Start from the right question
People ask why their underfloor heating pipe failed. Almost always the better question is what happened to it. Modern barrier pipe, PE-X or PE-RT with an aluminium or EVOH oxygen layer, is rated for decades at heating temperatures and pressures. Buried in screed, protected from UV and untouched, it does not simply give up after eight years. Something got to it.
That matters for you in a practical way. A pipe that failed at random could be leaking anywhere in a 100-metre loop. A pipe that was damaged failed where the damage happened, and damage happens in places that repeat from job to job. That is what turns a whole-floor problem into one access hole.
The four things that actually damage buried UFH pipe
1. A fixing driven through the floor
This is the most common cause we attend, and it is usually not the heating installer's fault. The screed goes down, the pipe disappears, and then months or years later another trade fixes something to the floor. A carpenter pinning skirting through the screed edge. A kitchen fitter anchoring a plinth or an island. A flooring contractor screwing down a batten or a threshold strip. Someone bolting a shower tray, a stair spindle, a radiator bracket at floor level.
Two things follow from this. First, a screw through a pipe often does not leak immediately — it plugs the hole it made. The system holds pressure for weeks or months while the fixing corrodes or works loose, then the loss starts and nobody connects it to work done last year. Second, the leak is at a fixing, which means it is at the edge of a room, at a threshold, or under a fitted unit. That is a small search area.
2. A kink left in at installation
PE-X and PE-RT tolerate being bent, but only to the manufacturer's minimum radius. Pulled too tight around a corner or into a manifold, the pipe kinks. Most kinks are noticed and cut out. The dangerous one is the kink that was partially straightened and laid anyway: the outer wall of the bend is stretched thin and the material is stressed, and it is then buried under screed where nobody will ever look at it again. It can hold for years and fail under thermal cycling.
Kinks happen where the pipe is forced to change direction fastest, which is at the tight turns of the loop and at the manifold entry.
3. Laid against something sharp, or straight across a movement joint
Screed is not soft. A pipe pressed against a sharp aggregate edge, a cut clip rail, a rough construction joint or the raw edge of an insulation board sits under point load every time the floor is walked on and every time the pipe expands and contracts with temperature. Over years that abrades or slowly cuts the wall.
The related fault is a pipe crossing a movement or expansion joint without a sleeve. The joint exists so two bays of screed can move independently. A pipe passing through it unprotected gets worked at that exact line, back and forth, for the life of the floor. When it fails, it fails on the joint — which is a straight line you can see on a plan or find with a crack detector, not a random point in a room.
4. Oxygen ingress on older, non-barrier pipe
This one is different, because the pipe itself is not usually what leaks. Plastic without an oxygen barrier lets oxygen diffuse through the wall into the system water. That oxygen corrodes the steel and cast iron elsewhere in the system — the boiler heat exchanger, radiators, pump housings, manifold bodies. You get black sludge, cold spots, and pinholes on metal parts while the plastic stays intact.
So on a floor laid before barrier pipe was standard, or on a DIY-extended loop run in non-barrier pipe, the leak that empties the system is often at a corroded manifold fitting or a steel component, not in the screed at all. Ruling that in or out early is worth an hour, because it is the difference between lifting a floor and not.
Why the damage sits in predictable places
Put the four causes together and the map is fairly consistent. Before anyone attends, these are the places worth thinking about first:
| Where | Why it concentrates there |
|---|
| Doorways and thresholds | Every loop has to pass through, so pipe density is highest; threshold strips, door frames and floor fixings all land here. |
| Manifold entry | Tightest bends in the whole system, plus mechanical strain from the manifold itself and from anything fixed to that cupboard. |
| Room perimeters | Skirting fixings, kitchen and utility unit plinths, radiator brackets, stair bases. |
| Movement and construction joints | Designed to move; anything crossing them unsleeved gets worked until it fails. |
| Under fitted furniture and appliances | Installed after the floor, fixed down, and then never looked at again. |
What this does not mean is that anyone should cut on a hunch. It means the sweep starts where the odds are, and that a positive reading in one of those places is easier to trust.
What the symptoms narrow down before we arrive
A falling gauge with one loop that never reaches temperature points at that loop, under the screed. A falling gauge with every loop heating evenly more often points at the manifold, the fill point or the boiler side — all reachable without touching the floor. A patch of floor that stays warm hours after the heating has gone off is a hot pipe losing water into the screed around it. That symptom triage is covered on the underfloor heating leak page; this page is about what comes next.
How one patch of floor gets opened instead of a room
- Isolate and pressure test. Each loop is shut at the manifold and tested separately. This proves the loss is real, sizes it, and — more usefully — tells us which single loop is losing. On a six-loop floor that has already removed five sixths of the area.
- Thermal imaging over the live loop. With the loop running, the camera reads the pipe layout straight off the floor surface. That gives the actual serpentine route rather than a guess, and a leak losing hot water into screed often shows as a bloom that sits off the pipe line.
- Drain and charge with tracer gas. This is the step that matters on plastic pipe. Screed kills leak noise and plastic attenuates what is left, so acoustic detection struggles here. A 5% hydrogen, 95% nitrogen mix escapes through the same hole the water was finding and rises through the screed and grout to a probe on the surface. How tracer gas works, and what defeats it.
- Confirm the peak, then cut. One reading is not a result. The engineer works outwards until the signal falls away on both sides, airs the room, and re-tests. The floor is opened at the confirmed point — typically a hole of a few hundred millimetres, not a lifted floor.
Repair the pipe, or re-run the loop
A single damage point in sound pipe is a coupler repair: cut out the damaged section, join with a proper compression or press fitting rated for burial, pressure test, re-screed. Where the pipe is old non-barrier, or where the same loop has already been repaired more than once, patching it again is money spent on a system that wants re-running — and we will say so rather than book a second visit for the same floor. In some rooms the honest answer is a new loop run in the floor build-up or, on a small area, a surface re-route.
The floor then goes back. Screed, tile, board and decoration are reinstated by our own handymen and builders, so you are not left with an open hole and a list of other trades to chase. See underfloor heating leak repair for how the job runs end to end.
Cost, and the report
Detection and repair are charged at £150 per hour, agreed before we attend, with no call-out fee. If we do not find the leak, you do not pay for the time spent looking. The visit includes a written report setting out what was tested, what was found and what had to be opened to reach it, which is the document a trace-and-access claim is assessed on. Whether the policy pays is the insurer's decision, not ours — the report exists so that decision is made on evidence. Full rates are on pricing.
When it is not the UFH pipe
Worth ruling out before a floor is touched: a failed expansion vessel, which drops pressure on cooling without losing a drop of water; a passing pressure relief valve dumping to the discharge pipe outside; a weeping manifold union or actuator seal inside the cupboard; and, in flats, a leak from above soaking the screed from the top down. All four look like an underfloor leak on the gauge or on a damp meter, and none of them is a reason to cut a floor.
