Water Meter Installation: WRAS-Approved Meters, Smart Meters, Sub-Metering for HMOs and Shared Supply Connections

Summary

Water meter installation falls into three distinct scenarios: a water company installing or replacing its own primary supply meter (outside the plumber's scope), an occupant requesting a primary meter where their property is currently unmetered (arranged through the water company), and sub-metering on private pipework within a building or across a shared supply. Plumbers are most commonly involved in the third scenario — fitting sub-meters to apportion water consumption across multiple units, measure consumption for billing disputes, or comply with freeholder requirements in HMOs and managed properties.

WRAS (Water Regulations Advisory Scheme) approval is mandatory for all fittings and meters installed on the water supply — including sub-meters. Using a non-WRAS-approved meter is a breach of the Water Supply (Water Fittings) Regulations 1999 and could result in enforcement action by the water company, loss of insurance, or liability for contamination. In practice, most professional-grade residential and commercial meters from established manufacturers are WRAS-approved, but always verify before purchase.

Smart metering is a growing requirement. Thames Water, Anglian Water, and several other UK water companies are mandating smart meters (meters with an automated meter reading transmitter) on all new connections and meter replacements. Some housing developers specify AMR-capable sub-meters to allow remote monitoring of individual units. Understanding the AMR options and whether they are required adds value when quoting for HMO and multi-unit developments.

Key Facts

• WRAS approval — all meters must appear on the WRAS product approval database; check at wras.co.uk
• Water Fittings Regulations — Water Supply (Water Fittings) Regulations 1999 cover all fittings on private pipework; meters are fittings
• Primary meter — belongs to the water company; installed at or near the boundary; plumbers do not install this
• Sub-meter — installed by a plumber on private pipework; owner's responsibility
• Meter size (residential) — DN15 (15mm) for most residential properties; DN20 or DN25 for larger demand
• Flow rate (DN15) — nominal flow Qn 1.5 m³/h; maximum flow Qmax 3 m³/h
• Meter accuracy — Class B or Class C to BS EN ISO 4064; ±5% error at low flows, ±2% at nominal flow
• Installation orientation — most meters specified for horizontal installation; some approved for vertical (check manufacturer)
• Isolating valves — isolation valve required upstream and downstream of every meter for maintenance
• Non-return valve — required downstream of sub-meters in HMOs to prevent back-siphonage between units
• AMR (Automatic Meter Reading) — pulse output or radio transmitter attached to meter; enables remote reading
• Pulse output — typically 1 pulse per litre; connects to a data logger or building management system
• MID approval — for commercial billing, meters should also carry MID (Measuring Instruments Directive) approval alongside WRAS
• Shared supply — where one supply pipe serves multiple properties, the pipe is maintained jointly by all connected parties; sub-metering does not alter this liability
• HMO licensing — local authority HMO licensing conditions may specifically require individual utility sub-metering

Quick Reference Table

Detailed Guidance

WRAS Approval and Product Selection

The WRAS database (wras.co.uk/product-approvals) lists all UK-approved water fittings. When selecting a meter:

1. Search the database by product type or manufacturer
2. Confirm the approval status is current (not expired)
3. Verify the approval covers the intended installation method (horizontal/vertical/angled)
4. Note the approval certificate number — record this on the job documentation

Commonly specified WRAS-approved meter brands in the UK include Elster (now Honeywell), Sensus, Apator, and Kent (Watermaster). Many of these are available from national plumbing merchants; budget around £30–£80 for a DN15 residential sub-meter, more for AMR-equipped units.

Sub-Metering in HMOs

Houses in Multiple Occupation (HMOs) with a single water supply frequently use sub-metering to:

• Charge tenants individually for water consumption
• Identify excessive use or leaks in individual units
• Comply with HMO licensing conditions
• Provide data for environmental reporting

Design principles for HMO sub-metering:

The cold water supply enters the building and passes through the landlord's main isolating stopcock. From this point, sub-meters are installed on the branches serving each unit. A common arrangement:

Rising main → cold water manifold (in plant room or cupboard) → individual branch per unit → sub-meter → unit stopcock → unit supply

Each sub-meter should have:

• Upstream isolating valve (quarter-turn ball valve, WRAS-approved)
• The meter itself (WRAS-approved, correctly oriented)
• Downstream non-return valve (check valve) — prevents back-siphonage between units
• Downstream isolating valve

All meters should be accessible without disturbing other tenants' supplies — typically in a communal locked cupboard, basement plant room, or within the individual unit under an access panel.

Cold water temperature: all pipework in HMO cold water distribution must be kept below 20°C to minimise Legionella risk. Route away from heat sources and consider lagging in warm plantrooms.

