Owning a hot tub is one of life’s great pleasures. There’s nothing quite like sinking into warm, bubbling water after a long day. But just like a swimming pool or even a fish tank, the water in your hot tub doesn’t stay fresh forever. Over time, it picks up body oils, lotions, sweat, and all sorts of invisible buildup that chemicals alone can’t keep up with. That’s why every hot tub owner eventually needs to drain the old water out and start fresh.
If you’re new to hot tub ownership, don’t worry: it’s simpler than it sounds. Let’s walk through how to tell when it’s time for a water change, how to actually do it, and some easy habits that’ll make the whole process less frequent.
How Often Should You Change the Water?
There’s no single answer that works for everyone, because it depends on how much you use your tub and how many people are soaking in it. But there is a handy rule of thumb that gives you a solid starting point: take your hot tub’s water capacity in gallons (you’ll find this in your owner’s manual), divide it by the average number of people who use it each day, and then divide that number by three. The result is roughly how many days you can go before the water needs changing.
So for example, if your tub holds 300 gallons and two people use it daily, that’s 300 ÷ 2 ÷ 3 = 50 days, or roughly every seven weeks. It’s not an exact science, but it beats guessing.
How Do You Know It’s Time?
Even with a rough schedule in mind, your hot tub will give you plenty of signals when the water is ready to be replaced. Learning to read those signals is one of the most useful things you can do as a new owner.
Test the water regularly. You can pick up simple test strips at any pool supply store. Just dip one in the water and it’ll tell you where things stand. You’re mainly looking at three things: the pH (which measures how acidic or basic the water is), the alkalinity (which helps keep the pH stable), and the sanitizer level (that’s your chlorine or bromine or the stuff that kills bacteria). If you find yourself constantly fighting to get these numbers right, and nothing seems to work no matter what you add, the water has probably reached the end of its useful life.
Trust your eyes and nose. Healthy hot tub water should look crystal clear. If it starts looking cloudy, has a greenish or yellowish tint, or you can see little bits floating around even though the filter is running, that’s a red flag. Same goes for smell – if you catch a funky or chemical-heavy odor coming off the water, it’s telling you something.
Watch for foam that won’t go away. A little bit of bubbling from the jets is totally normal, but if you’re seeing a thick, frothy layer of foam sitting on top of the water, that usually means there’s a buildup of soaps, lotions, or body oils that the sanitizer can’t handle anymore.
Look for crusty white buildup. Over time, minerals like calcium that are naturally present in your tap water can leave behind a rough, chalky residue on the walls and around the jets. This is called scaling, and while you can scrub it off, if it keeps coming back aggressively, a fresh fill of water will help reset things.
Consider the season. In the summer heat, water evaporates faster and chemicals burn off more quickly, which means you might need to change the water more often. In the winter, things tend to stay more stable, so you can usually go a bit longer between changes.
Check your owner’s manual. Your hot tub’s manufacturer will usually give you a recommended schedule. Many suggest every three to four months as a general rule, though this varies depending on the model.
How to Actually Drain and Refill It
When the time comes, here’s how to handle it without any headaches.
First, turn everything off and unplug it. You never want the pumps or heater running while there’s no water in the tub. Most hot tubs have a dedicated breaker so please flip that off before you start.
Drain the water. The easiest way is with a small submersible pump, which you can find at any hardware store for around twenty to forty dollars. You just drop it into the tub, attach a garden hose to the outlet, point the hose wherever you want the water to go (like your lawn or a storm drain, if your local rules allow it), and turn it on. It’ll empty the tub in under an hour. If you don’t have a pump, many hot tubs have a built-in drain valve near the bottom. Just attach a hose, open the valve, and let gravity do the work, though this method is slower.
Give it a good scrub while it’s empty. This is your chance to clean the inside of the shell, wipe down the jets, and pull out the filters for a rinse or replacement. A non-abrasive sponge and a hot tub-specific cleaner work best but please avoid household cleaners, which can leave behind residue that’ll foam up when you refill.
Use a pre-filter on your hose when you refill. This is a small, inexpensive filter that screws right onto your garden hose and catches a lot of the minerals and impurities in your tap water before they ever reach the tub. If you have hard water (water with a high mineral content), a pre-filter makes a noticeable difference. It cuts down on scaling and makes balancing the chemistry much easier right from the start.
Fill it back up with your garden hose. It’s a good idea to place the hose directly into the filter area (sometimes called the filter well) so that water flows through the plumbing from the start, which helps prevent air pockets that can cause issues with your pumps.
Balance the chemistry before you hop in. Once the tub is full and running, test the water and adjust the pH, alkalinity, and sanitizer levels. Let the water circulate for a few hours so everything mixes thoroughly. Then you’re good to go.
Simple Habits That Keep Your Water Fresher, Longer
You’d be surprised how much a few easy routines can extend the life of your water and push that next drain-and-refill further down the calendar.
Shower before you soak. This is the single simplest thing you can do, and most new owners never think about it. A quick rinse before getting in washes off lotions, deodorant, hair products, and sweat (all the stuff that gunks up the water fastest). You don’t need a full shower, just a quick one-minute rinse makes a real difference.
Keep your filters clean. Think of your filter as the lungs of your hot tub. If it’s clogged up, everything works harder and less effectively. Get in the habit of pulling it out and giving it a rinse with the garden hose every couple of weeks, and once a month do a deeper clean by soaking it overnight in a filter-cleaning solution. Most filters also need to be fully replaced once or twice a year.
Always keep the cover on when you’re not using it. A good-fitting cover does much more than hold in heat. It keeps out leaves, dust, pollen, insects, and rainwater – all things that throw off your water chemistry and make the sanitizer work overtime. It also slows evaporation, which means you’re not constantly topping off the tub and adding more tap water minerals into the mix.
A Few Extra Tips Worth Knowing
If you’re environmentally minded, you can reuse the drained water on your garden or lawn – just make sure you’ve let the chlorine or bromine dissipate first by letting the water sit for a day or two without adding chemicals before you drain it.
If you live somewhere with water restrictions or drought rules, check with your local water authority before draining. Some areas have specific guidelines about when and where you can drain large volumes of water.
And if you’re in a cold climate, be careful about draining your tub in the middle of winter. Any water left sitting in the plumbing can freeze and crack the pipes. If you’re shutting it down for the season, look up how to properly winterize your specific model. Your owner’s manual will walk you through it.
Taking care of your hot tub water might sound like a lot at first, but once you get into a routine, it becomes second nature. A little regular attention keeps the water clean, your equipment happy, and your soaking sessions as relaxing as they should be.