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Lebanon Plumbers, home

Leak Detection & Pipes

Slab Leak Repair

A leak under a concrete floor is worth finding accurately, because the difference between one small opening and a broken-up floor is entirely about location work.

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What is included

What this service covers

What we actually do on this job, and what you can expect us to deal with while we are there.

  • Locating leaks in supply lines under concrete floor slabs
  • Confirming a slab leak rather than groundwater or a waste leak
  • Rerouting the affected line to avoid breaking the slab
  • Opening, repairing and properly reinstating concrete where that is the better option
  • Repressurising and verifying the system afterwards
  • Advising on what the water may have done to what sits above it

Signs to look for

You may need this if you are seeing any of these

  • An unexplained warm area on a floor
  • Damp appearing at the edge of a slab or through flooring
  • The sound of running water with everything turned off
  • The water meter moving with no fixture in use
  • Flooring lifting, cupping or discolouring in one area
  • An unexplained jump in the water bill
  • Reduced pressure alongside any of the above

Why it happens

What usually causes it

01

Abrasion against concrete

A supply line that was not properly sleeved rubs against the slab as it expands and contracts with hot water, wearing through the wall over years.

02

Corrosion from the outside in

Soil chemistry and moisture attack copper in contact with concrete or fill, particularly where the line was laid without protection.

03

Ground movement

Settlement or shifting fill stresses a line that has no room to move, and the failure appears at the point of greatest strain rather than where the movement is.

04

Poor original installation

Joints buried in the pour, undersized or unsupported pipe, and lines run without sleeves are all found under slabs, and all of them shorten the life of the run considerably.

Our approach

How we handle this job

Specific to this work rather than a generic checklist bolted onto every page.

  1. 01

    Prove it is a slab leak

    Damp on a floor can be groundwater, a waste leak, or condensation, and those need different trades. Meter testing and isolating the supply confirm that pressurised water is escaping before anyone talks about concrete.

  2. 02

    Work out which line and where

    Hot and cold are isolated separately to identify the affected line, then the position is pinpointed acoustically and by temperature difference and marked on the floor.

  3. 03

    Compare rerouting against opening the slab

    Often the cheaper and less destructive answer is to abandon the buried section and run a new line through accessible space. Where breaking through is genuinely better we will say so.

  4. 04

    Repair, test and reinstate

    The system is repressurised and verified before anything is closed up, and any concrete we open is reinstated properly rather than patched.

Confirming it before touching concrete

The most expensive mistake on a slab leak is breaking up a floor to chase something that was never a slab leak.

Damp appearing at floor level has several possible sources, and they need different trades. Groundwater pushing up through or under a slab in wet weather is a drainage and waterproofing problem. A failed waste line is different again. Condensation on a cold floor in a humid basement is neither.

The test that separates them is the meter. A slab leak is pressurised supply water escaping, so with every fixture off, the meter keeps moving. Groundwater does not register on it at all. We run that check before recommending anything.

A plumber using acoustic listening equipment on a tiled floor to trace a hidden water leak

Why we usually reroute rather than dig

When a supply line under a slab has failed, the instinct is to open the concrete and repair the pipe. Often that is the worse option.

Abandoning the buried section and running a new line through accessible space, a basement ceiling, a wall cavity or an attic depending on layout, means that stretch of pipe can never fail again and the new run can actually be inspected in future. It also avoids the cost and mess of breaking and reinstating concrete.

It does not suit every property. Where the geometry makes a reroute impractical, or where the run is short and accessible, opening the slab is the right answer and we will say so.

Red and blue PEX tubing being laid in a grid across a concrete slab for radiant floor heating

Newer housing, mostly

Slab leaks turn up more in the postwar and later construction around Palmyra, Annville and the townships than in the older Lebanon city rowhomes, simply because slab-on-grade construction and supply lines run under concrete are a more modern arrangement. The older stock tends to have full basements with accessible pipework, which brings different problems and is covered under pipe repair.

Questions

Slab leak repair questions

Specific to this job. Every service page here has its own, none repeated.

General FAQ

Common questions

What exactly is a slab leak?
A leak in a water supply line that runs underneath or within a concrete floor slab. It matters more than an ordinary leak for two reasons: nothing about it is visible until the water has travelled far enough to surface, and water moving through the fill under a slab undermines what the slab is sitting on. They are worth acting on promptly rather than monitoring.
How would I know I have one rather than a normal leak?
The distinctive sign is a warm patch on the floor, which happens when the failure is on the hot line and is fairly conclusive. Others are damp appearing at the edge of the slab or coming up through flooring, the sound of running water with everything off, flooring cupping or lifting in one area, and a meter that keeps moving with nothing in use. Any one of those with a running meter is worth investigating.
Do you have to break up my floor?
Not always, and it is the first thing we try to avoid. In many cases the better answer is to abandon the section under the slab and reroute a new line through accessible space such as a basement, a wall cavity or an attic. Whether that works depends on the layout and the length involved. Where the run genuinely has to be accessed in place, we open the smallest area the repair allows and reinstate it properly.
Is rerouting as good as repairing the original pipe?
For most houses it is better. The buried section is abandoned rather than repaired, so that stretch of pipe can never fail again, and the new line runs somewhere it can actually be inspected and serviced in future. It also avoids the disruption and the reinstatement cost of concrete work. The main constraint is whether a sensible accessible route exists.
How much damage will already have been done?
It depends entirely on how long it has been running, which is often longer than people think. Water under a slab moves through fill, can undermine sections of it, and finds its way into flooring, subfloor and the base of walls. We will tell you what we can see. Assessing structural or flooring damage properly is a different trade, and if it needs one we will say so rather than guess.
Will insurance cover a slab leak?
Policies commonly cover sudden accidental discharge and the resulting damage, and commonly exclude gradual seepage, which is awkward because slab leaks are usually gradual by nature. Many policies also treat the cost of accessing the pipe differently from the cost of repairing it. Your policy is the only thing that answers this. We can document what we found factually for a claim.
Could it be groundwater rather than a leak?
Quite possibly, and it is a genuinely common confusion, particularly on properties near a watercourse. The distinguishing test is the meter: a slab leak is pressurised water leaving your system, so the meter moves with everything off. Groundwater does not touch the meter, tends to follow heavy rain, and is a drainage and waterproofing problem rather than a plumbing one. We check that before recommending any work.

Related services

Where we cover for this

All service areas

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Need slab leak repair in Lebanon County?

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