Toilet Flush Water Usage Calculator
Toilet flushing is one of the biggest hidden contributors to a household's water bill, and small changes in flush volume or habits add up quickly across a family. Enter your flush type and household size below to see your estimated usage and cost.
Estimate your household's toilet water usage
Choose your flush type and enter your household's flushing habits.
Estimated usage: 90 litres/day
630 litres per week
That's roughly £1.26 a week in water and sewerage costs, based on a typical UK combined rate.
Recommended products
A few well-reviewed toilet accessories to consider.
- Stainless Steel
- Silver
£13.99
Pros
- 304 stainless steel resists rust in damp bathrooms
- 2-piece set includes matching towel ring
- Simple wall-mounted fitting
Cons
- Wall fixings required — no self-adhesive option
- Chrome-Plated Steel
- Chrome
£13.99
Pros
- Free-standing — no drilling or wall fixing needed
- Holds a spare roll plus 3 more in the base caddy
- 5-year rust-free guarantee
Cons
- Takes up floor space next to the toilet
- Ceramic
- White
£16.50
Pros
- Ceramic base wipes clean easily
- Metal handle brush feels sturdier than plastic sets
- Compact footprint suits most bathrooms
Cons
- White ceramic can show limescale marks over time
Frequently asked questions
How much water does an older toilet use compared to a modern one?
An older single-flush toilet can use around 9 litres per flush, compared to 4-6 litres for a modern dual-flush model, so switching can noticeably cut a household's water use over a year.
What is the difference between the full and reduced flush on a dual-flush toilet?
The full flush (usually around 6 litres) is designed for solid waste, while the reduced flush (around 4 litres) is meant for liquid waste, and using the reduced option whenever possible is one of the easiest ways to save water day to day.
Is toilet flushing really a big part of household water use?
Yes — flushing typically accounts for a significant share of indoor water use in a UK home, often rivalling or exceeding showers, simply because it happens so many times a day across everyone in the household.
Can I reduce my flush volume without replacing the toilet?
Fitting a cistern displacement device or adjustable dual-flush valve can reduce the volume used per flush on an existing toilet, giving some of the water savings of a new unit without the cost of full replacement.
How this calculator works
The calculator uses an average flush volume based on the type of toilet you select. Older, older-style toilets can use up to 6 litres per flush, whereas newer, dual-flush models typically use between 3 and 8 litres. The calculator multiplies this average flush volume by the number of flushes your household makes each week – we’ve factored in an average of approximately 4 flushes per person per week for a typical family.
The results are presented as a weekly water usage figure, measured in litres. This allows you to compare your toilet's consumption with other appliances in your home and identify areas where you could potentially reduce water waste.
Toilet Flush Types & Average Flush Volumes (UK)
- **Older Style Close Coupled Toilet:** Approximately 6 litres per flush. These are increasingly rare in new builds but still common in older properties.
- **Older Style Overhead Flush Toilet:** Typically uses around 8-10 litres per flush – often found in older terraced houses.
- **Dual Flush Toilet (Low Flow):** A good balance, usually using between 3 and 6 litres for a liquid flush and 4-7 litres for a solid flush. Many newer models offer adjustable flow rates.
- **Wall Mounted Dual Flush Toilet:** Generally uses 4-7 litres per flush, offering improved aesthetics alongside water efficiency. Consider options from brands like Villeroy & Boch or Duravit.
- **Back to Wall Toilet (Low Flow):** Similar usage to wall mounted models – expect around 5-8 litres for a liquid flush and 6-9 litres for a solid flush.
- **Composting Toilet:** These use significantly less water, typically under 1 litre per ‘flush’ relying on natural decomposition. Consider brands like Separett.
- **High-Efficiency Dual Flush (Advanced):** Some modern designs can achieve as little as 2.5 litres for liquid and 3 litres for solid – look for WaterSense certified models.
- **Toilet with Pressure Assist:** These use a small amount of water, roughly 4-6 litres per flush, and rely on air pressure to improve flushing power.
- **Greywater Recycling Toilet (Specialist):** These innovative toilets recycle water from showers or sinks – usage varies greatly depending on the system's design but often around 3-5 litres per flush.
Worked example: A Typical Family
Let’s say you have a family of four (two adults, two children) using a standard dual-flush toilet. We'll assume an average usage of 5 litres per liquid flush and 6 litres per solid flush – totalling 11 litres per flush. The calculator estimates they would use approximately 264 litres of water per week (4 people x 64 flushes per week, with an average flush volume of 11 litres).
This figure represents a significant amount of water. By upgrading to a dual-flush toilet that uses only 6 litres per flush and reducing the number of unnecessary flushes, you could potentially reduce weekly usage by around 200 litres – saving approximately £48 on your water bill over a year (based on a typical UK water tariff). You can find suitable dual-flush options from brands like TOTO, Geberit or Ideal Standard on Amazon UK.
More questions answered
How does the calculator account for different flushes?
The calculator uses pre-defined average flush volumes based on toilet type. You can adjust the number of liquid and solid flushes to reflect your household’s specific behaviour, but keep in mind that this will impact the final result. It's best to be as accurate as possible with the numbers you enter.
What if I have a very small bathroom?
A smaller bathroom may lead to fewer flushes overall. Consider reducing the number of flushes you input into the calculator, but don’t underestimate your water consumption – even short flushes add up over time.
Does this calculator include toilet seat cleaning?
No, this calculator focuses solely on the water used during flushing. Toilet seat cleaning typically uses a much smaller amount of water and isn't factored into the calculation.
Can I use this to compare different types of toilets?
Yes! The calculator allows you to input the type of toilet you have (e.g., dual-flush, close coupled) and see how its estimated usage compares to other options. This helps in making informed purchasing decisions.
What if I only flush once a day?
Reduce the ‘flushes per person per week’ value to reflect your reduced flushing frequency. A single daily flush would significantly lower the calculated water usage.
How accurate is this calculator?
This calculator provides an estimate based on average figures. Actual water usage can vary depending on individual habits, toilet maintenance, and the specific model used. It's a useful starting point for understanding your consumption.
What if I have a very old toilet?
Older toilets are notoriously inefficient. Inputting the maximum estimated flush volume (around 6 litres) will give you a more realistic assessment of water usage, highlighting the potential savings from upgrading.
I've upgraded to a low-flow toilet – how does this calculator reflect that?
Adjust the ‘average flush volume’ setting in the calculator to match the specifications of your new low-flow toilet. Consult the manufacturer’s details for precise figures.
Should I consider installing a water meter?
A water meter provides accurate real-time monitoring of your water consumption, which is far more reliable than estimates. Consider installing one to gain complete visibility into your household's water usage and identify potential leaks or wastage.
Are there any rebates available for upgrading to water-efficient toilets?
Check with your local water company and the government’s EcoSmart scheme for potential rebates or grants available for purchasing water-efficient appliances. These can significantly reduce the initial cost of an upgrade.