How to Drain a Hot Tub



A hot tub is a great addition to a backyard sanctuary and tons of fun for family and friends to enjoy. Since it’s smaller and involves heated water, there are a few differences between pool and hot tub maintenance. One of these is periodically draining and refilling — something you don’t have to do with your swimming pool.

If you own a hot tub, you’ve probably heard that this is something you should do. But how does it work? How often do you need to do it? Why? Don’t worry, we got you covered. Whether you’re a hot tub newbie or veteran, get ready to learn the right way to go about this essential part of hot tub care.

Why Should You Drain Your Hot Tub?

You might be thinking, “I chlorinate, balance, and check my spa water chemistry all the time. The levels are perfect and the water looks great! So, why do I need to drain my hot tub water?”

If you’re lucky enough to have both a pool and a hot tub in your backyard (congrats, by the way) you may think that pool maintenance and hot tub maintenance are the same things. Sure, there’s more water in your pool but that just means you just need to balance your water chemistry on a smaller scale for a hot tub… right? 

Well, not so much. Hot tubs are a different beast than backyard swimming pools mainly because of the temperature at which they operate. Hot water can be a breeding ground for bacteria, germs, and other gross things like E. coli, legionella, and Pseudomonas aeruginosa, the bacteria that causes hot tub rash.

Whenever you use your hot tub, you and your buddies are bringing in all kinds of new contaminants without even realizing it. Things like hair products, makeup, lotions, body oil, sunscreen, and sweat are all stewing in your hot tub now. Gross.

Your filter is going to be cleaning a lot of this gunk out of the water but, as it’s all picked up and moved through the pipes, it actually starts to build up and create a layer of a nasty substance called biofilm. 

What is Biofilm?

No, unfortunately, it’s not a biographic motion picture… that would be way more fun. For our purposes, Biofilm is a devious mass of bacteria, algae, protozoa, and viruses that has even been described as a “city for microbes”.

All of these sneaky invaders are flowing through your hot tub plumbing, sticking themselves to the pipe walls, and making themselves right at home. That means all the filtered water that flows by them could be getting recontaminated. What’s worse is that they’ve even learned how to build a protective layer around themselves to defend against chlorine! Body armor… seriously?

And the bad news doesn’t stop there. The absolute worst part about biofilm is that it is a major cause of waterborne diseases and infections. Apart from being a cool “meeting place” for microorganisms to go hang out and exchange phone numbers, researchers have estimated that 60-80% of microbial infections in the body are caused by bacteria growing as a biofilm.

Biofilm can form in any watery areas since it needs moisture to grow. This means your hot tub is ground zero for your battle against biofilms. They can even form on your teeth! So just as you brush and floss for good dental hygiene, you need to do the same for your hot tub.

When It’s Time to Drain

All of this talk about biofilm and bacteria may have grossed you out… sorry about that. It also may have motivated you to go drain your hot tub right now! Well, you can if you want. But it might be easier just to check for some unmistakable signs that it’s time to drain.

  • You’ve recently had a big party with lots of guests in and out of your hot tub.
  • You’ve been trying everything but just can’t seem to get the water to clear up.
  • You haven’t used your hot tub in months.
  • You’ve been using your hot tub a lot more than usual.
  • Your hot tub is starting to smell… bad.

These are very obvious signs that it’s time to drain your hot tub but hopefully you’re testing the water frequently and discover the problem before it gets to this point. Just remember to follow these easy recommendations from the CDC when testing your hot tub:

  • Hot Tubs: free chlorine (2–4 ppm) or bromine (4–6 ppm).
  • Both hot tubs and pools should have a pH level of 7.2–7.8.

It’s a good idea to drain and refill your hot tub every 3-4 months unless you notice one of the above signs going on. In that case… sooner. With proper maintenance, you can keep your hot tub clean in the meantime and not have to drain more often than that.

How to Properly Drain Your Hot Tub

And before you ask… yes, there is a right way and a wrong way to drain your hot tub. Today, we’re going to talk about the right way and walk you through it step-by-step. Before you jump right in and pull out the plug, your first step is to flush out the dirty lines.

Step 1: Flush the Lines

Remember the gross biofilm we just talked about? Yep, that is just sitting in your lines, mocking your chlorine’s attempt to clean the water, and clogging the water flow. 

Even when you’ve tested your water and everything seems like it’s on-target, there still may be biofilm lurking there. This stuff is nasty and can’t be removed by your filter, extra chlorine, or even shock. That’s why this is our first stop on the clean hot tub express.

