Soil Pipe and Waste Pipe Leak Investigations
Waste leaks only run when a fixture is used, so they hide between events and get blamed on everything else. We reproduce them, trace them and document them.
Soil and waste pipe leaks are intermittent by nature: a toilet pan connector that weeps on every flush, a bath waste that drips when the bath empties, a cracked cast-iron stack behind boxing, or a shower trap that has lost its seal. Because the pipework is unpressurised, methods that rely on pressure, such as acoustic listening or tracer gas, are often not the right tools. DML uses a different approach for drainage-side leaks.
How we trace waste and soil leaks
- Controlled use testing of each fixture in turn, with moisture readings and thermal imaging below to catch the event.
- Dye testing to confirm which fixture is responsible when several share a route.
- Inspection cameras into boxing, voids and stacks, and CCTV drain surveys for below-ground sections.
- Joint and seal inspection of pan connectors, traps, waste fittings, stack joints and shower tray upstands.
- Ruling out supply-side and heating leaks, penetrating damp and condensation on cold pipes.
Common findings in London flats and houses
- Toilet pan connectors displaced or perished
- Bath and shower wastes with failed seals or cracked traps
- Cast-iron soil stacks corroded at joints behind boxing
- Cracked or disconnected underground drains near the property
- Macerator and pumped waste units leaking at connections
- Sink and dishwasher wastes pushed off under cupboard units
Report and repair
Your report identifies the fixture, the point of failure, photographs and readings, the health considerations where foul water is involved, and a repair scope. Repairs are quoted separately by our team or any plumber or drainage contractor. For leaks from a flat above, the report gives the freeholder or managing agent the evidence to act on.
We investigate across Greater London and Surrey. See areas we cover.
Frequently Asked Questions
Why does the leak only appear sometimes?
Because waste pipes only carry water when a fixture is used. We test fixtures one at a time to catch it.
Is a soil pipe leak dangerous?
Foul water leaks are a hygiene issue and should be dealt with promptly. Our report flags contaminated materials that should be removed rather than dried.
Can you find a leak in a stack inside a wall?
Usually, by camera inspection, dye testing and moisture mapping. We aim to open only the spot that needs repairing.
Is this covered by insurance?
Often, under escape of water and trace and access. See escape of water investigations.
Do you repair the pipe?
DML locates and reports. Repairs are quoted separately by our team or your own contractor.
Related services
Related reading: When you need a CCTV drain survey · Why a CCTV drain survey matters before you buy a house
Catch the intermittent leak
Independent soil and waste pipe leak investigations across London and Surrey.
Last reviewed: 23 October 2026. Independent investigation and written reports. Repairs are quoted separately.