Water only companies, and who bills your sewerage
In 9 of the 20 England and Wales supply areas, water comes from one company and sewerage from a different one. That means two rates per cubic metre from two organisations, and the cost of a leak needs both of them.
Last reviewed 14 August 2026. Rates correct as of 14 August 2026
The short answer
A water-only company supplies your water and does not deal with your wastewater. Somebody else does that, and they set their own rate for it.
| Water supplied by | Sewerage billed by |
|---|---|
| Affinity Water | Thames Water, Anglian Water or Southern Water, depending on the area |
| Bournemouth Water | Wessex Water |
| Bristol Water | Wessex Water |
| Cambridge Water | Anglian Water |
| Essex and Suffolk Water | Anglian Water |
| Portsmouth Water | Southern Water |
| SES Water | Thames Water or Southern Water, depending on the area |
| South East Water | Southern Water or Thames Water, depending on the area |
| South Staffs Water | Severn Trent Water |
Where more than one sewerage company is named, the pairing is geographic and your own bill is the authority. Nothing on this site can tell you which side of a boundary you are on.
How this works in practice
For the cost of a leak, the split has one consequence and it is a useful one: the two halves of the bill can be affected differently by the same leak.
- A leak on the underground supply pipe never reaches the sewer, so only the water company's rate applies. The sewerage company bills nothing extra at all.
- An internal leak that drains away reaches the sewer, so both rates apply, each set by a different organisation.
- The share of the volume the sewerage company bills for, and where it applies its allowance, belongs to that company and not to the one supplying your water.
That last point is why this site records the sewerage basis against the sewerage provider rather than against the water supplier. A water-only company has no sewerage basis of its own, because it does not bill sewerage. how the sewerage half of the bill is calculated covers the two mechanisms and which companies use which.
What changes the answer
Three things, and the first is the one that catches people out.
- Which sewerage company actually serves your address. Three of the nine water-only areas span more than one sewerage company, so the supply area alone does not determine it.
- Whether the sewerage company has published a mechanism this site has read. Five of the eleven water and sewerage companies have not been read, and a water-only customer of one of those inherits an unknown rather than a default.
- The difference between the licensed company and the charges-scheme area. Four areas publish their own rates inside a larger licensed group, so the name on the licence and the name on the rate card can differ without anything being wrong.
None of this changes the volume of water lost, which is the same 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
The pairings above come from the consumer-facing supply area lists published by the water industry's own consumer and transparency bodies, rather than from the licence register, because the question a reader is asking is who bills them and not who holds the appointment.
One judgement in that is ours rather than anyone's publication: organising the site around the twenty areas that publish charges rather than the seventeen licensed companies. Both lists are real and published; the choice of which one a reader needs is a decision made here.
What to do next
Two things, and your bill answers both faster than any list can.
- Look at who the bill actually comes from. In a water-only area you may get two bills, or one bill collected by one company on behalf of both, and either way the two rates are itemised separately.
- Take the volumetric rate for water and the volumetric rate for sewerage as two separate figures. The calculators on this site apply them separately, because a leak can affect one without affecting the other.
Common questions
- Why do two companies bill me?
- Because supplying water and taking wastewater away are separate businesses with separate licences, and in some parts of England and Wales they were never combined. A water-only company supplies the water, and the regional water and sewerage company deals with what goes down the drain.
- Which of the two rates matters for a leak?
- Both, and in a specific order. The water rate always applies to leaked water. The sewerage rate applies only if the water reached the sewer, which a leak on the underground supply pipe never does. So an underground leak in a water-only area is billed by one company only, at one rate.
- My area lists more than one sewerage company. Which is mine?
- It depends where in the area you are, and only your bill can settle it. Affinity Water, SES Water and South East Water each span the boundaries of more than one sewerage company, so the pairing is geographic rather than fixed for the whole supply area.
- Is the licensed company the same as the one on my bill?
- Not always, and it does not matter for a leak. Four supply areas publish their own charges while sitting inside a larger licensed group, so the appointment and the rate card can belong to different names. The rate you pay is set by the charges scheme for your area, not by the group that holds the licence.