AMR and Smart Sub-Meters

AMR (Automatic Meter Reading) eliminates the need for physical meter reading. There are two main approaches:

Pulse output meters: The meter outputs one pulse per litre (or per 10 litres). A pulse data logger collects the counts and can be read locally via cable or remotely via mobile network. Cost-effective for HMOs — one data logger per building, one pulse input per meter. Total BMS cost per meter: £20–£50 for a pulse transmitter module; data logger costs vary from £100–£500 depending on functionality.

Radio AMR (WM-Bus): Some meters have an integrated radio transmitter (typically 868MHz) broadcasting consumption data that can be received by a handheld reading device (walk-by reading) or a fixed gateway. These are the same technology used by water companies for domestic smart meters. More expensive (£80–£200 per meter) but zero wiring — useful in retrofit situations.

Integration: AMR data can be displayed on a building management system (BMS), tenant portal, or landlord dashboard. Several SaaS platforms (e.g., Utilitec, Verv) offer metering-as-a-service with billing integration for HMO landlords.

Shared Supply Connections

Where one supply pipe serves multiple properties (common in Victorian terraces and older housing), the situation is:

• The water company owns the connection from the water main to the boundary
• The shared section of supply pipe from the boundary to the first junction is jointly owned by all properties connected to it
• Each property is individually responsible for their section from the first junction

A sub-meter on a shared supply measures consumption at that point — it does not change the legal ownership of the pipe. If you are asked to install a meter on a shared supply, check:

1. Whether all connected parties consent (they should — they are collectively responsible for the pipe)
2. Whether the meter size is adequate for the combined demand of all connected properties
3. Whether the water company has any specific requirements for shared supply metering in their area

Do not install a sub-meter in a way that would allow one property to isolate the supply to others without consent — this is likely unlawful interference with the supply.

Installation Best Practice

Key installation steps:

1. Isolate supply at the boundary stopcock or closest isolating valve
2. Cut the pipe at the chosen location — leave enough length for connections without excessive strain
3. Fit upstream isolating valve
4. Connect meter in correct flow direction (flow direction arrow is marked on meter body)
5. Fit downstream non-return valve (for sub-metering applications)
6. Fit downstream isolating valve
7. Pressure test before commissioning
8. Flush through and check for leaks
9. Record serial number, location, installation date, and initial reading

Pipe material: if connecting a meter between dissimilar metals (e.g., copper and MDPE plastic), use appropriate connectors to avoid galvanic corrosion. Dezincification-resistant (DZR) brass fittings are recommended where chlorinated water is present.

Frequently Asked Questions

Can I charge tenants for water based on a sub-meter reading?

Sub-metering for charging purposes is legally permissible in England and Wales for private landlords, subject to the meter being accurate and the charging arrangement being set out in the tenancy agreement. Ofwat does not regulate sub-metering by private landlords. However, be aware that some tenants may challenge sub-metered charges if the meter accuracy is disputed — use MID-approved meters for billing applications and retain calibration records.

What happens if a sub-meter fails?

A failed meter under-reads or stops counting. The standard approach is to estimate consumption based on average use during the period the meter was recording correctly — similar to how water companies handle faulty meters. Replace the meter promptly. If AMR monitoring is in place, a sudden drop to zero flow can flag a meter failure automatically.

Does the water company need to know about sub-metering?

You should notify the water company if you are installing a sub-meter on a shared or communal supply. For internal sub-metering within a private building (e.g., HMO), notification is not generally required, but the installation must comply with Water Fittings Regulations. Some water companies include sub-metering guidance in their developer services documentation — check the local supplier's technical standards.

Are there grants available for HMO sub-metering?

Some local authorities and water companies offer grants or subsidies for metering installations that reduce overall water consumption. This is particularly the case in water-stressed regions (southeast England). Check with the local water company's developer services team before quoting — a grant could improve the customer's business case.

Regulations & Standards

• Water Supply (Water Fittings) Regulations 1999 — statutory requirements for all water fittings, including meters, on private pipework

• BS EN ISO 4064:2017 — Meters for cold potable water; accuracy classes and testing

• Measuring Instruments Directive (MID) 2004/22/EC (retained in UK law) — for meters used in commercial billing

• Water Industry Act 1991 — water company responsibilities and shared supply arrangements

• WRAS Water Regulations Guide — technical guidance on compliance

• WRAS Product Approvals Database — check WRAS approval status for specific meters

• Ofwat — water industry regulator; metering policy

• CIPHE Water Fittings Regulations Guide — plumbing industry guidance

• Water UK — industry body; smart metering rollout information

• legionella management — cold water temperature management in HMOs

• cold water storage — cold water storage and distribution in multi-unit buildings

• outside tap installation — WRAS requirements for external connections

• pipe sizing — pipe sizing for shared and multi-unit supplies