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How to Drain and Clean a Hot Tub

You should drain and clean your hot tub every 3 to 4 months. Depending on how frequently you use the tub, you’ll need to change the water at varying times. This is a relatively simple task even if you don’t have a lot of free time.

How to Drain and Clean a Hot Tub

Think of your spa as a large bath tub. Bath tubs need to be drained and we know why: chemical build-up, body oils, and just general “funk” can accumulate in your hot tub water.

Keeping water in your hot tub longer than 3-4 months, regardless of how clear it looks and what the specialty products you add, exposes you to unhealthy and unnecessary amounts of harmful chemicals.

The most harmful chemical being USED sanitizers in your water. Whenever chlorine or bromine comes in contact a piece of ammonia or nitrogen, it changes into a stable form of sanitizer that is no longer able to kill bacteria. These used “pieces” of sanitizer are called chloramines and are the source of chemical smell from your water.

Removing Biofilms in Your Hot Tub Plumbing

Before you drain the hot tub, you must run a line flush product through the tub. The vast majority of bacteria lives inside the plumbing lines under a layer of sticky tar like substance called biofilm.

This biofilm is both a food source as well as a layer of mechanical protection that prevents the chemical sanitizers in your system from reaching the bacteria. Biofilm sticks to the surfaces of your hot tub that comes in contact with water. And they cover themselves with a layer of slime that protects them from sanitizers such as bromine and chlorine.

These bacteria can even be harmful. Some biofilms can contain:

  • Legionella
  • Pseudomonas Aeruginosas
  • Mycobacterium Fortuitum
  • E-Coli

If you simply drain and fill the tub then you will transfer almost all of the old bacteria directly into the new water. This persistent biofilm can cause bacterial blooms that can leave you red and itchy, or with folliculitis in more severe cases.

How to Drain Your Hot Tub and Remove Biofilms

1. Add a Line Flush Product To The Hot Tub Water

The line flush product is added to the old water circulated for a least 20 minutes and up to 4 hours depending on the product direction. NOTE: It’s not uncommon to develop a 4″ thick layer of brown/black foam covering the surface of the water as the long established bacteria pull away from the plumbing lines.

2. Remove The Filters and Turn Off The Power to Your Hot Tub

First, remove the filter(s) from the filter well. You can start cleaning the filters while the hot tub is draining.

Disconnect ANYTHING electrical running to your hot tub before you begin. You don’t want the hot tub turning on when there’s no water in it. That would be bad for the pumps and heater in your tub. Make sure the breaker is tripped and the power is disconnected.

NOTE: If you’re not comfortable with the electrical systems of your hot tub, or even a little unsure, please call a licensed electrician or hot tub technician to help.

3. Start Draining The Hot Tub

Use a sump pump or the drain plug on your hot tub, and drain the hot tub leaving only the foot well full of water.  I highly recommend using a sump pump because it will be much faster than draining with just the drain plug.

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How To Clean Your Filters While the Hot Tub is Draining

Every hot tub is installed with a number of filters which ensure your water is clean and safe. The filters remove any debris and other substances from your water. Depending on how often you use it, and where your tub is located, depends on how often your filters will need replacing.

If you have backup replacement filter cartridges, I recommend soaking the filters for 24 hours using a diluted hot tub filter cleaner (according to the directions on the bottle). Make sure you use enough water to completely submerge one filter. If you have room, you can add more filters to the solution.

If you DON’T have backup replacement filter cartridges, generously spray down your hot tub filters with a hot tub filter cleaner and let them sit for about 15 minutes. Then, rinse them down with clean water.

  • You can also use any spa filter cleaner that’s sold at your local hot tub store, which is highly recommended. If not, you can dilute one part muriatic acid to three parts water.
  • Make sure you rinse your filters with water thoroughly after cleaning. Otherwise, it may cause foam in your hot tub.
  • Your local pool or hot tub supply store may offer a filter cleaning service if you don’t want to do it yourself.

How to Clean Your Hot Tub Once It’s Drained

Once the water is removed from the hot tub you can wipe the interior surface with four parts water to one part white vinegar to clean the surfaces. Although, I recommend buying a hot tub cleaner.

Spray down the inside of your hot tub and wipe it clean. Make sure not to leave any cleaner inside the tub. It could cause your water to foam.

How to Clean The Inside Shell of a Hot Tub

Knowing how to clean the inside shell of a hot tub is key to making sure your hot tub is clean and ready when you want to enjoy the warm, soothing water.

Refill Your Hot Tub with Fresh Water

Now that the old water has been removed and your hot tub shell is clean, it is time to refill it with fresh water. To do that, I recommend a hose filter that fits on the end of your garden hose.

These filters remove impurities such as copper, iron, and calcium that could be present in your tap water. They also cause hard water and damage your hot tub. There are ways to reduce these impurities after it’s been filled, but it’s easier to remove them you refill your hot tub.

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Filling Your Hot Tub Using a Hose Filter

  1. Attach your hose filter to the end of your garden hose.
  2. Check all the drains on the hot tub to be sure they are closed.
  3. Double check that there is still no power to the hot tub.
  4. Turn on your hose and fill your hot tub to the optimal level as set by your hot tub manufacturer.
  5. Restore power to your hot tub and turn it on allowing the jets to run. If you need to prime your hot tub, do so now.

Start Your Hot Tub and Add Chemicals

  1. Test your water and adjust your pH levels to between 7.4 and 7.6, your Total Alkalinity (TA) levels to 80 ppm and your Calcium Hardness (CH) to 100 ppm.
  2. Shock your fresh hot tub water while the hot tub is running and allow it to continue to circulate .
  3. Adjust your temperature, if necessary, to between 100 degrees and 104 degrees Fahrenheit.
  4. Replace your cover and allow the spa to run for 24 hours to heat properly.
  5. After a day has passed, run the clean cycle on your hot tub and then check your pH levels, TA levels, and CH levels again.

If you perform this maintenance task on your hot tub right before the weather turns cold and again early in the spring then you will minimize your workload while protecting your health at the same time.

Stop Biofilms From Returning

Maintaining high water quality is key to prevent biofilm. There are enzyme based products, such as the one below, that’ll do the trick. Simply add the enzyme to your water weekly or monthly. This will break down the oils and other contaminants that allow biofilms to grow.

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Even with these treatments, you should use a line flush product at least once a year as part of your regular maintenance. And your filters should be soaked in a cleaning solution at least three times a year to prevent biofilms from coming back.

Look Out for Limescale

Limescale can coat your hot tub both on the shell and even the plumbing, giving biofilms yet another place to hide and even reducing the efficiency of your hot tub in the process. If you have limescale buildup, then you will need to flush your system completely and change the water.

Once that is done, you need to pay close attention to your pH levels and even consider adding a limescale prevention chemical in the mix of your water.

Congratulations! You Drained and Cleaned Your Hot Tub Properly

Who doesn’t want clean and safe water in their hot tub? Draining and cleaning your hot tub every 3-4 months is the key.

Also, get your limescale buildup and biofilm growth under control before it becomes a major problem. Allowing these to grow can lead to poor hot tub function and bad water quality that could even be dangerous.

So start testing that water today and take the steps necessary to get rid of that limescale buildup and biofilms in your hot tub. Your bathers will thank you.

Happy Soaking!

Thanks to Steve Goodale from Green Pools in Burlington Ontario Canada. Photo Credits: DaveParkerAudinCogDog

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Last Updated: Sunday, July 28th, 2013