How to drain a hot tub: a step-by-step guide
Draining a hot tub has a reputation for being slow, but it does not have to be. The built-in drain valve can take a couple of hours to empty a full tub. A submersible pump does the same job in minutes. This guide walks you through the whole process, from the first drain to a clean refill.
Quick summary
Drain your hot tub with a submersible pump to empty it in minutes. First flush the pipes, then switch off the power. Pump out the water, clear the base, and wipe the shell. Refill through the filter housing and balance the chemicals. Do this every three to four months for clean, safe water.
Why do you need to drain a hot tub?
Even with perfect dosing and testing, hot tub water doesn't last forever. There are two main reasons you eventually need to start fresh:
Hidden hygiene issues: bacteria and grime slowly build up inside the plumbing where your sanitiser can't reach. A full drain lets you flush those lines so your new water stays clean longer.
Chemical buildup: every soak leaves behind body oils, lotions, and spent chemicals. These accumulate as total dissolved solids (TDS). Once TDS levels get too high, the water becomes impossible to balance.
Your water will usually tell you when it has reached its limit. Look out for these warning signs:
Chemical readings won't hold steady.
You're constantly adding chemicals with little to no effect.
The water looks dull or cloudy.
There's a stale, lingering odour.
A scaly film starts forming around the shell.
Cloudy, green-tinged water is a clear sign it's time to drain and refill.
How often should you drain a hot tub?
As a general rule, you should drain and refill your hot tub every three to four months. Over time, the water becomes too saturated with minerals and spent chemicals, stopping your sanitiser from working and turning the water cloudy. Fresh water balances quickly and protects your pump and heater.
However, your actual schedule depends heavily on how often you soak:
Standard use: every 3 to 4 months.
Heavy use (daily or with large groups): every 1 to 2 months, since the water saturates much faster.
If your chemicals start drifting out of range within days, it's a clear sign it's time for a change. Draining on schedule is part of good hot tub maintenance, and it saves you money on extra chemicals by keeping every soak clean and safe.
What you need before you start
Gather a few basics first. The right kit turns a draining day into a quick job:
Hot tub line flush cleaner: Clears hidden bacteria from inside the pipes.
A submersible pump: Sits on the tub floor and pumps water out in minutes, not hours.
A garden hose: Directs the drained water to a safe drain away from the house.
A wet vacuum or puddle pump: A low-level pump that clears the last few centimetres.
Hot tub cleaner: A purpose-made cleaner that protects the acrylic shell from damage.
A clean or new filter: Ready to fit before you refill, for clear water from the start.
Lay everything out before you begin. This way you drain, clean, and refill in one smooth run.
A submersible pump is what makes the fast method possible.
How to drain a hot tub
Start by flushing the pipes. Add a line flush cleaner, run the jets for around twenty minutes, then switch them off. This clears hidden bacteria, called biofilm, from inside the pipework. Next, switch the hot tub off at the mains to protect the pump and heater from running dry. If the water is still warm, let it cool first, then choose your method below.
Method 1: With a submersible pump (the fast way)
A submersible pump sits on the floor of your tub and empties it in ten to twenty minutes.
Place the pump at the deepest point of the tub, usually the footwell.
Connect the drainage hose and run it to a suitable drain.
Plug the pump into an RCD-protected socket, keeping the cable clear of the water.
Switch the pump on and let it empty the tub.
Turn it off as soon as the water is gone, so it never runs dry.
Clear the last few centimetres with a wet vacuum or puddle pump.
Our pick of submersible pumps for draining your hot tub
Method 2: With a garden hose (no pump)
No pump to hand? The built-in drain valve works by gravity. It is far slower, usually one to two hours, but it needs no extra kit.
Find the drain valve, usually behind a panel near the base of the cabinet.
Screw on a garden hose, but do not overtighten it, as the plastic threads crack easily.
Run the hose to a suitable drain and open the valve.
Once empty, clear the last few centimetres with a wet vacuum.
Note: A submersible pump does the same job in a fraction of the time, so it is worth having one if you drain your tub regularly.
Clean your hot tub before refilling
While the tub is empty, give it a wipe. Clean the shell, jets, and headrests with a hot tub cleaner. Avoid household products, as these can damage the acrylic. Rinse your filter or fit a clean one, ready for the refill.
Wipe down the shell, jets, and headrests while the tub is empty. Image: Shutterstock.
Where to safely dispose of hot tub water
Never drain chlorinated water straight onto your lawn or into a stream, as active chlorine and bromine will severely harm plants, soil, and wildlife. Fortunately, the safe route is simple: just stop adding sanitiser one to two days before you plan to drain. Once your test strip reads near zero, the neutralised water is perfectly safe for your garden or a surface drain.
If you need to empty the tub immediately, you must direct the treated water into a foul sewer instead. The same rules apply when you are draining a swimming pool. Always attach a garden hose to the pump outlet so you can easily direct the flow and keep the water well away from your home's foundations.
How to refill and balance your water
Refilling is simple, and it needs no special equipment beyond a hose. Place the hose in the filter housing and fill from there, rather than over the top. This fills the pipework first and prevents an airlock, the trapped air that blocks the flow and can trigger a flow error on your control panel. Fill until the water sits just above the top jets, then switch the power back on.
Now balance the water. Adjust total alkalinity first, then pH, then your sanitiser, in that order. Give the tub a few hours to warm up before the first soak. Keeping it balanced week to week soon becomes routine.
Enjoy your hot tub again
Draining your hot tub does not need to be a chore. Flush the lines, switch off the power, and let a submersible pump do the heavy work. Wipe the shell, dispose of the old water safely, then refill and balance. The right pump turns a long job into a quick one.
Not sure which pump suits your hot tub? Our customer service team is happy to help you find the right one for your setup.