The Manthorpe GRS seals the gap where radiator pipes pass through walls, preventing heat loss and air leakage. Designed for plastic pipework, it guides pipes cleanly, eliminates kinks, and helps meet Part L air pressure test requirements. Simple to fit, effective from day one.
The Manthorpe GRS Radiator Pipe Guide and Seal addresses one of those gaps in the building process that everyone quietly ignores until a pressure test fails. Where radiator pipes pass through a wall, there is almost always an unsealed gap. Air moves freely through it, heat disappears, and the householder ends up wondering why their bills are higher than expected. The GRS fits at that junction and closes it off with an airtight TPE gasket, giving you a clean, compliant finish that holds up to scrutiny.
It is designed specifically for plastic pipework, which has become the standard choice on most domestic heating installs. The 80mm radius pipe guide does the practical work of bringing the pipe round to the radiator without kinking or sagging, both of which cause longer-term problems behind plasterboard or skim. The built-in skim bead gives the plasterer a clean line to work up to, so there is no guesswork about where to finish. Four fixing points hold the whole assembly firmly in place, and the clamps grip the pipework to stop it moving or chafing against the wall edge over time.
How the Manthorpe GRS Helps with Part L Compliance
Part L of the Building Regulations now requires air pressure testing on new builds and major refurbishments. Radiator pipe penetrations are one of the common failure points, and one that is easy to overlook when you are focused on loft hatches and window seals. The Manthorpe GRS deals with it at the point of installation rather than as a remedial fix after the test. At under a fiver, it is one of the more cost-effective ways to tick a compliance box. Fit it during first fix, plaster up to the bead, and the job is done properly first time.
Pro Tip: Fit the GRS before the plasterer comes in so the skim bead gets buried cleanly into the finish coat — trying to add it afterwards means cutting back and making a mess of a wall that has already been skimmed.
The Manthorpe GRS is used on new build and refurbishment projects wherever plastic radiator pipes pass through an external or internal wall. It is a standard fit on domestic heating installations where Part L air leakage testing is required, and it is equally useful on commercial properties undergoing SAP assessments or energy performance upgrades. Heating engineers, plumbers and first-fix joiners all encounter this situation regularly. The GRS handles it neatly, regardless of whether the wall is blockwork, timber frame or dry-lined.
Best For
New build heating installations
Refurbishment projects requiring Part L compliance
Plastic radiator pipework penetrations
Air pressure testing preparation
Domestic and light commercial heating systems
Works With
Plastic radiator pipes
Blockwork walls
Timber frame construction
Dry-lined walls
Standard plaster skim finish
Key Features
Airtight twin-shot TPE gasket
80mm radius pipe guide prevents kinks and sag
Integrated skim bead for clean plaster finish
Four fixing points for accurate positioning
Clamps hold pipework securely against chafing
Supports Part L air leakage compliance
Not suitable for: Not designed for copper pipework or pipes with larger diameters than the guide accommodates. Not suitable as a fire-stopping solution where pipes penetrate fire-rated compartment walls.
Fit the GRS at first-fix stage, before plastering begins. Position it at the wall penetration point, feed the plastic pipe through the guide, and secure it with the four fixing points. The clamps hold the pipe in place and stop it shifting during the rest of the build. Once fixed, the skim bead sits proud of the wall surface, giving the plasterer a clear stopping edge.
Make sure the gasket seats flush against the wall face to maintain the airtight seal. Any gap here will compromise the barrier and potentially show up during the pressure test. Once the skim coat is applied and dried, the installation is complete and no further action is required.
Mark the pipe penetration position on the wall before cutting
Core or cut the wall opening to the correct diameter for the plastic pipe
Feed the plastic pipe through the 80mm radius guide section of the GRS
Position the unit flush against the wall face, ensuring the TPE gasket seats properly
Fix securely using all four fixing points
Tighten the clamps to hold the pipework firmly without over-compressing the pipe
Plaster up to the integrated skim bead for a clean, finished edge
Check the gasket seal is fully intact before the pressure test is carried out
Does the Manthorpe GRS work with copper pipes as well as plastic?
It is designed for plastic radiator pipes, which are now the most common choice on new installations. Copper pipe has a different rigidity and the guide geometry is optimised for plastic. Using it with copper is not recommended.
Will the GRS help pass a Part L air pressure test?
Yes, that is one of its main purposes. The airtight TPE gasket seals the gap around the pipe at the wall face, which is a known air leakage point. Fitting it correctly at first-fix stage means this penetration will not be a weak spot when the test is carried out.
At what stage of the build should the GRS be installed?
First fix, before plastering. The integrated skim bead is designed to be built into the plaster coat, so the plasterer finishes up to it. Trying to fit it after skimming means cutting back and re-finishing the wall.
The Manthorpe GRS is manufactured with a twin-shot TPE (thermoplastic elastomer) gasket, which provides the airtight seal at the wall face. TPE offers good flexibility and compression recovery, maintaining the seal over time without cracking or shrinking. The pipe guide section is formed at an 80mm radius, sufficient to redirect plastic pipework without introducing stress or kinking. The body and skim bead are rigid plastic construction, compatible with standard plaster skim finishes.
Manufacturer
Manthorpe Building Products
SKU
GRS
Pipe Type Compatibility
Plastic radiator pipes
Pipe Guide Radius
80mm
Gasket Material
Twin-shot TPE (thermoplastic elastomer)
Fixing Points
4
Regulation Compliance
Supports Part L air leakage requirements
Finish
Integrated skim bead for plastering
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