Dŵr Cymru Welsh Water charges and what a leak costs
Dŵr Cymru Welsh Water bills sewerage on 95 per cent of your metered volume, with a 5 per cent non-return-to-sewer allowance taken off the volume. Its rates per cubic metre have not been verified on this site yet, so no figure is shown here rather than a guessed one.
Last reviewed 14 August 2026. Rates correct as of 1 April 2026
The short answer
Two of the charges on a Dŵr Cymru Welsh Water bill respond to volume and one does not, and only the ones that respond to volume are part of the cost of a leak.
| Charge | Status on this site |
|---|---|
| Water, per cubic metre | Not verified yet. A notice is shown rather than a figure. |
| Sewerage, per cubic metre | Not verified yet. |
| Standing charge | Fixed. It does not change when you leak, so it is not part of the cost of one. |
How this works in practice
The cost of a leak here is the leaked volume in cubic metres multiplied by the volumetric rate, and then the sewerage rate on top only if the water reached the sewer.
- An underground supply pipe leak soaks into the ground, so no sewerage charge belongs on it.
- An internal leak that runs to a drain does reach the sewer, so both rates apply.
- A reduced share of the metered volume is billed for sewerage, because the non-return-to-sewer allowance is taken off the volume rather than built into the rate.
The mechanism matters as much as the percentage does, because applying a volume factor to a company that has already priced its allowance into the rate counts the same allowance twice. how the sewerage half of the bill is calculated works through both mechanisms and which companies use which.
What changes the answer
The rate is only one of the things that decides what a leak here costs.
- Where the water went. An underground supply pipe loss carries no sewerage charge at all, which is a larger effect than any allowance percentage.
- Whether a leak allowance is granted. It comes off the volumetric charge afterwards, so it changes the bill rather than the loss.
- The charging year. Rates and standing charges are reset annually, so a bill can rise because of a price change and a leak at the same time.
None of this changes the volume of water lost, which is the same figure in every supply area in the country. It changes only what that volume costs.
Assumptions and sources
Drip Calculator: how much water does a leaking faucet waste?
United States Geological Survey, Water Science School · primary source
- Faucet drip volume, adopted: 0.25 ml
- Faucet drip volume, measured range: 0.2 to 0.33 ml
- Bath tap drip volume: 0.5 ml
- Drips per US gallon: 15140 drips
- Drips per litre: 4000 drips
The pharmacopoeial metric drop, 20 drops to 1 millilitre
United States Pharmacopeia, British Pharmacopoeia and European Pharmacopoeia convention · primary-standard source
- Standard drop volume: 0.05 ml
Tate's law: the weight of a falling drop
Thomas Tate, Philosophical Magazine, 1864, with the later drop-weight literature · primary source
- Drop weight: W = 2 * pi * r * gamma equation
Plumbers shine the spotlight on dripping taps during Water Saving Week
WaterSafe, with Waterwise · untraceable source
- Claimed annual waste from a dripping tap: 5500 litres per year
International Organization of Legal Metrology · primary-standard source
- MPE, accuracy class 2, lower zone Q1 to Q2: 5 %
- MPE, accuracy class 2, upper zone Q2 to Q4: 2 %
- MPE, accuracy class 1, lower zone: 3 %
- MPE, accuracy class 1, upper zone: 1 %
- In-service MPE multiplier: 2 ratio
- Q2 / Q1: 1.6 ratio
- Q4 / Q3: 1.25 ratio
Aquadis+ DN15 and DN20 specification sheet
Itron · manufacturer source
- Q1 minimum flow rate, DN15, Q3 2.5, R160: 15.6 l/h
- Q2 transitional flow rate, DN15, Q3 2.5, R160: 25 l/h
- Q3 permanent flow rate, DN15: 2500 l/h
- Typical starting flow rate, DN15: 0.4 l/h
- Typical starting flow rate, DN20: 2 l/h
- Q1 minimum flow rate, DN20, Q3 4.0, R160: 25 l/h
- Flow rate at which accuracy is within +/- 5%, DN15: 3 l/h
- Flow rate at which accuracy is within +/- 2%, DN15: 5 l/h
- Minimum scale interval, DN15 and DN20: 0.02 l
Water resources 2024 to 2025: analysis of the water industry's annual water resources performance
Environment Agency · primary source
- Household per capita consumption: 136.5 l/person/day
- Household per capita consumption, prior year: 137 l/person/day
- Household per capita consumption, dry-year adjusted: 140.3 l/person/day
- National leakage: 2617 Ml/day
- National leakage as share of water put into supply: 19 %
PR24 common performance commitments: per capita consumption (PCC), version 2.1
Ofwat · primary-standard source
- PCC formula: (measured household consumption + unmeasured household consumption) / total household population l/person/day
Leaky loos, why it's not as simple as faulty flush valves
