How to Drain Your Hot Tub Using the Drain Valve

Changing the water in your hot tub is one of the few maintenance tasks you really do need to do — typically every 4–6 months for a home spa (new owners often do the first change at 2–3 months), more often for heavily used or commercial spas. Fortunately, the drain valve at the bottom of your spa is designed to make it straightforward. This guide walks you through the procedure, plus a few UK-specific notes on where to drain the water to and how to refill cleanly.

Once you know the valve works, the next question is timing: our guide to how often to drain and refill a hot tub sets a practical UK schedule and the signs that mean change the water now.

Watch the video walkthrough

How the drain valve works

The drain valve at the bottom of your spa has a simple but well-designed locking mechanism. When the valve is extended outwards, the water is held back so you can attach (or remove) a garden hose without anything spilling. When the valve is pushed back in and twisted, the water flows. That two-stage operation is what makes it safe to thread a hose on without flooding the cabinet base while you do it.

The one mistake to avoid: only unscrew the cap

The most common drain-valve problem we see is owners unscrewing the whole drain unit instead of just the cap in its centre. The unit is screwed into the spa’s plumbing, so turning the whole thing detaches it and water leaks inside the cabinet rather than down the hose. If this happens, stop, remove the cabinet panel next to the drain valve and screw the unit back in until it is secure. The video above shows the correct movement.

Always check the valve is pulled out (not pushed in) before you remove the cap. In the “out” position the valve holds the water back, so nothing escapes even if the cap goes back on cross-threaded.

Before you start: a few important notes

• Power off: always shut off the spa at the breaker (or unplug a 13-amp plug & play model) before draining. Running the heater or pumps dry will damage them.
• Cool the water down: hot water shouldn’t be drained straight onto a lawn or borders. Either cool the spa to ambient temperature for a few hours before draining, or direct the discharge somewhere it can’t damage planting.
• Choose a sensible discharge point: see the UK drainage section below.
• Have a clean hose ready: a standard UK garden hose with a male threaded end is what fits the drain-valve cap.

Step by step: emptying the spa

1. Check the drain valve is extended outwards, then unscrew only the cap from the middle of the valve — not the whole unit.
2. Screw the male threaded end of your garden hose into the now-exposed valve, and run the other end of the hose to wherever you’ve planned to send the water.
3. When you’re ready, push the valve back in and twist it to release the water.

Gravity does the work from here. A typical home hot tub holds 800–1,400 litres and takes a few hours to fully drain. There’s no need to stand and watch it; check back periodically, and close the valve once the spa is empty.

Clearing the last of the water

A small amount of water always stays in the footwell, pipework and jets. Use a wet/dry vacuum to suck out what is left in the footwell and from each jet head. If your spa has an air blower, you can briefly restore power and run the blower for about 10 seconds to push trapped water out of the air lines, then switch the power off again. Only run the blower this way — never the pumps or heater, which must not run without water.

Where to drain the water in a UK garden

This is the bit that catches new owners out. UK gardens often slope, soils don’t always drain quickly, and you don’t want a few hundred litres of treated spa water destroying a freshly seeded lawn or a rose bed. Sensible options:

• The household foul drain — usually the safest discharge point. Most UK properties have a foul-water drain in the back garden you can hose into.
• A surface-water drain or soakaway if your area has one and your local authority allows it.
• A stretch of paving or paved patio that slopes away from the house and any planting — useful if the water is well-cooled and chlorine/bromine has dissipated (give the spa 24–48 hours after stopping sanitiser dosing before draining if you’re going this route).
• Avoid: draining onto lawns, borders, vegetable beds, ponds, or anywhere the water will pool. Spa chemistry is fine in a swimming pool quantity but harsh on garden plants in concentration.

Check your local water company’s guidance if you’re unsure — most accept hot tub water into the foul drain.

While the spa is empty

This is the ideal opportunity to do a few maintenance jobs that are awkward when the spa is full:

• Wipe down the shell with a non-abrasive spa-safe cleaner. Avoid household scrubbers — they can scratch the acrylic.
• Clean the filter housing and rinse or replace your filter cartridges. A clean filter is the single biggest difference-maker for water clarity on the next fill — see our guide on how often to clean your hot tub filter.
• Check the cover seals and underside for any moisture damage. If your cover is sagging or no longer sealing properly, it’s worth considering a replacement cover before you refill.
• Wipe out the footwell and around the drain valve while everything is dry and accessible.

Refilling cleanly

When the drain is complete, twist the valve and pull it back out to close it, unscrew the hose, and replace the cap. To refill:

1. Remove the filter cartridges from the housing temporarily.
2. Place the garden hose inside the filter housing rather than into the open shell — this helps prime the pumps and minimises trapped air.
3. Refill until the water reaches the recommended fill line on the spa.
4. Refit the clean filter cartridges.
5. Restore power and let the spa run a full priming cycle. Check for any leaks at the drain valve and unions before letting the spa heat up.
6. Balance the water chemistry from scratch — alkalinity, pH, then sanitiser. Don’t get in until everything is in range.

Frequently asked questions

How often should I drain and refill my spa?

Every 4–6 months is normal for a home hot tub, depending on use, and new owners often do the first change at 2–3 months. More often for heavily used spas, holiday lets, or any spa where the water is starting to look or smell off despite balanced chemistry.

How long does it take to drain a typical hot tub?

2–4 hours for most home spas via the gravity-fed drain valve. Larger spas or longer hose runs can take longer. A submersible pump can speed things up if you have one, but the drain valve is enough for most owners.

Can I drain a spa straight onto the lawn?

It’s not recommended unless the water is cool and the chemistry has fully neutralised. Spa water in concentration can damage lawns and plants. The foul drain or a sloping paved area is safer.

What if my drain valve won’t extend or twist?

The valve can stiffen with limescale or grit if the spa hasn’t been drained in a while. A bit of gentle persuasion usually frees it. If it’s seized completely, contact our support team or arrange a service visit — don’t force it.

I unscrewed the whole drain valve and now it’s leaking inside the cabinet. What do I do?

Close the valve if you can, switch the spa off at the breaker, and remove the cabinet panel next to the drain valve. Screw the drain unit back into its fitting until it is secure, then check for drips before refilling. If the fitting is damaged or still leaks, see our guide to locating a leak or contact our support team.

Do I need to drain the spa to clean the filters?

No. Filter cleaning is a separate, more frequent task — every 2–3 weeks for a routine rinse, monthly for a chemical soak. Full drain and refill is the every-4–6-months reset.

Should I drain my hot tub for the winter?

Not usually. A tub kept running and covered through the winter is protected from freezing by its own circulation and heater. If you plan to leave it off for a long period, read our guide on whether to empty your hot tub in winter first, because water left in the pipework can freeze and crack fittings.

Are there signs I should drain early?

Yes. Drain before the usual 4 to 6 months if the water stays cloudy or foamy after you have cleaned the filter and shocked it, if it smells stale despite balanced readings, or if the chemicals stop holding their levels. The pH drifting up and down is another sign, often caused by too much detergent in the water, and a full change is a good idea.

How much water will I need to refill?

It depends on the model: about 350 litres for a Yukon, 700 litres for a Calgary or Montreal, and 1,465 litres for a Niagara. Fill to about 25 mm above the waterline.

A simple job, done properly

The drain valve is one of the most well-engineered parts of your spa — designed to make a routine job painless. Get the discharge point right, take the chance to clean while the spa is empty, and you’ll be back to balanced water within a few hours of refilling. If your spa has been a while between services, a full drain is also a good opportunity to book a service visit so an engineer can check the components you can’t see.

Keep your water clear

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