Skip to content
Plumbing guide

Leak Detection and Repair: How Hidden Leaks Are Found

Not every leak is obvious. Some show up as a bill that jumped for no reason, a musty smell in a corner, or a stain on a ceiling below a bathroom. Leaks that are left alone rarely stay small. This guide covers how leaks are found, what causes them, and what a proper repair looks like.

Signs of a hidden leak

  • Water bill increased with no change in usage
  • Damp spot, discolouration, or bubbling paint on a ceiling or wall
  • Musty smell in a bathroom, kitchen, or basement
  • Warm spot on a floor slab, sometimes a hot-water line leak
  • Water meter dial moves while everything in the house is off

Where leaks usually start

  • Supply line fittings under sinks and behind toilets
  • Pinhole corrosion in older copper pipe
  • PEX fittings that were over-crimped or installed cold
  • Wax seals under toilets that have failed
  • Water heater fittings and the T&P valve
  • Shower valves and tub spout diverters leaking behind tile

How a plumber locates a leak

Visual inspection first. Then targeted moisture checks with a meter. For pressurized systems, isolating a section of pipe and watching for pressure drop tells us whether the leak is on the supply side. Acoustic listening and thermal imaging help narrow down leaks inside walls or under slabs before any drywall is opened.

What a repair usually involves

  • Smallest reasonable access point to expose the leak
  • Repair scope confirmed before opening anything larger
  • Section replacement matched to existing material, copper or PEX
  • Pressure test after repair before closing up
  • Drywall and finish repair usually handled separately by a finish trade

Need a plumber?

A specialist assesses the problem on site before any repair work is priced. Repair options and pricing are explained before approved work begins.

Frequently asked questions

Will you have to open walls or ceilings?+

Only when the leak is inside them, and only as much as needed. We locate first, then open the smallest reasonable access.

Are pinhole leaks in copper a sign the whole system is failing?+

Not always. Water chemistry, age, and pipe run can all cause localized corrosion. Repeated pinholes in different spots suggest broader replacement is worth costing out.

More plumbing guides

Get a plumber in Mississauga on the way

Call for immediate help, or send us your details and a plumber will follow up to confirm scheduling based on urgency and availability.

  • Phone
    (647) 933-5376
    Fastest response, tap to call
  • Service area
    Mississauga and surrounding Ontario, see our other locations for adjacent cities.
  • Hours
    Open 24 hours, 7 days a week

Request a Plumbing Service Call

A plumber must inspect the issue on site before providing repair options and pricing. This helps ensure the problem is diagnosed accurately before work is recommended.

Short descriptions are fine. A plumber will confirm the details on the phone.

Your info is used to reach you about your service request.