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How to Drain and Clean a Hot Tub

By Matt Giovanisci | Updated: May 29, 2019

In some ways, your spa is like a big bathtub, except you don’t drain it after every use, and you soak in the same water as a bunch of other people. Though maybe you soak in your bathtub with a bunch of other people, too. We’re not judging. The point is, if you don’t already know how to drain a hot tub, it’s time to learn.

Why? Well, so you can properly clean it, a process that is also different from caring for your bathtub. If you’re not sure you know how to clean a hot tub, you’re in the right place. There’s more to it than wiping it down with a cleaning solution. Get it wrong, and you could be in for some nasty surprises.

Eliminating buildup while treating your spa surfaces with care is easier than it sounds, and you don’t need a degree in chemistry to do it. Before you change your hot tub water for the first—or fiftieth—time, learn how to drain and clean your hot tub the right way.

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Why Should You Know How to Drain Your Hot Tub?

Think about it. The same water sits in your hot tub for weeks or months at a time. Sure, you’re treating it with a sanitizer and shocking it on a regular basis (right?), but it’s still the same water, day after day. Eventually, it will need to be changed, regardless of how vigilant you are about water maintenance.

Every time you use your hot tub, organic contaminants are introduced into the water, such as:

That last one doesn’t mean anyone is actually relieving themselves in your hot tub. At least, we desperately hope that’s the case. But every human carries around residue on their bodies, even if they’re careful about, uh, managing those areas. Once they (and you) enter the spa water, that residue does too.

But it doesn’t just stay in the water. Oh, no. It passes through the filter and plumbing too. The filter does its job and grabs most of it, but it can only do so much, especially if it’s a little dirty already. And as those contaminants and bacteria pass through the pipes, they start to build up and create a layer of biofilm, which is as gross as it sounds.

What is Biofilm?

You might’ve thought you already knew how to clean a hot tub. But then biofilm came along and ruined everything.

Bits of bacteria and fungi are trucking down your hot tub’s pipes. They decide it’s nice and cozy in there, and they want to stick around for a while. So that’s what they do—they stick themselves to the interior surface of the plumbing.

But they know their mortal enemy, chlorine, will be along any minute to banish them, so they build a barrier around themselves that’s impervious even to chlorine.

More of their buddies come along and join the party, sticking themselves to the pipes, waving and laughing at chlorine as it goes by. They’re digging in for the long haul until you do something about it.

The longer that biofilm stays stuck to the plumbing, the more contaminants stay in the water, too. Let it build up too long, and it will start to impede water flow and affect filter efficiency as well.

Draining and cleaning your hot tub and using a special plumbing cleaning agent is the only way to get rid of it.

When Should You Do It?

How can you tell it’s time to drain and clean your hot tub? Look for a few clear signs and circumstances.

If any of those conditions apply, it’s time to act.

How Often Should You Do It?

Aside from any specific signs or conditions that tell you your spa needs some attention, it’s a good idea to drain and clean your hot tub quarterly, whether it looks like it needs it or not.

Prevention is always preferable to correction. Keep the biofilm from building up in the first place, and you’re protecting your filter and plumbing system. You’re also maintaining a cleaner, safer soaking environment.

For this reason, it’s always a good idea to keep instructions for how to drain the hot tub nearby to ensure you follow all the steps every time.

How to Drain a Hot Tub

Whoa, not so fast! Don’t pull the plug just yet. You have some work to do before you get rid of the water in your spa.

Flush Those Lines

Even if your sanitizer levels are right on target, your hot tub can develop biofilm. Bacteria feed on it, while also using it as shelter from your sanitizer.

That same bacteria ends up in your water, eating up chlorine and exposing you and other bathers to contaminants, such as Legionella, which causes Legionnaires’ Disease, Staphylococcus aureus, which commonly causes hot tub folliculitis, and E. coli, which can cause intense gastrointestinal distress.

When this goo forms inside your lines, it can’t be removed through normal spa water circulation, filtration, or even by adding more sanitizer or shock.

So before you drain and clean your hot tub, add a plumbing cleaner, also called a line flush product. This special cleaner is specially formulated to break down biofilm. Follow the package directions to ensure you use the right amount for your hot tub’s volume. Once you’ve added it, let it circulate for a minimum of 20 minutes.

But if this isn’t your first time cleaning your spa, but you haven’t been using a hot tub line flush, or if the hot tub has been sitting unused for quite some time, you can—and really should—let the plumbing cleaner circulate for a few hours, or even overnight.

Plumbing cleaner may cause gross-looking foam to form on the surface of the water as it circulates through your spa. That just means it’s working and pulling all that nasty biofilm out of the pipes. You’ll be draining and cleaning your hot tub next anyway, so don’t worry about the foam.

The Power of Gravity

The lowest-cost option for draining your hot tub is to connect a hose to the spa drain and allow gravity to work its magic. This is also the most time-consuming choice, usually taking hours to completely empty your spa. But that doesn’t have to be a bad thing.

