Water Supply

Water supply covers drinking and service water from the utility connection to the outlets: the incoming main and meter, backflow prevention devices that stop building water flowing back into the public supply, pressure-limiting valves, storage and break tanks, distribution pipework, risers and isolation valves, sub-meters, and cold water to fixtures and equipment. Hot water plant and booster pumps have their own pages.

In apartment and commercial buildings, water often passes through break tanks and booster pumps before reaching upper floors. Tenancies and apartments are sub-metered, and the owner's infrastructure stops at each lot's isolation valve or meter. Where a building has cooling towers, irrigation, fire services or process water, backflow devices separate each hazard from the drinking supply.

What shortens life:

• Aggressive water chemistry that pits copper, dezincifies brass and corrodes steel.
• High pressure without limiting valves, which stresses joints and fittings and causes water hammer.
• High velocity in undersized pipes, causing erosion at bends and fittings.
• Stagnation in tanks and dead legs, which affects water quality.
• Ground movement on buried services.

Internal corrosion

Galvanised steel corrodes from the inside: the zinc is consumed, the steel rusts and builds tubercles that narrow the bore, flow falls, and water runs brown after periods of no use. Copper can pit in certain waters, producing pinhole leaks that recur along the same runs. Brass fittings in plastic systems can lose zinc (dezincification), becoming porous and weak, and leak or fail.

Backflow and cross-connection

Where building water connects to a hazard (cooling towers, fire systems, irrigation, laboratories, chemical dosing, boilers), a drop in mains pressure can draw contaminated water back into the drinking supply. Backflow devices prevent it only if they work; devices that are not tested can fail open without any sign. Unprotected cross-connections created by alterations are a public health risk.

Pressure problems

High mains pressure without limiting valves bursts flexible hoses, wears tap washers and valves, and causes water hammer: the banging when valves close fast, which loosens supports and fatigues joints. Low pressure at upper floors points to booster problems, undersized risers or corroded pipes.

Storage tank contamination

Cold water storage tanks with poor lids, missing insect screens and sediment build-up allow contamination; warm tanks in roof spaces and plant rooms grow Legionella. Tanks that are oversized for current use hold water too long.

Lead in drinking water

Lead service pipes and lead solder in older plumbing release lead into water, especially after it has stood. In the United States, federal rules now require lead service lines to be identified and replaced; in Britain, water companies and owners share responsibility for lead pipes on either side of the boundary.

Hidden leaks

Leaks under slabs, in walls and in ceiling voids waste water, damage finishes and structure, and are found through rising consumption or damp. Polybutylene and failed fittings are common sources.

Seized isolation valves

Valves never exercised seize, so a leak on one floor means shutting down the building. This turns small repairs into major outages.

On site

• Pipe materials visible in plant rooms, risers and under fixtures.
• Brown water on opening taps; low flow at upper floors or far outlets.
• Water hammer noise; loose pipe supports.
• Green or white crusting on brass fittings (dezincification).
• Backflow devices: test tags, leaks from relief ports, bypasses.
• Tank lids, screens, overflows and condition.
• Damp and staining on walls and ceilings near pipe runs.

In the records

• Water consumption trends, especially night-time use.
• Backflow device register and test certificates.
• Leak and repair history by location.
• Water quality testing, including lead where relevant.
• Tank cleaning and inspection records.

Findings are graded by what they demand: safety (can hurt someone now), failure (failed and damaging the building), condition (distress present and progressing), lifecycle (renewal due on age and exposure), deadline (a regulator or ordinance sets the date), check (investigate before sizing works) and nil (cosmetic or stable).

A hydraulic engineer or licensed plumber leads, with a water treatment specialist where corrosion or quality is in question.

• Materials survey of incoming services, risers, branches and fittings.
• Backflow audit: every hazard connection identified, with the device type checked against the hazard rating and tested.
• Pressure and flow measurement at the incoming main, at the top floors and at remote outlets.
• Water quality testing: lead and copper at outlets after standing; Legionella and bacterial counts in storage.
• Pipe sampling: remove sections of corroded or leaking pipe for examination.
• Leak detection: meter tests, acoustic and thermal methods for hidden leaks.
• Tank inspection: internal condition, lids, screens, temperatures.
• Valve operation: exercise isolation valves and record those that fail.

The report should state pipe materials and condition, backflow compliance, pressure and flow adequacy, water quality, leaks and a replacement strategy.

• Backflow: install or upgrade devices to suit each hazard, and set up annual testing.
• Pressure control: pressure-limiting valves and water hammer arrestors.
• Replacement of galvanised, polybutylene and pitting copper pipework, riser by riser with temporary supplies.
• Fitting replacement with dezincification-resistant brass.
• Lead removal: replace lead service pipes and remove lead solder where testing warrants.
• Tank works: clean, reline, fit sealed lids and screens, or remove redundant tanks.
• Valve replacement so floors and risers can be isolated individually.
• Leak repairs and smart metering to find future leaks quickly.

• Water quality management: flushing programmes for little-used outlets and dead legs, and removal of redundant branches so water does not stagnate.

Backflow testing recurs annually per device; device replacement is per device. Pipe replacement is priced by length or per riser, with access, finishes and temporary supply as major components in occupied buildings. Valve replacement is per valve. Tank works are lump sums. Lead service line replacement is a lump sum and may be shared with the utility under its programme.

Backflow and water quality compliance are code compliance; pipework replacement is lifecycle; repairs are repairs and maintenance.

• Australia. AS/NZS 3500.1 governs water services and backflow prevention, with testing of devices under AS 2845.3 typically required annually by the water utility; plumbing work is licensed and certified in each state; pressure-limiting valves are required where mains pressure is high.
• United Kingdom. The Water Supply (Water Fittings) Regulations 1999 (and Scottish byelaws) govern fittings and backflow protection, with WRAS approval of products; the HSE Approved Code of Practice L8 covers Legionella control in cold water systems; water companies and owners have lead pipe replacement responsibilities on either side of the boundary.
• United States. The International and Uniform Plumbing Codes govern water supply; states and utilities run cross-connection control programmes with annual testing of backflow assemblies; the EPA's Lead and Copper Rule Improvements require water systems to replace lead service lines over the coming decade.

• Backflow device register and test certificates.
• Water consumption data, ideally by sub-meter.
• Leak and repair history.
• Water quality test results, including lead where relevant.
• Tank cleaning and Legionella records.
• Hydraulic drawings showing pipe materials and isolation.
• Utility notices about lead pipes or backflow.

• Pressure readings at the incoming main and upper floors.