If you own a hot tub, you know it's important to maintain the pH, total alkalinity and sanitizer levels (chlorine or bromine). This is the same basic maintenance a pool requires, but a hot tub is smaller than a pool, and the water is hotter, so even with regular maintenance, you need to empty and clean it every three or four months. This is the only way to get rid of debris from sweat and body oils and to clear the water of used sanitizer that has bonded with contaminants. Emptying the tub also gives you a chance to clean the and revitalize the water circulation system.

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Chlorine stabilizers like cyanuric acid can prevent chlorine in hot tubs from destroying the bacteria P. aeruginosa, which causes "hot tub itch."

The Tub Smells Like Chlorine

Whether you use chlorine or bromine to sanitize your hot tub water, you may at some point notice a strong chlorine smell. This means the water has an excess of sanitizer, but it isn't the good kind. The chlorine smell comes from chloramines, compounds formed when free chlorine or bromine ions combine with ammonia or nitrogen. In this form, chlorine or bromine is unavailable for sanitizing, and in large concentrations, chloramines can be harmful. Shocking the water can break up chloramines, but at some point, you need to change the water to get rid of them for good.

Biofilms Must Go

Just as they do in most plumbing systems, biofilms tend to collect on the insides of the pipes in a hot tub circulation system. These biofilms create a barrier of protection from sanitizers such as chlorine and bromine and allow bacteria to grow. Such bacteria could include E. coli_, _legionella and other harmful pathogens. You can clean out these biofilms by adding a line cleaner to the hot tub water before you drain it.

Draining and Cleaning Procedure

It takes about two or three days to thoroughly clean your hot tub, refill it and balance the chemicals. Here's a rundown of the procedure:

Step 1 Flush the Plumbing

Add a line cleaning chemical to the water; remove all the filters; turn on the pump and allow it to circulate. The optimum circulation time depends on the product you use, but it could be anywhere from 45 minutes to overnight. Check the instructions on the container.

Step 2 Drain the Tub

Your hot tub may have a drain that directs the water into your plumbing system, but considering a typical hot tub holds from 500 to 1,000 gallons, you may prefer to direct the water into your garden or onto the lawn. If so, drain the water with a sump pump instead. Be sure to unplug the system or turn off the breakers to ensure the pump doesn't come on while the tub is empty.

Step 3 Clean the Shell

You can wash the tub walls with:

  • a cleaning solution consisting of 1 part vinegar to 4 parts water.
  • denatured alcohol.
  • a solution of 1 ounce of dish soap per gallon of water.
  • a commercial spa cleaner.

Rub down the walls with a sponge or a soft cloth, and avoid the use of abrasive cleaning powders. Be sure to thoroughly wipe the walls dry after cleaning. Any residual cleaner you leave on the walls will make bubbles when you refill the tub.

Step 4 Clean the Filters

Spray the filters down with a commercial filter-cleaning compound. Let them sit for about 15 minutes, then rinse them thoroughly with clean water. Be sure to get all the residual cleaner out or it too will form bubbles when you refill the tub.

Step 5 Refill the Tub

Replace the filters; turn the thermostat all the way to cold, and refill the tub with clean water. It's a good idea to screw a hose filter onto your garden hose before refilling to ensure the water in the tub is free of minerals. Plug in the pump or reset the breaker once the water level has risen above the jets and is at the height recommended by the manufacturer. Turn the thermostat to the desired setting.

Step 6 Balance the Chemicals

Test the water and add chemicals as needed to bring the pH to between 7.4 and 7.6 and the total alkalinity between 80 and 100 ppm. Once this balance has been achieved, shock the water with a commercial shock treatment while the circulation pump is running.

Give It a Day

After shocking the tub, you'll have to wait for the chlorine or bromine concentration to fall to comfortable levels, which is between 1 and 3 ppm. This usually happens in approximately the amount of time it takes the heater to warm the water to the desired temperature -- about 24 hours. So cover the tub; wait for the water to get hot and retest it. When the chlorine levels have fallen below 3 ppm, the tub is ready for soaking.