Which UFH pipe coil length to buy: 100m, 200m or 500m?

UFH pipe is sold by the coil, not by the metre. That makes ordering a small puzzle. Buy coils that are too short and you end up with a pile of 30m offcuts that are too short to make a loop. Buy one huge coil for a small job and you pay for pipe you will never lay.

This guide shows how to turn your loop lengths into a coil order, which coil sizes we stock in each pipe, and when a 100m, 200m or 500m coil is the right buy. If you have not worked out your total pipe yet, start with how much underfloor heating pipe you need.

How long can one UFH loop be?

About 100m for 16mm pipe and 80m for 12mm pipe, including the tails to and from the manifold. One manufacturer gives a 100m maximum circuit length for its screeded systems, designed at a 50°C flow temperature, and 80m for 12mm pipe in its overlay systems. Longer loops need more pump pressure to push water round and are harder to balance.

That loop limit is what drives the coil choice. A 16mm loop of 100m with 10m of tails leaves 90m in the floor, which covers about 13.5m² at 150mm centres. Larger rooms are split into two or more loops of similar length. Our guide to loop lengths and loops per room explains how to split them.

Why does each loop need to be one length of pipe?

Because a joint buried in screed or under boards is a joint you can never reach again. We recommend every loop runs as one continuous length from the flow port, round the room and back to the return port, with no couplings in the floor. Keep joints for repairs, not for using up offcuts.

So when you order, the question is not "how many metres do I need?" It is "can I cut every loop I need, whole, from the coils I buy?" A 500m coil can give five 100m loops. Five 100m coils can too. Five 120m offcuts left over from other jobs can give five loops as well, but two 50m offcuts cannot give one.

Which coil sizes can I buy?

These are the coil lengths we stock for each UFH pipe. Most homes use 16mm pipe in screed, castellated panels or routed boards, and 12mm pipe in low-profile overlay panels. Our guide to UFH pipe types compared helps you choose between them.

Pipe	Size	Coil lengths
3-layer PERT-EVOH	16 x 2.0mm	100m, 200m, 240m, 400m, 500m
3-layer PERT-EVOH	12 x 2.0mm	80m, 320m
3-layer PERT-EVOH	10 x 1.3mm	80m, 240m
3-layer PERT-EVOH	20 x 2.0mm	300m
5-layer PERT-EVOH	16 x 2.0mm	200m, 400m
PERT-AL-PERT multilayer	16mm	50m, 80m, 100m, 150m, 200m, 300m, 500m
PERT-AL-PERT multilayer	15mm	100m
PERT-AL-PERT multilayer	12mm	80m, 160m, 240m

The product pages show the current price for each pipe and coil length.

How do I turn loop lengths into a coil order?

List every loop with its full length, then fit them into coils like packing boxes, longest first. Here is the method:

1. Work out the pipe in each room. Heated floor area times pipe per m²: about 10m at 100mm centres, 6.7m at 150mm and 5m at 200mm.
2. Split into loops. Keep each 16mm loop to about 100m including tails, and 12mm loops to about 80m.
3. Add the tails. Measure from the manifold to the room and back for each loop.
4. Add an allowance. We add 10% plus 1m to each loop for cutting, bends and connecting at the manifold.
5. Pack the loops into coils. Start with the longest loop, add the next that fits, and move to a new coil when the next loop will not fit in what is left.
6. Compare the options. Try one long coil, then a mix of shorter coils, and see which leaves the smallest offcut.

Pipe per m² figures vary a little by maker. One manufacturer, for example, quotes about 9m per m² at 100mm and 4.5m per m² at 200mm for its systems. Use the figure for the floor system you are laying, and round up. Our guide to underfloor heating pipe centres explains how spacing is chosen.

What does a worked example look like?

Take a ground floor in 16mm pipe at 150mm centres with six loops, each already worked out with tails and allowance:

Loop	Length
Lounge loop 1	95m
Lounge loop 2	95m
Kitchen	90m
Dining	80m
Hall	55m
Cloakroom	30m
Total	445m

Now try three ways of buying it:

Order	How the loops fit	Left over
1 x 500m	All six loops, one after another	55m
1 x 400m + 1 x 100m	400m: both lounge, kitchen, dining (360m). 100m: hall and cloakroom (85m)	40m + 15m
3 x 200m	Both lounge (190m), kitchen and dining (170m), hall and cloakroom (85m)	10m + 30m + 115m

The first two use the same 500m of pipe and leave 55m spare. The three 200m coils buy 100m more pipe for the same job. One long coil is also quicker to lay, because you only set up the pipe decoiler once.

For a 12mm overlay floor, the same logic works with 80m loops. A 320m coil of 12mm PERT-EVOH gives four 80m loops, while 80m coils suit a single small room such as an en-suite.

Should I buy a 100m, 200m or 500m coil?

Choose by the number of loops, not by the total metres. As a guide:

Coil	Best for	Watch out for
100m	One loop: a single room up to about 13m² at 150mm, or a small extension	A loop over 100m will not fit
200m or 240m	Two loops: a large room or two rooms on one manifold	Several 200m coils can leave awkward offcuts
400m	Four loops, or a floor of three to four rooms	Plan the loop order before you cut
500m	A whole floor or a house: five loops or more	Use a decoiler; it is a lot of pipe to handle by hand

If your loops are all close to 100m, coils that are exact multiples of 100m work best. If you have a mix of long and short loops, a single long coil gives you the most freedom to fit them in.

What mistakes should I avoid when ordering pipe coils?

• Ordering by total metres alone. The six loops in the example total 445m, but they do not fit into four 100m coils plus a 50m coil, because the 55m hall loop will not fit in any of the pieces left over.
• Forgetting the tails. A room at the far end of the house can need 20m or more of tails per loop. Measure them.
• Buying two pipe types for one manifold. Each pipe size needs its own matching Eurocone connector cores, two per loop. Keep one pipe size per manifold where you can.
• Laying loops in the wrong order. If you cut the short loops from a long coil first, you may not have a long enough piece left for the biggest room. Lay the longest loops first.
• Planning to join offcuts. Keep loops whole. Spare pipe is useful for repairs and for primary runs, not for splicing loops.

Frequently asked questions

How many rooms does a 500m coil of UFH pipe cover?

It depends on room size and tails, but a 500m coil of 16mm pipe gives about five loops of up to 100m. At 150mm centres, that is roughly 60 to 70m² of floor, spread across as many rooms as those loops serve.

How much floor does a 100m coil of UFH pipe cover?

At 150mm centres, about 6.7m of pipe goes into each m². After 10m of tails, a 100m coil covers about 13.5m² as one loop. At 100mm centres it covers less, about 9m².

Can I join two pieces of UFH pipe to make one loop?

We do not recommend it. A joint in the floor cannot be reached once the screed or boards are down. Plan your coils so each loop is one length, and keep joints for repairs.

Is it cheaper to buy one big coil or several small ones?

Compare the coil prices on the product page for your job. As the worked example shows, the bigger saving usually comes from wasting less pipe, and one long coil often leaves the smallest offcut.

What coil size do I need for one room?

For a single room up to about 13m² in 16mm pipe at 150mm centres, a 100m coil gives one loop. For a larger room that needs two loops, choose a 200m or 240m coil.

What size coil for 12mm overlay pipe?

Plan 12mm loops at up to 80m. An 80m coil gives one loop for a small room, and a 320m coil of 12mm PERT-EVOH gives four loops.

Should I order spare pipe?

The 10% plus 1m allowance on each loop covers cutting and bends. A small offcut left on the coil is useful to keep for future repairs.