JG Speedfit and Hep2O Plastic Push-Fit Systems — A Trade Guide

What Are Plastic Push-Fit Plumbing Systems?

Plastic push-fit plumbing systems — principally JG Speedfit (polybutylene, PB) and Hep2O (cross-linked polyethylene, PEX) — are designed for concealed domestic hot and cold water pipework in new build and refurbishment. They connect without tools, flux, or heat, and are approved for use under building regulations where properly installed with support and expansion allowance.

Both systems are WRAS-approved for potable water and carry British Board of Agrément (BBA) certificates. They are not interchangeable — JG Speedfit and Hep2O use different O-ring dimensions, and fittings must never be mixed.

For a deeper dive into each brand, see our dedicated guides: JG Speedfit Push-Fit Plumbing: The Complete Guide and Hep2O Push-Fit Plumbing: The Complete Guide. For a wider comparison of joining methods, see Compression, Push-Fit, and End Feed Fittings: Which to Use and When.

JG Speedfit (Polybutylene)

Pipe Properties

JG Speedfit pipe is manufactured from polybutylene (PB) to BS 7291-3. It is flexible, cream-coloured, and available in 10mm, 15mm, 22mm, and 28mm OD. Maximum working pressure: 10 bar at 20°C, 4 bar at 82°C. Maximum working temperature: 82°C continuous, 95°C short-term.

Key characteristics:

• High flexibility — tight radius bends (minimum bend radius = 8 × OD) without a bending spring
• Excellent impact resistance at low temperature — suitable for external or unheated spaces
• Creep (long-term deformation under load) is higher than copper; all clips and hangers must be at the specified centres
• Susceptible to UV degradation — must not be exposed to sunlight in service

Fittings

JG Speedfit fittings use a collet-and-O-ring mechanism. The collet grips the pipe's OD; the O-ring forms the seal. Key points:

• The pipe must be cut square — use a pipe slice or tube cutter, never a hacksaw
• Deburr and ream the cut end to prevent O-ring damage
• Insert the stiffener insert into the pipe end before fitting — this is mandatory on all JG Speedfit pipe connections. Without the insert, the pipe can collapse inside the fitting under pressure and O-ring sealing is compromised
• Push the pipe fully home until it bottoms out (feel the resistance change)
• Demount tool required to release — do not attempt to pull fittings apart without the demounting tool

Krobahn Pipe Slice 15mm

£10.99

Barrier Pipe vs Standard Pipe

Where JG Speedfit connects to a sealed central heating circuit (including underfloor heating), barrier pipe is required. Standard JG Speedfit polybutylene is oxygen-permeable; in closed circuits, oxygen ingress causes accelerated corrosion of ferrous components (boilers, radiators, pumps).

Barrier pipe has an EVOH (ethylene vinyl alcohol) layer that limits oxygen permeability to less than 0.1 g/m³/day (as per DIN 4726). It is typically identified by the red or blue stripe in addition to the standard cream colour. Always specify barrier pipe for underfloor heating manifolds and closed-circuit primary pipework. See our Wet Underfloor Heating Installation Guide for manifold and barrier pipe requirements in screed systems.

Hep2O (Cross-Linked Polyethylene, PEX)

Pipe Properties

Hep2O pipe is manufactured from cross-linked polyethylene (PEX-b) to BS 7291-2. It is more rigid than JG Speedfit, white or grey in colour, and available in 10mm, 15mm, 22mm, and 28mm OD. Maximum working pressure: 10 bar at 20°C. Maximum working temperature: 95°C continuous.

PEX has lower creep than polybutylene and recovers its shape after bending — it does not permanently deform. This makes it suitable for tighter, more controlled pipe runs in partition walls and joisted floors.

Fittings

Hep2O fittings use a demountable push-fit mechanism with a stainless steel grab ring and EPDM O-ring. The same prep rules apply: cut square, deburr, and fit the stiffener insert. Hep2O also supply a superseal fitting range for concealed connections — these are designed for embed in screed or plasterboard and are not demountable after installation (permanent connection).

Barrier Pipe for Heating

As with JG Speedfit, standard PEX pipe is oxygen-permeable. Hep2O Barrier pipe incorporates an EVOH layer and is required for all closed heating circuits. It is identifiable by a specific colour code (typically blue-striped for cold, red-striped for hot/heating).

