Colglo Blog

Choosing and Using Polyplumb Underfloor Heating Pipe

Posted by Collister & Glover on Aug 22, 2018 11:28:29 AM
Collister & Glover

Underfloor Heating Pipe. Which do I choose? Grey Heating and Plumbing Pipe, Metal Composite Pipe or Flexible Under fFoor Heating Pipe? Lots of options are available but what are the benefits?|PLUS | Cutting and adding fittings to the common 12mm and 18mm

Selecting the right pipe

Polypipe offer three different types of pipe for use in their underfloor heating systems. Sizes range from 12 mm to 18 mm in diameter.

Grey Plumbing and Heating Pipe

Polybutylene BS 7291 Class S. Manufactured to the highest standards, this pipe is suitable for use in both underfloor heating and radiator central heating systems.

It has an oxygen diffusion barrier that prevents oxygen entering the system. Also, any remaining coil lengths or off cuts can be used to install any domestic hot and cold water services. Which can help to save money on the overall installation

Ultra-Flexible Underfloor Heating Pipe

BS EN15876. Designed specifically for use in underfloor heating systems only, this polybutylene barrier pipe is ultra-flexible making it easy to bend and form.  In some installations ease of handling is essential e.g. when installing solid floor pipe staple systems from below.

Metal Composite Pipe (MCP)

BS EN21003. MCP  is mainly used for rail and staple solid floor type installation as it is very easy to shape. pipe, it is made from raised temperature polyethylene (PE-RT) and utilises an aluminium inner barrier layer. This pipe was designed to be used in underfloor heating systems only. 

The Pipe Usage Chart below shows which pipe type can be used with each system and its connection type.


Cutting and Preparing Underfloor Heating Pipe

Connections on MCP
The 16mm metal composite pipe is connected to the underfloor heating manifold by the use of 16mm Eurocone adaptors.


In order to make the joint correctly the following procedure should be used.

Step 1: Cutting the Polyplumb pipe


Check the pipe is not scored or scratched in any way and if it is, cut back to a point where there is no damage. Using a Polypipe pipe cutter, cut the pipe squarely using the “K” marks on the pipe as a guide. These marks indicate when the pipe has been inserted into the fitting correctly. 

Wherever possible, use a rotational pipe cutter when cutting pipe. Ensure that all cut ends have a rounded lead in, with copper pipe ensure all burrs removed. Never use a hacksaw to cut the pipe, as the two ends of the pipe should meet flush. (You will need to mark the insertion depth for pipe stiffeners as 4. and 5. below)

Step 2: If Required: De-bur the inner wall of the pipe. Insert a pipe stiffener


Insert a pipe stiffener into the pipe (not required on copper)

Pipe stiffeners are an integral part of the joint when using Polypipe grey pipe with either PolyPlumb fittings or compression fittings and need to be fully inserted into the pipe end.

There are 3 different types of pipe stiffeners dependant on fitting type or installer preference:

  • Plastic pipe stiffeners can be used with all pushfit ranges – PolyPlumb, PolyFit and PolyMax.
  • Stainless steel stiffeners can also be used with all push-fit ranges – PolyPlumb, PolyFit and PolyMax.
  • Sealed pipe stiffeners, which provide enhanced sealing can be used with PolyFit and PolyMax only.


Step 3: Visually check fitting and fitting components


Visually check that all components are present, undamaged and free from contamination.

Lubricants:  All Polypipe fittings are supplied with pre-lubricated EPDM ‘O’ rings. If any further lubrication is required only Polypipe silicone lubricant should be used. Do not use other substances such as solder flux as this will deteriorate the joint.

Step 4: Insert the fitting or eurocone fully into the pipe


Insert pipe into the fitting, ensuring it is inserted to the full socket depth. There is a depth make on the pipe denoted by a “K” .

Step 5: Checking the joint security


Slight pulls on the pipe will confirm that the pipe is inserted past the grab ring and that a grab ring was present in the fitting. It does not ensure that the pipe is fully inserted as this you can only confirmed this by using the depth insertion mark.

IMPORTANT NOTE: Do not re-joint

Pipe should never be removed from a jointed PolyPlumb fitting.  If the same fitting is then re-jointed, there is real risk that the outer edge of the grab ring will have become damaged and this will reduce the pull-out performance of the joint when subjected to pressure. The joint will almost certainly fail prematurely.


Topics: underfloor heating