Bidet attachment running costs: how much water do you use in the UK?

If you’re fitting a bidet attachment to a standard UK toilet and using it sensibly, the water running cost is usually modest. The biggest day-to-day change is often that you use far less toilet roll (and ideally avoid wet wipes), rather than dramatically changing your total water bill.

To estimate your own cost, you need two numbers: roughly how much water the bidet uses per wash, and how much that adds to your annual water use. Below are practical UK ways to work it out, plus what payback usually looks like in real homes.

How much water does a bidet attachment use?

A bidet attachment is cold-water only, fed from the toilet’s existing supply via a small connector at the cistern. Because it’s cold water and the spray time is short, the total water used per wash is typically a small fraction of what a toilet uses each flush.

In plain terms:

• Toilet flushes dominate your toilet water use. They can be several litres per flush depending on the toilet and settings.
• Bidet use is usually measured in seconds. The water added over the day depends on how long you run the spray and how often you use it.

If you want a quick estimate without getting lost in plumbing maths, do a simple “trial week”:

• Pick a normal number of uses (for example, morning and after the toilet).
• Time how long you let the water run each use.
• Measure the total use across 7 days (even a rough check helps you set a sensible spray duration).

Once you know your pattern, you can translate that into cost using your water bill rates (see the next section).

Working out running costs from your water bill (UK method)

UK water bills often include both water (supplied by your water company) and wastewater (what you send to the sewer). Many bills show either separate charges or a combined per-metre-squared rate, plus standing charges.

To keep it simple, focus on the variable part: the charge per cubic metre (m³). 1 m³ equals 1,000 litres.

Your calculation steps:

• Find your cost per m³ on your bill (water plus sewer, if your bill separates them).
• Estimate litres used by the bidet per wash. If you know your spray time, you can refine this, but you can also use a practical range and adjust after a week.
• Multiply by your weekly and annual use (weekly uses times litres per use, then multiply by 52).
• Convert litres to m³ by dividing by 1,000.
• Multiply by your £ per m³ to get your annual running cost.

The standing charge won’t change with a bidet, so you’re mainly calculating the extra variable water amount.

Toilet roll, wet wipes and the real savings

When people ask about bidet “savings”, they’re usually comparing the cost of toilet roll and wet wipes against the cost of added water. That’s often the right comparison.

• Toilet roll spend: A bidet attachment can reduce the amount of dry wiping you need for day-to-day use. How much you save depends on how you use it and how absorbent your preferred paper is.
• Wet wipes: Many people replace flushable wipes with a bidet, but it’s important to remember that “flushable” doesn’t always mean it’s trouble-free for plumbing systems. Using a bidet and sticking to fewer wipes (or none) can reduce this ongoing spend.

To estimate your savings, look at your last couple of months of household spend on toilet roll and wipes, then set a sensible goal such as:

• Reduce toilet roll usage by a set percentage (for example, start with 25 to 50% and adjust after a month).
• Reduce or stop wet wipes depending on what you currently use.

If your current spend on paper products is significant, even modest water usage from a bidet can be more than offset.

What running costs include, and where payback comes from

A realistic payback period comes from the gap between:

• Extra water cost from bidet use
• Reduced household costs from less toilet roll and fewer wipes

On the cost side, think beyond water:

• Installation: A non-electric attachment typically connects to the toilet’s cold supply and installs quickly with the right UK-spec plumbing parts. That can reduce the need for labour costs compared with some “bigger” bathroom changes.
• Maintenance: Cold-water attachments are usually simple to keep working. You may occasionally check for leaks and ensure filters or connectors are clean if your supply requires it.

On the savings side, you can usually get a feel for payback fairly quickly:

• Calculate your monthly paper spend change (toilet roll and wipes).
• Subtract your estimated monthly water increase.
• Divide the purchase cost by the net monthly saving.

In many UK households, the payback will be driven mainly by reduced toilet roll and wipes, not by water alone, because toilet roll and wipes tend to cost more than the extra litres of water used per day.

UK plumbing and usage habits that affect consumption

Bidet use is affected by how your system delivers water and how long you run it. A few UK-specific practical points help keep costs under control:

• Cold-water only: Since the water is fed from the toilet cistern supply, your water stays at mains temperature, and you’re not adding energy costs for heating.
• Timing matters: Short, consistent use usually costs less than long “rinses”. Set a comfortable spray duration and stick to it.
• Stop leaks quickly: Any dripping or leakage around the connection will add water waste over time. Check after installation and after a few weeks.

If you’re choosing equipment for UK plumbing, it’s worth confirming it’s built for standard UK connections. Real Bidets sells a non-electric, cold-water bidet toilet seat attachment that uses UK-spec parts, including a 15mm copper pipe compression fitting and a 1/2 inch T-junction, which helps avoid the adapter hassle that can come with US-spec kits.

Frequently asked questions

Will a bidet attachment noticeably increase my water bill in the UK?

Usually it won’t be a big jump if you keep the spray time sensible. Toilet flushing still uses far more water than short bidet sprays for most households.

How many times a day should I use it to keep costs down?

Use it as often as you need for hygiene, but keep each use brief. Many people find that once they’re set up and comfortable, the time per use naturally stays consistent.

What’s the fastest way to estimate payback for a bidet attachment?

Work out your monthly savings on toilet roll and wipes first, then subtract your estimated added water cost from that. With a trial week and your next bill, you can tighten your estimate.

If you want to cut toilet roll and wipe costs without major plumbing work, a non-electric cold-water bidet attachment from Real Bidets is a practical starting point. If you’d rather try bidet-style rinsing with more flexibility, a handheld sprayer (shattaf) is another sensible option to consider.

Related guides

• How to install your Real Bidet (UK guide)
• 15mm copper pipe? Here is the fix
• Bidet attachments vs bidet toilet seats

UK-spec as standard: Real Bidets kits include a 15mm copper pipe compression fitting and a 1/2 inch T-junction, so they connect straight to UK plumbing without extra adapters.