Wet Underfloor Heating: A Plumber's Guide to UFH Pipe Fittings, Pump Assemblies, and Installation Components

Wet underfloor heating distributes low-temperature hot water through a network of loops embedded in or laid on a floor structure, heating the room from below. It is increasingly standard in new builds and high-specification refurbishments — and increasingly expected by clients having a bathroom or kitchen retiled. This guide covers the wet UFH components stocked at APM: Henco press-fit fittings for 16mm and 26mm pipe, the Emmeti pump assembly, and Novatherm tile backer board.

How a Wet UFH System Works

A wet UFH system consists of four main elements:

1. The pipe loops — typically 16mm multilayer composite (MLCP) or barrier pipe, laid in a continuous loop per room or zone at 150–200mm centres.
2. The manifold — a flow and return header that feeds each loop independently, with individual balancing valves and actuators per zone.
3. The pump and mixing assembly — circulates water around the loops and blends the boiler flow temperature down to the 35–45°C required for UFH (vs 65–70°C for radiators).
4. The floor build-up — either a screed pour (wet system), a dry system over battens, or a thin system using heat-spreading plates under tiles. Each requires appropriate insulation below the heating layer.

Henco Press-Fit Pipe Fittings — 16mm

Henco is a Belgian manufacturer of multilayer composite pipe and press-fit fittings specifically designed for underfloor heating and plumbing. The 16mm range covers manifold connections, loop-to-primary transitions, and repair joints — the fittings you need when connecting or repairing a UFH loop.

16mm Straight Adaptors

• Henco 16mm × ½" Straight Female Iron Adaptor — 16mm press-fit to ½" BSP female. For connecting the UFH loop pipe to a manifold port (most manifolds have ½" BSP outlets).
• Henco 16mm × ½" Straight Male Iron Adaptor — 16mm press-fit to ½" BSP male.
• Henco 16mm × 15mm Press-Fit Adaptor to Copper Compression — for transitions between 16mm Henco MLCP and 15mm copper supply pipe. Common at the point where a UFH loop connects to a conventional copper plumbing run.

16mm Elbows and Bends

• Henco 16mm × ½" 90° Bend — Male Iron
• Henco 16mm × ½" 90° Bend — Female Iron
• Henco 16mm × ⅜" 90° Bend — Female Iron
• Henco 16mm × 15mm Press-Fit Elbow to Copper Compression
• Henco 16mm × 16mm Compression Elbow 90°

16mm Tees

• Henco 16mm × 16mm × 16mm Press-Fit T-Piece — equal tee for branching 16mm loop pipe.
• Henco 16mm × ½" × 16mm T-Piece Female Iron Centre — T with a ½" BSP centre outlet. For adding a manifold branch mid-loop or connecting a temperature sensor port.

16mm Backplate Elbow

• Henco 16mm × ½" Backplate Elbow Female — surface-fixing elbow for terminating a UFH loop at a wall-mounted manifold port, with integral backplate for screw fixing.

16mm Repair Coupling

• Henco 16mm × 16mm Repair Coupling — for repairing a damaged or accidentally cut UFH loop without disturbing the screed. The repair coupling slides over the pipe and locks without requiring access to the pipe end. Essential for any UFH remediation job.

Henco Press-Fit Fittings — 26mm (Primary Circuit)

26mm Henco pipe and fittings are used for the primary supply and return pipework connecting the boiler to the UFH manifold — the same function that 22mm copper serves in a conventional heating system, but in MLCP for lower heat loss and easier routing.

26mm Straight and Couplings

• Henco 26mm × 26mm Straight Coupling
• Henco 26mm × 22mm Straight Coupling to Copper — press-fit 26mm to 22mm copper compression. For transitioning from MLCP primary pipe to a copper boiler connection or existing copper distribution circuit.
• Henco 26mm × 16mm Reducing Coupling — steps down from 26mm primary to 16mm loop pipe at the manifold input.

