Water Mains & Supply Pipe — London & Surrey

Water Mains & Supply Pipe Leak Investigation

Leaks on external mains and private supply pipes hide under drives, gardens and concrete. We match the right method to the pipe and prove where the water is going — with evidence your insurer can work with. Fully insured and qualified specialists.

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Whose pipe is it?

The water company is usually responsible up to the boundary (typically the outside stop valve); the supply pipe from the boundary into your home is normally the owner’s responsibility. Water companies’ assistance schemes vary — check yours. When it’s on your side, this is the service you need.

Underground supply pipe exposed during a DML mains leak investigation.

The methods — what each proves, in plain English

Acoustic detector / listening stick

Water stays under normal pressure. Confirms leak noise at a fitting, pipe or surface. Best for indoor plumbing, exposed pipes, stopcocks and first checks. Limitation: only checks where the microphone is placed.

Corroded joint with verdigris — identified as the leak source.

Ground microphone

Water stays under pressure. Finds the loudest surface point above the leak. Best for outside mains under concrete, driveways, tarmac and soil. Limitation: plastic pipes, deep pipes and soft ground transmit less sound.

Correlator

Water stays under pressure. Calculates where between two sensors the leak noise originates. Best for longer underground mains with accessible valves or fittings. Limitation: needs correct pipe route, material, diameter and length.

Tracer gas (5% hydrogen / 95% nitrogen)

Water is drained and replaced with a safe tracer gas; a detector finds hydrogen escaping through the ground. Best for plastic pipes, quiet leaks, concrete, soil and drained systems. Limitation: more setup — gas cylinder and specialist detector required.

Nitrogen pressure testing

Water drained; nitrogen pressurises the pipe. Proves pressure loss and may generate audible noise. Best for dry pressure testing and sound detection. Limitation: a hydrogen detector cannot find nitrogen — this proves loss, not surface position.

Compressed air pressure testing

Water drained; regulated air pressurises the pipe. Proves pressure loss and can make a leak hiss. Best for small isolated sections where sound can be detected. Limitation: leaves no detectable tracer above ground.

Potable-water CCTV

A hygiene-controlled camera physically enters the pipe: joints, bends, obstructions, pipe changes, damage — sometimes the leak opening itself. Best for difficult service pipes, poor pressure and repeated failures; insurers sometimes ask for internal footage where suitable. Limitation: needs access and hygiene control; not suitable for every pipe or every pinhole.

In-line acoustic tool

A sensor travels inside a live main and detects the leak from very close range. Mainly for larger commercial or water-company mains. Limitation: specialist contractor/utility service, not normal domestic kit.

What you get

The method(s) used and why, the evidence (readings, traces, footage where used), the suspected leak position, minimum access recommendations, and repair recommendations — insurance-ready, prepared to support your claim. Works are quoted based on the job.

Book a mains / supply pipe investigation

📞 Call free: 0800 054 1524
💬 WhatsApp: 07733 019492
Or send the form below. London & Surrey.