It actually gives you time to move your hose so drained water doesn’t pool in one area, which you might want to do if you’ll be draining your spa water into your yard or garden.

Important: Before you drain your spa, flip the hot tub breaker to cut all power and eliminate risk of electrical shock.

The Power of … Power

Maybe you’re in a hurry, or you just don’t have the patience to wait on gravity. No problem. You can use a sump pump to empty your hot tub in minutes rather than hours. Open your spa drains at the same time, and empty the tub even more quickly.

Because a sump pump will drain the hot tub quickly, plan to stay nearby to keep an eye on the water level. If the pump continues to run once the water is gone, it can burn up the motor, so turn off the pump as soon as it stops pumping water.

Some pumps will get the water down to a fraction of an inch, while others will need to be shut off with a few inches of water remaining. Your hot tub drains will take care of the rest.

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Where To Drain Hot Tub Water

A lot of cities have laws that require you to drain your hot tub water into the sewer system. Those cities typically provide sewer access through a special drain somewhere on your property.

This is not to be confused with a storm drain, where you should never dispose of hot tub water because those drains lead to natural bodies of water. Drained spa water can harm fish and other wildlife.

If you don’t have direct sewer access, you can run a hose into the drain in a utility sink in your home, or water your lawn or gardens with the old spa water, provided you’ve allowed chemical levels to dissipate. Plants don’t exactly thrive on chlorine.

Important: Before you drain your hot tub, check your city’s ordinances to ensure you’re adhering to the law, and preventing any damage to the environment.

How to Clean a Hot Tub

Now that your hot tub is empty, you’re halfway to the finish line. Get ready to expend a little elbow grease. Just don’t get that grease in your spa. Ew.

Clean or Replace the Filter

While the water is draining from your spa, you have plenty of time to clean your filter. A special filter cleaning spray is good for this job.

Better yet, take a little more time and deep clean the filter. Grab a 5-gallon (20-litre) bucket, and fill it nearly to the brim with water. Add the dose of hot tub filter soak indicated in the product instructions, give the water a swish to dilute the cleaner, and submerge the filter. Leave it to soak for 24 hours.

If you remove the filter, and it’s so dirty no amount of cleaner is going to make a difference, first, replace it. Second, clean your filter more often!

Important: Anytime you clean your filter with a cleaning product, be sure to rinse the filter thoroughly with clean water before placing it back in your hot tub. Any residual cleaner might cause foaming when you restart your spa, and then you’ll have to start this entire process over again.

Clean the Spa Shell

Once it’s empty and you’ve removed the sump pump, your spa is ready for surface cleaning.

Tip: Between quarterly draining and cleaning, you can clean the portion of the shell that’s above the water line. Any cleaner you use may end up in the water, so we recommend using a melamine sponge (also called a Magic Eraser).

How to Refill a Hot Tub

Ah, look at that squeaky clean hot tub! It’s so pretty, you almost don’t want to fill it back up, right? But it’s no fun to sit in an empty spa, so close the drains, and break out that hose.

Important: Before you start adding fresh water, double check to ensure the breaker is still off. Better safe than sorry.

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Tip: When refilling your hot tub, use a hose filter to reduce impurities such as calcium and copper that may affect your water chemistry and overall spa health. You’ll start out with higher-quality water in your spa and reduce the risk of staining and mineral deposit buildup.

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Set aside some time for refilling the spa. You don’t want to leave it unattended and end up with a flooding situation, especially if your hot tub is indoors.

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07/20/2021 06:02 pm GMT

While You’re At It …

As you wait for your hot tub to drain and refill, you can take on a few other tasks to get a fully clean hot tub.

Clean the Spa Cover

If you’re using a hot tub cover, now is the perfect time to clean that, too. If your spa resides outside, you may also want to apply a protectant to the cover to help avoid sun damage.

And if you’re not using a cover, you’re losing money in water, chemicals, and energy costs via evaporation, so get a cover!

Clean the Spa Cabinet

Don’t get so focused on the inside of the hot tub that you forget the outside! Your spa cabinet puts up with a lot of abuse in the form of splashout, humidity, and sun if it’s outside. Take some time to care for it, and it’ll last a lot longer.

Depending on what your cabinet is made from, clean it with an appropriate product. Most cabinets are made from wood, so use a gentle wood cleaner and a soft cloth.

Apply a wood protectant as well, whether your hot tub is indoors or out. And if it’s outside, use a protectant with a UV shield.

Worry-Free Soaking

Now that you know both how to drain your hot tub and how to clean your hot tub, there’s no excuse to let your spa descend into swamp territory. Keep the water balanced, test it regularly, and keep your filter clean, and you should only have to do a full drain and clean every quarter.

In the meantime, you can relax and enjoy your squeaky clean tub full of sparkling, clear, biofilm-free water.

Happy Soaking!

Matt Giovanisci is the founder of Swim University® and has been in the pool and spa industry since 1995. Since then, his mission is to make pool and hot tub care easy for everyone. And each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.
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