ech2o, reporting research attributed to Thames Water · secondary source
- Toilets inspected: 58551 toilets
- Toilets found leaking: 4854 toilets
- Prevalence: 8.3 %
- Average residential leak rate: 400 l/day
- Average commercial leak rate: 2100 l/day
- UK-wide average across all WCs, leaking and sound: 20 l/day
- Share of leaking toilets with flush valves rather than siphons: 81 %
Waterwise · untraceable source
- Single leaking toilet: 215 to 400 l/day
- Share of toilets leaking: 5 to 8 %
- UK total from leaking toilets: 400000000 l/day
Methods for Calculation of Evaporation from Swimming Pools and Other Water Surfaces
M. M. Shah, ASHRAE Transactions SE-14-001 · primary source
- Outdoor unoccupied pool evaporation: E0 = (C1 + C2 * u) * (pw - pa) / ifg kg/(m2*h)
- C1, SI: 235 constant
- C2, SI: 206 constant
Location-specific long-term averages, Wisley, Surrey
Met Office · primary source
- Annual mean daily maximum temperature: 15.41 degrees C
- Annual mean daily minimum temperature: 6.66 degrees C
- Annual rainfall: 667.92 mm
- Annual mean wind speed at 10 m: 5.06 knots
Discover Water, the water industry transparency site run with Water UK, Ofwat, CCW, the Drinking Water Inspectorate and Defra · primary source
- Average annual household bill, combined water and sewerage: 639 GBP
- Average annual household bill, water only: 309 GBP
- Average annual household bill, sewerage only: 330 GBP
SI Brochure: The International System of Units (SI), 9th edition (2019), version 4.01, June 2026
Bureau International des Poids et Mesures · primary-standard source
- cubic metre: coherent derived unit of the SI, Table 5 m3
- litre: non-SI unit, Table 8. 1 l = 1 L = 1 dm3 = 10^-3 m3 l or L
- bar: non-SI unit, Table 8. 1 bar = 0.1 MPa = 10^5 Pa bar
Authority URLs for the named entities in content/entities.ts
Various, see per-entity notes · primary source
WC flush volume: three UK instruments, not one
UK Statutory Instruments, Northern Ireland Statutory Rules, and Scottish Water · primary-standard source
- Maximum single flush, all three jurisdictions: 6 litres
- Dual flush, lesser flush maximum: two-thirds of the largest flush volume ratio
- England and Wales transitional maximum, 1 Jul 1999 to 1 Jan 2001: 7.5 litres
Per-event central heating top-up volume, derived
Derived by Q3 from Boyle's law and typical UK domestic expansion vessel specifications · derived source
- Water held in an expansion vessel: V_water = V * (1 - P0 / P), pressures absolute equation
- Typical top-up, 8 l vessel at 1.0 bar pre-charge, 0.5 to 1.5 bar: 1.6 litres
- Typical top-up, 8 l vessel at 0.75 bar pre-charge, 0.5 to 1.5 bar: 2.4 litres
- Typical top-up, 12 l vessel at 1.0 bar pre-charge, 0.8 to 1.5 bar: 2.4 litres
- Typical top-up, 8 l vessel at 1.0 bar pre-charge, 1.2 to 1.5 bar: 0.9 litres
- Realistic range: 0.9 to 2.5 litres
Monodispersed Bubble Generation Using Hydrophobic Orifices: The Extended Tate’s Law
Bo Liu, Hao Zhang and co-authors, ACS Omega 2024, 9(17), 18854 to 18861 · primary source
No rate on this page has been verified yet. The record exists, the source it will be read from is recorded, and until somebody has read it the page shows a notice rather than a number. A wrong rate is worse than a missing one.
The licensed appointee for this supply area is recorded as Dŵr Cymru Cyfyngedig. That is who holds the appointment, which is not always the name on the rate card, and it does not determine what you pay.
What to do next
Three things, and the first is on your own bill.
- Find the volumetric rate per cubic metre, separately from the standing charge. It is the only figure the water half of a leak cost depends on.
- Decide whether the sewerage rate applies, by establishing whether the leak is inside the building or on the supply pipe.
- Send us the rate if you have a current bill in front of you. This record exists and is waiting for a figure read from a real source rather than a guessed one.
Common questions
- Why does this page not show a Dŵr Cymru Welsh Water rate?
- Because no rate on this site has been verified yet. Every one of the 22 supply area records shows a notice instead of a figure, and will keep doing so until the rate has been read from the company's own charges scheme. A wrong rate is worse than a missing one.
- Does the standing charge go up if I have a leak?
- No. A standing charge is a fixed annual amount and does not vary with the volume you use, so a leak does not change it. Only the volumetric charge responds to volume.
- Is the licensed company the same as the one on my bill?
- The appointment for this supply area is held by Dŵr Cymru Cyfyngedig. That can be a different name from the one on the rate card, because four supply areas publish their own charges while sitting inside a larger licensed group. The rate you pay is set by the charges scheme for the area.