If you’ve just bought a hot tub, or you’re thinking about it, one of the first questions that pops up is this:
“How much water does it actually use?”
It’s a fair question. Between rising water bills and general upkeep, you want to know what you’re signing up for. The good news? It’s a lot less dramatic than most people think, but there are a few details that catch people out.
Let’s break it down properly.
The Short Answer (If You’re in a Hurry)
Most hot tubs in the UK use:
- 800 to 1,500 litres of water per fill
That’s for your typical 2–6 person hot tub, which covers most inflatable tubs and a good chunk of hard-shell models.
But the real question isn’t just how much it holds, it’s how often you’re replacing that water. That’s where the actual usage adds up.
Typical Hot Tub Sizes (UK Examples)
Here’s a rough guide based on what most people have in their gardens:
- Small (2–3 people): 700–900 litres
- Medium (4 people): 900–1,200 litres
- Large (5–7 people): 1,200–1,800 litres
If you’ve got something like a Lay-Z-Spa (which a lot of UK homes do), you’re usually sitting around the 800–1,000 litre mark.
Hard-shell tubs tend to creep higher, especially if they’ve got deeper seating and more jets.
How Often Do You Change the Water?
This is where most people either overdo it… or leave it far too long.
As a general rule:
- Every 3 months for regular use
- Every 1–2 months if it’s getting heavy use (kids, parties, daily dips)
- Longer (maybe 3–4 months) if you’re meticulous with chemicals and filtration
So, if your tub holds 1,000 litres and you change it every 3 months:
You’re using around 4,000 litres per year
That’s your real annual water usage.
What Does That Mean for Your Water Bill?
Let’s keep it simple.
In the UK, water costs vary, but a rough average is:
- £2 to £4 per 1,000 litres
So:
- One full refill = £2 to £6
- Yearly water usage = £8 to £25
Honestly? The water cost is one of the cheaper parts of owning a hot tub.
Electricity and chemicals will hit your wallet far more. You can learn more about them costs in our How Much Does It Cost to Run a Hot Tub in the UK?
How Long Does It Take to Fill a Hot Tub?
This depends on your hose pressure, but in most UK homes:
- 1,000 litres = 1.5 to 3 hours
If your pressure’s decent, you’ll be closer to the lower end. Older plumbing or long hose runs? Expect it to take a bit longer.
Pro tip from experience:
Start filling it earlier than you think, no one enjoys staring at a half-full tub on a Friday evening. Just remember to also factor in the heat up time.
What Affects Water Usage?
Not all hot tub owners use the same amount of water. A few things make a big difference:
1. How Many People Use It
More people = more contaminants (oils, sweat, lotions).
That means your water gets dirty quicker… and needs changing sooner.
2. How Often You Use It
Weekend use? Your water lasts longer.
Daily use? You’ll be draining and refilling more often.
3. How Well You Maintain It
This is the big one.
If you:
- Keep your chemicals balanced
- Clean your filters regularly
- Shower before getting in (yes, it matters)
You’ll stretch your water life much further.
If you don’t… you’ll know about it. Cloudy water, odd smells, and a drain-and-refill job sooner than expected.
4. Debris and Environment
Trees, grass, bugs, they all end up in your tub if it’s not covered properly.
A good cover doesn’t just keep heat in, it keeps your water cleaner for longer.
Inflatable vs Hard-Shell: Is There a Difference?
Yes, but not massive.
- Inflatable tubs (like Lay-Z-Spa):
Tend to use less water (800–1,000 litres) - Hard-shell tubs:
Usually larger, deeper, and hold more (1,200–1,800+ litres)
But the bigger difference is often usage habits, not the tub itself.
People with permanent hard-shell tubs tend to use them more, which means more frequent water changes.
A Simple Way to Estimate Your Own Usage
If you want a quick, no-nonsense calculation:
- Check your tub’s capacity (in litres)
- Multiply it by how many times you’ll change the water per year
Example:
- 1,000 litre tub
- Changed every 3 months (4 times a year)
👉 1,000 x 4 = 4,000 litres per year
That’s your answer.
The Bottom Line
Hot tubs don’t use as much water as people assume.
For most UK owners:
- Per fill: 800–1,500 litres
- Per year: Around 3,000–6,000 litres
That’s roughly the same as a few long baths a week, not excessive, especially when you look at the enjoyment you get out of it.
If you stay on top of maintenance, you’ll keep that number on the lower end. Ignore it, and you’ll be draining it more often than you’d like.
Final Words
If there’s one thing I’ve learned over the years, it’s this:
Hot tubs don’t become expensive because of water, they become expensive when people don’t maintain them properly.
Look after your water, and it’ll look after you.
And if you’re ever unsure… clear water, no smell, and balanced chemicals, that’s what you’re aiming for.
