The best way to ensure that the water in a spa stays clear is to make sure that everyone who uses the spa takes a shower first. If they don't, the only thing preventing the water from turning into "people soup" is the spa filter. The filter is bound to clog up quickly and stop doing its job, which is one reason cleaning spa filters is so important — and there's another.
The water in virtually every household contains mineral salts that leave deposits that are hard to remove. This is scale, which can gum up the spa pump and discolor the lining of the tub. It collects inside the filter media, and it can be difficult to remove.
Vinegar is a weak acid that dissolves scale, and it's safe enough to drink, so cleaning hot tub filters with vinegar is one of the methods recommended by spa maintenance professionals.
Products and Techniques for Cleaning Spa Filters
Treating your spa filter with vinegar isn't the only way to clean it, and depending on the water characteristics, it may not be the best way. Other cleaning agents include:
Household bleach is a disinfectant that is especially effective for killing pathogens introduced by people using the spa as well as algae spores and other harmful microbes.
Soaking your spa filter in laundry detergent will do for the filter what it does for your clothes. Spa pros generally recommend using trisodium phosphate instead of household detergent. TSP is basically regular laundry detergent on steroids, and it's a component in some brands of dishwasher detergent, so some pros advise you to clean the hot tub filter with dishwasher detergent. It's important to rinse thoroughly after cleaning with detergent, or foam could develop in the tub water.
- Muriatic acid: The acid you use to maintain the pH of the spa water can also be used to clean the filter. It dissolves scale and rust stains better than vinegar, but cleaning hot tub filters with muriatic acid is slightly hazardous because of the toxicity and corrosiveness of this chemical.
- Commercial filter cleaner: Commercial filter cleaners are available everywhere in a variety of formulations. Some spa pros exclusively recommend commercial cleaners over household cleaners such as bleach and vinegar.
You can also put your filter in the dishwasher to clean it but only if you have a ceramic filter. A dishwasher generates enough force to damage a paper filter. The more widely recommended general cleaning technique is to hose down the filter, soak it in some kind of cleaning solution and rinse it. It's important to let it dry thoroughly before reinstalling it to finish off any microbes that may still be clinging tenaciously to life.
Get to Know the Filter You're About to Clean
There's nothing complicated about your spa filter, but it's still a good idea to take a minute to get acquainted with it. Filters are cylindrical, and most are the polyester cloth type, but some newer ones such as the Tri-X come equipped with a ceramic media. Both types of filters need regular cleaning.
The parts of a typical filter include:
- The media: This is the part that does the actual filtering. If you have a paper filter, the media consists of the white, pleated polyester paper covering that extends from one end of the filter to the other. A ceramic filter also has a pleated covering that extends from end to end, but the covering is rigid. You can wash this type of filter in the dishwasher.
- The core: This is the rigid inner part of the filter that gives it its structure. It's usually made of plastic, and it's molded into an open cylinder to fit over the water circulation standpipe in the spa's filter compartment. Algae and mold can grow on this part of the filter, so it needs periodic cleaning.
- The end caps: These are also plastic, and they also need to be cleaned. In particular, the rims of the water inlet ports just beyond the path of the water flow can collect debris and harbor algae growth.
You shouldn't use any type of abrasive implement to clean the filter media, but you can use a bottle brush to scrub the inside of the core and the insides of the end-cap rims. Putting a little detergent on the brush helps it remove dirt and algae quickly.
Why Cleaning Hot Tub Filters With Vinegar Is a Good Idea
If you have a hard water problem in your household, a simple experiment can demonstrate the efficacy of vinegar for cleaning mineral deposits. The experiment requires a faucet that has lower-than-normal pressure, which is usually easy to find in a house with hard water. You may have been thinking the low pressure is due to a problem with the pipes or the faucet valve.
Remove the aerator and soak it overnight in a small bowl filled with regular white distilled vinegar. When you replace the aerator in the morning, you'll probably be surprised by the increased flow rate. The vinegar dissolved all the scale in the tiny aerator apertures, and it will do the same for your spa filter. By the way, if the faucet still flows poorly, disassemble it and soak the valve in vinegar.
