How to Drain and Clean a Hot Tub (and How Often to Do It)

Last updated: September 2026

Keeping your hot tub clean and germ-free is an important part of owning one. In this article I’ll teach you exactly how to drain and clean your hot tub, along with the tips I’ve picked up over the years.

Why drain and clean your hot tub?

Hot tub water doesn’t last forever. Over time, non-organic contaminants like sunscreen, lotion and the salts from sweat build up. These are total dissolved solids (TDS), and they make the water cloudy, use up your sanitiser and cause chemical imbalances. The UK HSE’s spa guidance says TDS shouldn’t be more than 1,000 mg/l above your fill water. A regular drain, clean and refill also gives you a chance to clean the shell and the fronts of the jets.

A sensible rhythm for a home tub is every three to four months. To be more precise, use the formula: gallons in the tub, divided by the number of regular bathers, divided by 3 = the number of days between changes. That’s the same formula I use in my beginner’s guide to hot tub maintenance. Whether you’re preparing for winter or just flushing the system in summer, it’s worth knowing how to do it properly. If it’s for winter, see winterizing your hot tub.

Steps to draining and cleaning your hot tub

1. Turn off the power

First, turn off the breaker (or isolator) for the tub. You don’t want it trying to heat, filter or pump with no water in it. Don’t turn it back on until the tub is refilled to its normal level.

2. Drain the water

The quickest way is a submersible pump. Otherwise, a garden hose works well. For a gravity drain:

1. Take off the front panel of your hot tub and find the drain valve or hose connector.
2. Attach a hose and run it to a suitable place. Avoid flooding your yard or a neighbour’s. Chlorinated or brominated water shouldn’t go to storm drains or watercourses, so check your local rules. Letting the sanitiser fall to a low level first, or using a neutraliser, helps.
3. Open the valve and let it drain. It’s slower than a pump but works just as well.

Once the hose has drained as much as it can, use a mop or wet/dry vacuum to get the rest out of the bottom of the tub. The goal is to make the tub as dry as possible so you can clean it properly.

3. Clean the shell

Now’s the perfect time to clean the shell. Use a soft cloth or sponge and a spa-safe cleaner to lift dirt and mildew. Don’t forget the jets and small crevices, where buildup hides. If you want a natural option, baking soda paste works well on stubborn marks (see how to clean your hot tub with baking soda). Rinse everything thoroughly, because leftover cleaner will foam when you refill.

A surface wax or polish made for hot tubs can add a protective shine. Check that it’s suitable for your shell first. If there’s biofilm in the pipes, run a spa line flush before you drain.

4. Look after the filters

While the tub is off, this is a stress-free time to give the filters a good soak and clean. Consider replacing them once a year. My guide to cleaning a hot tub filter cartridge has the full method.

5. Do the extras

It’s also a good chance to condition the cover (see hot tub cover maintenance), rinse down the cabinet with a hose, and check the inside of the cabinet and the base for leaks (see how to find and fix a hot tub leak).

6. Refill and rebalance

Close the drain valve tightly and refill. Run the hose for a few minutes first to flush out any debris, and fill through the filter compartment to help avoid air locks (see how to fill a hot tub the correct way and air lock in a hot tub). Then switch the power back on and balance the water in order:

Step	Target
Total alkalinity	80 to 120 ppm
pH	7.2 to 7.6
Calcium hardness	150 to 250 ppm
Free chlorine or bromine	Free chlorine 3 to 5 ppm, or bromine 4 to 6 ppm
Cyanuric acid (CYA)	As low as possible. A fresh fill resets it

Full detail is in my chemical balancing guide.

Choosing cleaners: the natural way

Before you reach for the kitchen cupboard, it helps to know how the different types of cleaner behave. You wouldn’t use bleach on a sensitive surface, just like you wouldn’t use olive oil to clean your toilet. Let’s not even imagine that disaster.

• Detergents: break down sticky stains by emulsifying oils (dish soap, laundry detergent). Avoid these on a hot tub, because they cause foam.
• Acids: tackle rust and hard water stains (limescale removers, vinegar). Use them dilute and rinse well.
• Sanitisers: disinfect and kill bacteria (bleach). Never mix them with acids, including vinegar.
• Bases: cut through grease and grime (typical all-purpose cleaners). They can leave residues, so I’d stick to spa-safe products.
• Abrasives: scrub tough marks but scratch delicate surfaces (steel wool, scouring powder). Keep them away from your shell.

How often should you clean a hot tub?

How often	What to do
Every 3 to 4 days	Check the water for cloudiness or film, and test pH, alkalinity and your sanitiser. Leave at least two hours between chemical adjustments.
Once a month	Clean the filter (with two filters you can alternate them), and clean the cover.
Every 3 to 4 months	Drain, clean the shell and jets, refill and rebalance. Sooner if it’s heavily used.
Once a year	Replace the filters, and consider a professional check of the equipment.

Stick to that and your tub will stay clean, efficient and ready to use for years. If the water is misbehaving between changes, see cloudy water in a hot tub and foam in a hot tub.

Parts and cleaning supplies

For filters, spares and hot tub care products, see parts4tubs.co.uk (UK) or parts4tubs.com (USA). Building your own tub? Have a look at my hot tub plans.

FAQs

How often should I drain my hot tub?

Every three to four months for a typical home tub. Use the formula (gallons divided by regular bathers, divided by 3) for the number of days between changes.

How long does it take to drain a hot tub?

With a submersible pump, usually under an hour. With a hose and gravity, it can take several hours.

Can I use household cleaner in my hot tub?

I wouldn’t. Detergents, fragrances and oils leave residues that cause foam and upset the chemistry. Use a spa-safe cleaner, or baking soda paste for stubborn marks, and rinse well.

Where can I drain hot tub water?

Check your local rules. Don’t drain chlorinated or brominated water into storm drains or watercourses. Let the sanitiser fall first, or use a neutraliser.

How do I stop air locks when I refill?

Fill through the filter compartment or skimmer so the water pushes air out of the plumbing, rather than trapping it.

Got a question about your own tub? Drop it in the comments below. I read them all.

Cheers,
Andi

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Thanks - Andi

 

Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Fast forward to 2025, I've helped over 1400+ DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi