How to find underfloor heating pipes in a floor (thermal imaging and other methods)

You might need to find the pipes for several reasons: to fix something to the floor without drilling into a loop, to trace a loop that has gone cold, to find a leak behind a pressure drop, or to plan where you can safely cut into a screed. Pipes in a screed are buried, and in board systems they sit under the floor finish, so you cannot see them. Guessing from the room layout is how most pipe damage happens.

This guide explains how to trace pipes with a thermal camera, what a leak or blockage looks like on screen, what to do if you do not have a camera, and when to call in a leak detection specialist. The same thermal method works for electric underfloor heating cables.

Can a thermal camera see underfloor heating pipes?

Yes, as long as the heating is running. A thermal camera reads surface temperature, and warm water in the pipes heats the floor directly above them more than the floor between them. The camera turns that difference into a picture of the pipe layout.

A test equipment specialist's guide says floors usually sit at room temperature, 18 to 21°C, and that hot pipes raise the surface above them by about 4 to 5°C. That is a big enough difference for even a basic camera to show clearly. Its worked example of an underfloor system read roughly 26°C directly over the pipes and 18°C as the floor average.

Camera feature	Recommended
Resolution, minimum	120 × 90 pixels
Resolution, ideal for most floors	160 × 120 pixels
Resolution, several floor layers or tight pipe	320 × 240 pixels
Thermal sensitivity	0.1°C (100mK) or better
Useful temperature range	15 to 30°C

The same source says higher-resolution cameras can show pipework under carpet and rubber underlay, and up to 90mm deep in a concrete screed. Cheap phone add-on cameras can work on a tiled screed floor, but they struggle where the pipe is deep or the floor finish insulates well.

How do I trace UFH pipes with a thermal camera?

Warm the floor fully, then follow each loop from the manifold. Scanning a floor that has only just started to warm gives a blurred image, so be patient.

1. Turn the heating up. Set the thermostats above room temperature so every zone calls for heat. Wait until the floor is fully warm. A screed floor takes far longer than an overlay board.
2. Trace one loop at a time if you need detail. Close the other loops at the manifold so only the loop you want is hot. This stops neighbouring loops blurring together. Note the flow meter settings before you close anything, so you can put them back.
3. Start at the manifold. Point the camera at the floor where the pipes leave the manifold and follow them through the room and back.
4. Use auto-ranging and a high-contrast palette. Auto-ranging adjusts the colour scale to the temperature spread on screen, so the pipes stand out.
5. Mark the floor as you go. Use masking tape or chalk on the pipe runs, or on the area you want to drill, so you have a record once the floor cools.
6. Photograph the result. Keep the images with your house records. They save time if anyone works on the floor later.

Afterwards, reopen the loops you closed and return each flow meter to its original setting. Our guide to flow meter settings explains how to read them.

What does a leak or blockage look like on a thermal image?

A leak shows as a blotchy warm patch, while a blockage or airlock shows as a pipe that fades out or disappears. The shape of the warm area tells you which one you have.

What you see	Likely cause
Clear, sharp warm lines	Normal, working pipe
A blotchy warm patch with a bright centre that fades into the floor	Leak, with hot water spreading into the screed
A gap where the pattern stops	Water not reaching that section: blockage, airlock or closed loop
Pipe colour fading towards room temperature along the run	Partial blockage, air in the loop or very low flow
Faint, poorly defined pipe outline	Heat going downwards, which can mean missing or poor insulation

A large difference between the return temperatures of loops at the manifold can also point to a leak, air or a fault in one loop. If one loop is simply cold, start with our guide to one UFH loop not heating before you suspect a leak.

If the system pressure keeps falling and you cannot see a leak anywhere at the manifold or boiler, a leak under the floor becomes more likely. Our guide to underfloor heating pressure dropping covers the checks to do first.

How can I find UFH pipes without a thermal camera?

Start with the records. Many installs have a loop drawing, photos taken before the screed went down or a labelled manifold, and these are often enough to keep a drill away from the pipes.

