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Mains leak under a front doorstep found in Kensington

A water meter was turning with no water in use. Tracer gas pointed to the front door, and a ground microphone, first on the mat and then inside the floor void, placed the leak just under the concrete step outside, where a failed 32mm fitting was replaced.

Silver and red ground microphone on a doormat inside a front door, with the engineer holding its handle
Silver and red ground microphone on a doormat inside a front door, with the engineer holding its handle

Signs of the leak in Kensington

The outside water meter recorded about one litre every five minutes with no water in use. The heating was holding pressure normally, so the loss was on the incoming cold supply. With 2 bar applied, the supply pressure fell to zero within five minutes.

How acoustic equipment found it

With tracer gas showing inside the front door, the engineer listened with a ground microphone on the mat and heard leak noise in that area. After lifting the access panel into the floor void, the sound was stronger but pointed slightly further out, under the concrete step, which is where the leak was.

The investigation, step by step

  1. 01Checked the outside meter: about one litre every five minutes with no water in use.
  2. 02Pressure tested the incoming supply from under the kitchen sink; 2 bar fell to zero within five minutes.
  3. 03Put tracer gas into the supply; readings showed around the inside of the front door.
  4. 04Listened with a ground microphone on the doormat and heard leak noise.
  5. 05Removed the skirting and lifted the access panel; in the void the sound was stronger but pointed under the concrete step.
  6. 06With the customer's consent, broke out the tile and concrete of the step and found a leaking 32mm fitting.
  7. 07Replaced the fitting; pressure then held and the meter stood still.
  8. 08Refitted the access panel and screwed down the joists.
Threshold opened up with floor joists visible and the supply pipe and fittings exposed in the broken-out concrete below
Threshold opened up with floor joists visible and the supply pipe and fittings exposed in the broken-out concrete below
New white and blue compression fittings on the supply pipe in the dug-out ground under the step
New white and blue compression fittings on the supply pipe in the dug-out ground under the step

What was found

Found
A leaking 32mm fitting on the incoming cold supply, inside the concrete front doorstep. Water staining on the joists in the floor void showed it had been leaking for some time.
Repair
The fitting was replaced with new 32mm and 25mm fittings and 32mm pipe. The supply then held pressure and the meter was stationary. The access panel was refitted and the joists screwed down.
Recommended afterwards
While the area is open, upgrade all the fittings in that section. The concrete step needs reinstating by a separate tradesperson.
Worth knowing
The concrete step was not reinstated as part of this visit.

Another ADI customer, on a different job

“Robert attended and carried out both tracer gas and acoustic testing, and was able to locate the leak quickly and accurately.”

Heather L., Trustpilot review, 30 April 2026

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