You’ll need to get a special product for this step. It’s called plumbing cleaner or line flush and is made specifically to de-gunk your lines and clear out any biofilm that’s hiding in there. Make sure to follow the manufacturer’s instructions when determining how much to add. Then, sit back and let it circulate for at least 20 minutes.

Don’t worry if you notice some brownish foam floating on the surface. That just means the line flush did its job! You’re draining the hot tub water anyway, so it’s no big deal.

Step 2: Turn Off the Power

There’s nothing more dangerous than mixing electricity with water. It can also cause damage to your hot tub if it runs without any water in it. Make sure everything is unplugged and switched off before you start draining.

Step 3: Drain the Hot Tub

Your hot tub manufacturer will have some specific instructions for you here. Make sure to follow those carefully before proceeding. You’ll need to start by finding the drain plug and pulling that out to allow water to escape. Here, you have some options:

  • Gravity: You can connect a drainage hose to the spa drain and let your good friend gravity do the rest. Although draining your hot tub this way takes hours, this is the cheapest option and also gives you some time to move onto step 4.
  • Sump Pump: If you don’t have time for that noise, maybe you have a sump pump on-hand. Make sure to open up the spa drain at the same time to speed things up. Just don’t wander away when using this method. If your pool is empty and the pump keeps pumping, it’s going to burn out the motor. So be sure to keep an eye on the water levels and turn it off as soon as it stops pumping water.

Pro Tip: Make sure you know your city’s rules about where you’re allowed to dispose of your hot tub water. Never dispose of spa water into a storm drain to avoid environmental damage.

Step 4: Clean (or Replace) the Filters

If you’re still waiting for your hot tub to drain, now is a good time to remove the filters and clean them up a bit. 

Start by spraying them down with a good spa cleaner and hosing them off. If they are really dirty, they may need a soak. You can also use specially-made filter soak products for this, or just mix vinegar and water in a bucket.

Remember that if you’re using any cleaning products on your filters you need to make extra sure to rinse them thoroughly before putting them back in. Excess cleaning product will cause your hot tub to foam up and you’ll have to start all over again.

If you’re unable to get them clean, I hate to tell you, it may be time to replace. A good rule of thumb is to replace your filters once a year. So if it’s been that long or they’re beyond hope… the time has come.

How to Clean Your Hot Tub

Hang on, we’re almost there! Now that you’ve flushed, drained, and cleaned your filters, it’s time to clean the hot tub itself.

Step 5: Clean the Hot Tub Shell

After all of the old water has drained, grab your handy bottle of hot tub cleaner and spray the whole thing down. Next, wipe it down with a towel until all of the cleaning solution is gone. 

Just to be on the safe side, rinse the interior out with a hose and wipe down again with a fresh towel. If there is any cleaning solution left when you refill the hot tub, it’s going to look like a bubble bath… but with cleaning chemicals. You don’t want that.

How to Refill Your Hot Tub

Wow, we’re almost there! I know you need a relaxing soak soon, so we’re gonna get through this. Luckily, the next step is pretty easy.

Step 6: Refill the Hot Tub

You probably still have your manufacturer’s instructions handy, so take a quick peek at those before getting started. Your model of spa might have some specific guidelines. Otherwise, just fill it up with your backyard garden hose.

If you have a hose filter, you should definitely use it. It will take out a lot of minerals and metals in the local water that can affect your spa chemistry. Make sure to plug the spa drain back in and turn on that hose.

Wait, don’t walk away! This is not the time to go do other things. Accidentally overfilling can cause serious problems when you turn your spa back on so it’s best to stick around and keep an eye on it. If you happen to fill it up too high, make sure to remove any excess water immediately (before you turn it on).

Step 7: Turn on the Power and Balance Your Chemicals

Once your hot tub is refilled to the proper level, it’s time to turn it on and get the fresh water circulating. Add your usual start-up chemicals too, so they have time to work before you decide to hop in.

Test the water to check on pH and alkalinity levels and then shock the hot tub with your shock of choice (chlorine or bromine). After these steps are completed, it’s important to keep your hot tub covered for 24 hours. 

During this time, allow the water to heat up to between 80°F (27°C) and 104°F (40°C) before balancing the chemistry again. Congratulations, you’re all done! Now you’re ready for a relaxing and worry-free dip in your sparkling clean hot tub.


That wasn’t so bad, was it? Now that you’re hot tub savvy it will be super easy to keep your spa clean and fresh all year long. Testing regularly, keeping an eye on your water chemistry, and draining 4 times a year is all it takes to have a gorgeous and healthy hot tub.

Follow these simple guidelines and you’ll have more time to relax and enjoy all the benefits of your beautiful backyard bathing oasis.

Categories: Hot Tub Care, Hot Tub Maintenance