26mm Elbows

• Henco 26mm × 26mm Elbow 90°

26mm Iron Adaptors

• Henco 26mm × 1" Straight Female Iron — for connecting 26mm MLCP to 1" BSP manifold inlets or large valves.
• Henco 26mm × 1" Straight Male Iron
• Henco 26mm × 1" Straight Female Iron Adaptor
• Henco 26mm × ½" Straight Male
• Henco 26mm × ¾" Straight Female Iron Adaptor
• Henco 26mm × ¾" Straight Male Iron Adaptor
• Henco 26mm × ¾" Bend 90° Female Iron
• Henco 26mm × ¾" Bend 90° Male Iron

26mm Tees

• Henco 26mm × 26mm × 26mm T-Piece
• Henco 26mm × 16mm × 16mm T-Centre and Line Reducer — 26mm primary run with two 16mm branch outlets. For connecting dual loop branches off a single primary pipe without a manifold.
• Henco 26mm × 16mm × 26mm T-Reducer Iron Centre
• Henco 26mm × ¾" × 26mm T-Female Iron Centre

26mm Repair Coupling

• Henco 26mm × 26mm Repair Coupling

Emmeti UFH Pump Assembly

The pump assembly is the heart of a wet UFH system — it circulates water around the loops and blends the boiler flow temperature down to the correct UFH supply temperature. The Emmeti assembly combines three components in a pre-assembled unit:

• WILO circulation pump — moves water around the UFH loops. Wilo is one of the leading pump manufacturers for heating applications in the UK.
• Thermostatic mixing valve (TMV) — blends hot boiler flow with cooler return water to deliver UFH supply temperature, typically 35–45°C. Without this, UFH fed directly from a combi or system boiler at 65–70°C would overheat the floor and create comfort problems.
• T3 3-way valve — provides zone control, allowing the UFH to be isolated or blended independently of the rest of the heating system.

• Emmeti UFH Pump Assembly T3 3W TMV with WILO Pump

This is a pre-assembled unit — the pump and TMV arrive already configured and ready to connect between the boiler primary circuit and the manifold. It significantly reduces installation time compared to assembling components separately.

Novatherm Tile Backer Board

Novatherm is a rigid thermal insulation board used as a tile backer in wet room and tiled floor applications, including directly over wet UFH screed. Its purpose in a UFH installation is twofold:

1. Thermal break: Prevents heat generated by the UFH system conducting downward into the subfloor structure rather than upward into the room. Without adequate floor insulation, a significant proportion of UFH heat is lost downward — particularly in ground-floor installations over an uninsulated slab.
2. Tile decoupling: Provides a stable, low-movement substrate for floor tiles. UFH systems cycle between heating and resting — the thermal movement of a screed floor can crack tiles laid directly on a rigid subfloor without a decoupling layer.

• Novatherm Tile Backer Board 1200 × 600mm × 6mm — 6mm thickness provides both the thermal break and decoupling function for typical domestic tile-over-screed applications. Each sheet covers 0.72m². For a standard kitchen or bathroom, calculate floor area ÷ 0.72 to determine sheet quantity, plus 10% waste allowance for cuts.

Installation Notes

UFH supply temperature

BS EN 1264 sets the maximum UFH floor surface temperature at 29°C for occupied areas (9°C above normal room temperature). This translates to a supply water temperature of approximately 35–45°C depending on the floor covering — lower for thick carpet or timber, higher for tile or stone. The Emmeti TMV assembly is set to maintain this blend automatically.

Pipe spacing

Standard loop spacing for domestic UFH is 150–200mm centres for a screed system and 100–150mm for a low-profile dry system. Closer spacing increases heat output but requires more pipe per m². 16mm pipe at 150mm centres in a standard screed delivers approximately 60–80W/m² at 40°C flow temperature — sufficient for well-insulated modern construction.

Commissioning

UFH systems must be filled, pressure tested, and flushed before the manifold actuators are fitted and the controls are commissioned. Pressure test at 6 bar for 30 minutes with no drop before pouring screed or closing the floor. Do not operate the system at full boiler temperature during the first 28 days — most screeds require a gradual temperature rise to cure properly and prevent cracking.

Quick Reference

All UFH components are in stock for same-day collection at our Acton trade counter. Fitting out a development or commercial UFH installation? Call ahead to check quantities.

APM Plumbing & Electrical | 24 Western Avenue, Acton, London W3 7TZ | 020 8702 8080 | apmi.uk