Draining a hot tub is mostly waiting. The parts that go wrong are at the beginning and the end: draining with the power still on, and refilling into a pump that then won't move water.
Before you start
- Time
- 3 hr
- Difficulty
- Easy
- Cost
- Purge product and a filter, under $50
Tools
- Garden hose
- Submersible pump (optional)
Supplies
- Your maker's shell cleaner
- Clean or new filter cartridge
- Line purge product (optional)
Key takeaways
- Power off at the breaker before the water goes. Jacuzzi says it prevents damage to the tub's components.
- Use only the shell cleaner your maker lists, and leave no soap behind. Jacuzzi and Sundance warn it causes severe sudsing in the new fill.
- Refill through the filter if your tub airlocks. Hot Spring always fills that way; Jacuzzi and Sundance say the footwell usually works.
- A line purge is optional. If you use one, it goes in before the drain, and its label sets the dose and run time.
- Do not leave a tub empty in freezing weather. Jacuzzi and Sundance warn the lines and equipment can freeze.
Before the drain: a purge, if you use one
Your tub has several feet of pipework feeding the jets, and nothing scrubs the inside of it. The CDC says biofilm, the film bacteria build on wet surfaces, can shelter Legionella and Pseudomonas from sanitizer, and that it doesn't come off with gentle rinsing.
A line purge product is meant to lift it out while the old water is still in, so it leaves with the drain. None of the five makers' manuals I read mentions one, so treat it as optional rather than a step you've been skipping.
If you use one:
- 1
Add it to the old water
Dose by the product's label, for your tub's volume.
- 2
Run the jets for as long as the label says
Keep the filter in. Some purge labels say to take it out, but Hot Spring, Jacuzzi, Sundance and Bullfrog all say never to run the tub without its filter.
- 3
Then drain
Whatever the purge lifted out goes with the old water.
Draining
By gravity: find the drain valve, attach a garden hose and open it. That's the method every maker's manual describes. Bullfrog says its drain runs at about 5 gallons a minute, so a 400 gallon tub takes over an hour. Hot Spring says its tubs drain almost completely this way, with a secondary drain for the last gallon or so in the bleed lines.
By submersible pump: drop it in the footwell and run it. How fast depends on the pump: at 1,200 gallons an hour, 400 gallons takes about 20 minutes.
Sponge out the footwell if you want it dry for cleaning.
Where the old water goes
Four hundred gallons has to end up somewhere.
Let the sanitizer fall first. Bullfrog says that if you drain onto plants or grass, the chlorine or bromine must be below 0.5 ppm, and Hot Spring warns that water with a high sanitizer level may harm plants and grass. Stop dosing ahead of the drain, leave the cover open, and test before you open the valve.
Not where it can do damage. Bullfrog says to drain to an area that can take a large quantity of water, away from basement window wells. Hot Spring says to run a hose from the valve so the water doesn't flood the foundation around the tub.
Ask before using a drain. Whether spa water may go down a storm drain or into a sewer cleanout is a local rule. One call to your water or sewer authority settles it, once, for every drain afterward.
Cleaning the shell
Now the tub is empty and you can see what the waterline has been doing.
Use what your tub's maker lists, with a soft cloth, because the makers don't agree:
- Hot Spring: plain water, its own Spa Shine, or Soft Scrub, and nothing else. It says most household chemicals harm the shell, and names Windex and Simple Green among the products not to use.
- Bullfrog: mild dish-washing soap, window cleaner, or what your dealer recommends, with a mild acrylic cleaner or mild detergent for stubborn stains. For the waterline, a spa surface cleaner.
- Jacuzzi and Sundance: nothing abrasive and nothing that attacks the surface. If you're unsure about a cleaner, they say to ask your dealer.
So the window cleaner Bullfrog allows is one Hot Spring bans. On a tub from any other maker, a spa surface cleaner is the safe choice.
Clean or replace the filter now, while the tub is empty and you have room to work. Hot Spring says to clean and rotate the cartridges every time the tub is drained.
Refilling without an airlock
Where the hose goes depends on your tub, and the makers say different things.
Hot Spring says to refill through the filter compartment, using its Clean Screen pre-filter on the hose. Jacuzzi and Sundance say that in most cases filling through the footwell won't cause an airlock, and recommend the filter fitting if one happens. Bullfrog says to open all the valves and jets before filling, so air can escape as the water rises.
Filling through the filter works on all of them, so if your tub has ever airlocked, start there.
Hot Spring adds a temperature rule: the refill water should be between 50 and 70°F, because colder water can trip the high-limit, and it doesn't recommend refilling at all when the air is below 50°F.
- 1
Fill to the right level
Jacuzzi says to take the cartridge out if you fill through its filter fitting; Hot Spring fills with the filters in. Fill until the water covers every jet but doesn't touch the bottom of the lowest headrest, which is Jacuzzi's mark.
