Diagnose a plumbing leak.

Plumbing leak diagnosis in the UK typically costs £90–£300 for the inspection visit, plus repair costs. Most leaks are routine and fixable in a single visit. Hidden leaks (in walls, under floors, in cavities) require specialist diagnostic equipment — thermal cameras, moisture meters, acoustic detectors — and may run £200–£600 for the diagnostic phase alone.

The typical leak diagnostic process: visual inspection, pressure testing, isolation testing (turning off zones), and specialist tools where the leak isn't immediately visible. Most leaks are surprisingly simple once located — finding them is the skill.

Typical UK leak diagnosis costs

Common leak symptoms and their likely causes

• Damp patch on ceiling — leak from above (bathroom, roof, water tank, central heating).
• Wet floor near appliance — washing machine, dishwasher, hot water cylinder, boiler.
• Increased water bill with no obvious cause — hidden leak, often slow but continuous.
• Wet wall internally — pipe in cavity, possibly a heating pipe.
• Wet wall externally — penetrating damp from outside, or main supply leak.
• Rust stain at radiator joint — pinhole leak, often near valve or connections.
• Damp smell with no visible water — slow leak somewhere; diagnostic survey needed.
• Boiler losing pressure repeatedly — leak somewhere in heating system, may be very small.

Diagnostic methods

• Visual inspection — first step always. Look for wet, stained, or discoloured areas.
• Meter test — turn off all taps for 30 minutes. Watch the water meter. Movement indicates a leak somewhere.
• Pressure testing — isolate sections of the plumbing system and pressurise. Pressure drop indicates leak.
• Moisture meters — handheld devices detect higher moisture in walls and floors.
• Thermal imaging — leaks (especially hot water) show as cold or warm spots compared to surrounding areas.
• Acoustic detection — specialist sensors hear water flowing through a leak; useful for buried pipes.
• Tracer gas — non-toxic gas (typically hydrogen / nitrogen mix) introduced into the system. Detector locates where it escapes. For hard-to-find leaks.
• Camera survey — for drains specifically, a small video camera traverses the pipe.

Things people often miss

• Insurance cover — many UK home insurance policies include "trace and access" cover for leak detection. Check before paying for diagnostic work yourself.
• Stop the leak first — for active leaks, turn off the relevant supply at the stop tap before searching for the source.
• Document for insurance — photos of damp patches, water marks, and meter readings build the claim case.
• Boiler pressure drop — repeated need to top up boiler pressure indicates a heating leak. Often a tiny pinhole somewhere; tracer gas detection often required.
• Old plumbing materials — copper pipes typically last 50+ years; lead pipes (pre-1970s) need replacement urgently. Plastic / PEX pipes vary by manufacturer and joints.
• Tracking down the source — water travels along joists and through cavities before showing on a ceiling. The visible damp patch may be metres from the actual leak source.

Frequently asked questions

Want a local pro to handle this? A plumber with leak detection experience and the right tools resolves most leak diagnoses in a single visit. For complex cases requiring specialist equipment, leak detection specialists work alongside plumbers and insurance loss adjusters.