be handling muriatic acid are those who have been properly trained to use it. Educate your other staff members on the dangers of muriatic acid, and other pool chemicals, as well as the importance of safe storage. Post clear signage in chemical storage areas, and keep laminated Safety Data Sheets near each chemical. Ensure staff keeps storage areas clean and clear of debris and trash, including old rags. 

Safely Adding Muriatic acid to Pool Water

When handled and stored safely, muriatic acid is effective and multifunctional around the pool. Another important step to safe use is to ensure you use the proper amount of muriatic acid, and not more than what is needed. When cleaning a cartridge or filter, use a 20:1 water to muriatic acid ratio. When adding to pool water to lower alkalinity and pH, it’s crucial to start with accurate pool water tests in order to determine the specific amount of acid needed. Add the diluted muriatic acid in stages. Dilute in a bucket using a 10:1 water to acid ratio. Turn on the pool pump in order to circulate the acid; leaving it to settle can increase the risk it eats up your pool surfaces. 

Retest water after approximately five hours. Repeat this process until you reach proper pH levels. 

Throughout the process of adding muriatic acid to pool water, accurate test results are crucial, as we mentioned. We designed and built PoolShark H20 to make testing pool water and calculating chemical adjustments, including muriatic acid adjustments, easy. It does the complex math equations for you, ensuring you or staff use the exact, correct amount of chemicals you need–preventing chemical overuse and helping you buy less, spend less, and store less chemicals. When paired with digital LaMotte WaterLink SpinTouch, pool water tests are performed in 60 seconds automatically, and certified to NSF Level 1 accuracy.