Vinegar is great for dissolving scale, and it's safer than muriatic acid. It's also an effective disinfectant that is safer than bleach. It's inexpensive, and you probably already have some around the house. What's not to like?
The Procedure for Cleaning Hot Tub Filters With Vinegar
If you decide to clean your spa filter with vinegar, you'll need only a few basic supplies, including a garden hose, a large, flat bucket and a gallon of white distilled vinegar.
Be sure to turn off the hot tub spa before you remove the filter. Leave it off until you replace the filter, or a piece of large debris could get sucked in and gum up the pump.
- Lift the filter off the water circulation standpipe. Be careful not to disturb the standpipe itself, which has a tendency to come off with the filter. You may have to unscrew a threaded cap to release the filter from the standpipe.
- Hose down the filter media to remove large debris, such as leaves and bugs.
- Place the filter in a bucket large enough for it to lay on its side and fill the bucket with enough water to cover it.
- Pour in at least 1/2 gallon of vinegar. Ideally, you want a 50/50 concentration of vinegar and water, so you may have to pour in more than a half gallon of vinegar.
- Let the filter soak for a minimum of 3 hours. It's better if you can leave it overnight, particularly if it has been a while since you last cleaned it.
- Turn the filter over after it has been soaking for about 2 hours to ensure that all parts of it get equal exposure to the cleaning solution.
- Remove the filter from the bucket and rinse it thoroughly with the garden hose. Look for any mineral deposits that haven't dissolved, and if you see any, let the filter soak a while longer.
- Wait for the filter to dry before you reinstall it. It will dry faster if you put it in the sun.
Check the standpipe inlet for any debris that might have floated into it before you replace the filter.
Alternative Ways to Clean a Paper Filter
Soak in dishwasher detergent: Some spa pros say you can clean a hot tub filter with dishwasher detergent. One way to do this is to simply use a cup of dish detergent instead of vinegar in the same amount of water and let the filter soak for 24 hours. If the detergent does not contain TSP, add 4 tablespoons to increase the cleaning power. You can also combine the detergent and TSP with vinegar to create a one-two-three punch that dissolves scale, disinfects and emulsifies oils and dirt particles.
Soak in household bleach: This may be necessary if you haven't had a chance to maintain the spa, and the water has gotten murky. Bleach is one of the best disinfectants. Exposing the filter to bleach repeatedly can damage the plastic parts, though, so you shouldn't use this method frequently. To clean a filter with bleach, cover the filter with 5 gallons of hot water, add 1/4 cup of household bleach and let the filter soak for 2 hours maximum and not overnight.
Use a commercial filter cleaning product: Take the guesswork out of cleaning your spa filter by using a product formulated in a lab. You can find a selection of spa filter cleaners at hardware stores or at spa outlets. If you purchase one of these, use it according to the directions on the container.
Cleaning a Ceramic Filter in the Dishwasher
You can soak a ceramic filter in vinegar, detergent or bleach just as you can a paper filter, or you can also clean it with a commercial filter-cleaning product. Because the filter has a rigid filter media, however, you also have the option to put it in the dishwasher, and that's even easier.
Be sure to empty the dishwasher of all dishes and to set the wash cycle for the longest time possible. Do not add dish detergent and do not enable the dry cycle. After the wash and rinse cycles are completed, remove the filter and let it dry for 24 hours before replacing it.
Cleaning Spa Filters With Muriatic Acid
The muriatic acid you use to maintain the pH of the spa water will also dissolve scale, and it will do it faster than vinegar. However, you might be worried that such a strong acid will damage the filter components. This might be true if you were to use it full strength but not if you dilute it first and limit the exposure time. The recommended concentration is 1:20. That's one part muriatic acid to 20 parts water.
Put on your gloves and goggles because muriatic acid is strong enough to burn your skin and eyes. Fill a large bucket with enough water to cover the filter and then pour in the muriatic acid. Always add acid to water and never the other way around.
Muriatic acid in this concentration will dissolve most mineral deposits in 15 to 20 minutes. After the time has elapsed, turn over the filter to make sure that all sides get the same exposure and wait another 15 minutes before removing the filter and rinsing it off with a hose. Let it dry thoroughly before replacing it.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker.com.