• Loop drawings. Ask the original installer or builder for the loop design. It shows each circuit, its spacing and the feed route to the manifold.
• Photos taken during the install. Check old phone photos or the builder's handover pack. Pipe on clips or panels is easy to see before the screed goes on.
• Manifold labels. Each port is usually labelled by room. This tells you which loop serves the room, though not its route.
• Feel the floor. With the heating fully warm and a bare tiled or stone floor, you can sometimes feel warmer strips by hand. It is rough, but better than nothing.
• Feed pipes. Pipes are packed most tightly near the manifold and in doorways where several loops run together. Treat those areas as no-drill zones.

If the job matters, such as drilling for a kitchen island or a WC, hire or borrow a thermal camera. It costs far less than lifting a floor to repair a loop.

How do professionals find a hidden UFH leak?

They use thermal imaging first, then tracer gas or acoustic equipment to pinpoint the exact spot. That keeps the area of floor they have to break out as small as possible.

• Tracer gas. The system is drained as far as practical, sealed and filled with a mix of 5% hydrogen and 95% nitrogen. Hydrogen is a very small molecule and rises through concrete and screed. A detector walked over the floor picks up the highest reading over the leak. The gas mix is non-flammable and non-toxic.
• Acoustic detection. Listening equipment picks up the sound of water escaping, but it needs the pipe to be under pressure and the leak to be noisy enough to hear. Tracer gas is used when it is not.
• Thermal imaging. Used to map the loops and narrow down the area before the other methods.

Once the leak is found, the screed is broken out over that spot and the pipe is repaired with a coupling. Our guide to repairing damaged underfloor heating pipe covers the repair. On multilayer pipe a press fit straight connector is the usual choice for a repair that will be buried again.

Can I find electric underfloor heating cables the same way?

Yes. A heating mat or loose cable warms the floor above it in the same way, so a thermal camera will show the cable runs once the system is on and warm. Isolate the circuit before doing anything to the floor.

A cold strip in an electric floor can mean a damaged cable. Do not cut into the floor to look for it. Testing and repairing electric UFH needs a qualified electrician, and the final connection must meet Part P and BS 7671. Our electric UFH fault finding guide explains the resistance and insulation tests an electrician will do.

What should I do after hitting a UFH pipe?

Stop, turn the heating off and isolate the loop at the manifold. Close both the flow and return valves for that loop so the rest of the system can stay in use while you arrange a repair.

1. Isolate the loop. Close the valves for that loop at the manifold and turn off the boiler or heat pump demand.
2. Contain the water. Mop up and keep water away from electrics, including the wiring centre.
3. Expose the damage. Break out just enough screed or lift enough board to reach clean, undamaged pipe either side.
4. Repair and test. Fit a coupling, then pressure test the loop before covering it. A hydraulic test pump makes this easy.
5. Refill and bleed. Reopen the loop, top up the system pressure and bleed any air.

If you would rather not do it yourself, MaxHeatUFH passes installation and repair enquiries to vetted approved installers. Request an installer.

Frequently asked questions

How do I find out where my underfloor heating pipes are?

Turn the heating on until the floor is fully warm, then scan it with a thermal imaging camera. The pipes show as warm lines. If you have no camera, look for loop drawings or photos from the original install.

Can a thermal camera see pipes under carpet?

Often, yes, but you need a better camera. A test equipment specialist says higher-resolution models can show pipework under carpet and rubber underlay. Basic models work best on tiled or stone floors.

How deep can a thermal camera see into a screed?

A thermal camera only sees surface temperature, not into the floor. It works because the heat travels up. One source says better cameras can show pipes up to 90mm deep in a concrete screed.

Can I drill into a floor with underfloor heating?

Only once you know exactly where the pipes are. Trace and mark them first, keep well clear of the runs and stay away from the area near the manifold and doorways, where feed pipes are packed tight.

What thermal camera resolution do I need for underfloor heating?

160 × 120 pixels with 0.1°C sensitivity suits most homes. Use 320 × 240 pixels for floors with several layers or tightly spaced pipe.

Does a metal detector find underfloor heating pipe?

It is unreliable. Plastic pipe has no metal in it, and the aluminium layer in multilayer pipe is thin. A thermal camera with the heating on is far more dependable.

How do leak detection companies find UFH leaks?

They combine thermal imaging with tracer gas, a mix of 5% hydrogen and 95% nitrogen, or acoustic listening equipment. This pinpoints the leak so only a small area of floor needs breaking out.