- 2
Fit the filter and restore power
Breaker back on, then the control panel.
- 3
Run each jet pump briefly and listen
Water moving means you are fine. A pump running with no flow means air is trapped.
- 4
If it is airlocked, purge the air
Power off. Jacuzzi's fix: take the filter cartridge out, hold the hose over the filter fitting with a rag sealed around it, and have a helper run the water for 30 seconds. Bullfrog's: take the clamp off the air bleed line at the pump and pull the line off until the air is out and water flows, then reconnect it. Hot Spring runs a ten-minute clean cycle to purge air from the heating system. If the pump still won't prime, the weak jets guide has every maker's method side by side.
Balancing the new fill
Fresh water is not balanced water, and tap water varies enormously.
Balance it to your tub maker's ranges, which differ more than you'd expect. The hot tub chemistry guide sets them out maker by maker, and the test log works out the doses for your tub.
- Total alkalinity before pH. Hot Spring's and Bullfrog's manuals both say so, and so does the Pool & Hot Tub Alliance: pH won't hold until alkalinity is right.
- Then pH.
- Calcium hardness. Bullfrog warns that soft water can stain the shell and corrode the tub's equipment. Hot Spring and Caldera want 75 to 150 ppm; Jacuzzi, Sundance and Bullfrog want 150 to 250.
- Then sanitizer, to your maker's range, dosed by the product's label. Bullfrog says to super-sanitize every new fill.
Let it heat and circulate, then test again the next day. A fresh fill moves as it warms.
For a fresh fill
- Check price
hose-end fill filter
Catches sediment and metals on the way in, which is the only easy time to catch them.
- Check price
AquaDoc bromine booster (sodium bromide)
Sodium bromide, the first half of a two-part bromine system. Jacuzzi and Sundance say not to use it with ozone or UV.
- Check price
AquaChek Select Connect test strips
Fine for a quick mid-week pH check. Not for decisions that cost money.
In freezing weather
Do not leave a tub sitting empty when it might freeze.
Draining doesn't make a tub freeze-proof. Jacuzzi and Sundance warn that in extreme cold the lines and equipment can freeze, and Hot Spring says any water left in the plumbing has to come out to winterize. A full, running tub has its controls on its side: Bullfrog's check the water and heat it when they detect freezing conditions. An empty one has nothing.
If you're shutting down for winter, follow the winterizing steps in your manual. The winter guide sets out what each maker's steps have in common, and where they differ. It's the same logic as closing a pool, on a smaller scale.
Go deeperThe freeze-protection logicWhy water left in equipment is what actually does the damage.Frequently asked questions
How do you drain a hot tub fast?
The drain valve and a garden hose, the method every maker's manual describes, is the slow way. Bullfrog says its drain runs at about 5 gallons a minute, so 400 gallons takes over an hour. A submersible pump in the footwell goes as fast as its rating: at 1,200 gallons an hour, 400 gallons takes about 20 minutes. Cut the power at the breaker first either way.
Why does my hot tub pump not work after a refill?
Usually an airlock: air trapped in the plumbing, so the pump runs without moving water. Jacuzzi's fix is to turn the power off, take the filter cartridge out, hold the garden hose over the filter fitting with a rag sealed around it, and have a helper run the water for 30 seconds. Bullfrog's is to take the clamp off the air bleed line at the pump and pull the line off until the air is out and water flows, then reconnect it. Hot Spring runs a ten-minute clean cycle to purge air from the heating system.
What should I clean the inside of a hot tub with?
What your tub's maker lists, because they disagree. Hot Spring allows only plain water, its own Spa Shine, or Soft Scrub, and names Windex and Simple Green among the products not to use. Bullfrog allows mild dish-washing soap, window cleaner or what your dealer recommends. Jacuzzi and Sundance rule out abrasives and say to ask your dealer. Whatever you use, rinse until none is left: Jacuzzi and Sundance warn that soap left on the shell causes severe sudsing when the tub is refilled.
Do I need to purge hot tub lines before draining?
It's optional. None of the five makers' manuals I read mentions a purge product. The case for one is biofilm: the CDC says Legionella and Pseudomonas bacteria can live in it, protected from sanitizer, and that it doesn't come off with gentle rinsing. If you use one, follow its label for the dose and the run time. If a label tells you to take the filter out while the jets run, check that against your manual first: Hot Spring, Jacuzzi, Sundance and Bullfrog all say never to run the tub without it.
Can you leave a hot tub empty?
Not for long in hot sun, and not in freezing weather. Jacuzzi and Sundance say not to leave the empty shell in direct sunlight when it's hot outside, and warn that in extreme cold the lines and equipment can freeze. For a real winter shutdown, follow your manual's winterizing steps.