Key Installation Requirements

Pipe Support Centres

Both systems require more frequent clipping than copper. Failure to clip at the correct centres leads to sagging, stress at fittings, and long-term leak risk. See our guide to Pipe Clips and Fixings: Spacing, Types, and Correct Specification for full detail on clip selection and fixing methods.

Embrass Peerless 15mm Talon Plastic Pipe Clip Single Hinged — Pack of 50

£6.99

Talon Nail In Pipe Clip 22mm

£0.20

Thermal Expansion Allowance

Plastic pipe expands significantly with temperature change. Linear expansion coefficient: PB approximately 0.13 mm/m/°C; PEX approximately 0.15 mm/m/°C — roughly 10 times that of copper. A 10 metre run of 15mm pipe on a hot water circuit (ΔT = 55°C) will expand by approximately 72mm.

Expansion must be accommodated with:

• Directional changes in pipework routing (natural offsets)
• Expansion loops where long straight runs cannot be avoided
• Proper use of fixed points (anchor brackets) and guide brackets to direct expansion into loops

Never box in a long straight run of plastic pipe without expansion provision — the fitting stress created can cause joint failure.

Cold Water — UV Protection

Both systems must be protected from UV light. Where pipe runs are exposed (e.g., along an external wall before boxing), either sheath in foam insulation (which also provides UV protection) or use UV-resistant pipe lagging. For a full guide to materials, thickness, and application, see Pipe Lagging and Insulation: A Practical Guide for Plumbers.

Tubolit 15mm × 9mm × 1m Pipe Insulation Lagging

£0.97

Tubolit 22mm × 9mm × 1m Pipe Insulation Lagging

£0.99

Minimum Cover and Frost Protection

For pipes in external or unheated locations, insulate to prevent freezing. JG Speedfit's flexibility makes it more tolerant of freeze-thaw cycles than copper but it is not freeze-proof. Minimum recommended insulation: 25mm wall thickness for pipes in roof spaces or external ducts.

Transition to Copper and Other Systems

Both systems offer dedicated transition fittings: push-fit to compression, push-fit to copper solder, and push-fit to BSP threaded. When connecting to copper compression fittings, fit the correct insert and ensure the olive is sized for the OD of the plastic pipe (same as copper OD). Polybutylene is softer than copper — do not overtighten compression fittings; hand-tight plus 1.5 turns is sufficient.

For full detail on compression fitting assembly, torque, and olive selection, see our Compression Fittings: A Trade Guide to DZR Brass, Olives, and Sizing. For copper-based alternatives, see Copper Press-Fit Fittings: Geberit Mapress, Conex Banninger M-Press, and Viega Propress Guide.

Common Installation Mistakes

Omitting the Stiffener Insert

The most frequent cause of push-fit leaks. The insert supports the pipe wall inside the fitting. Without it, the O-ring cuts into the pipe under pressure. Carry an ample supply of inserts — they are inexpensive and mandatory.

Mixing Speedfit and Hep2O Fittings

The two systems use nominally the same pipe OD but different O-ring and collet geometry. Cross-fitting will appear to engage but will leak under pressure. Keep the two systems visually segregated on site and label pipes if both are used in the same building.

Using Standard Pipe on Heating Circuits

Standard (non-barrier) pipe on closed circuits will allow oxygen ingress. Oxygen causes magnetite sludge formation and pin-hole corrosion in boilers and heat exchangers. If a warranty claim arises, the manufacturer will check whether barrier pipe was used — non-compliance voids coverage.

Insufficient Expansion Allowance

Particularly in newly commissioned systems, long hot water pipe runs will bow and creak if expansion is not addressed. In worst cases, strain at terminal fittings can cause joint release. Add an expansion loop every 5–8 metres on straight hot water runs.

Pipe Not Fully Inserted

A partially inserted push-fit connection may hold pressure during commissioning but fail under thermal cycling. Always verify full insertion — mark the pipe 25mm from the end before pushing; the mark should be at the fitting face once pushed home.

Pressure Testing

Plastic push-fit systems must be hydraulic pressure-tested before concealment. BS EN 806 recommends a test pressure of 1.5 times the maximum working pressure (for domestic, 10 bar system: test at 15 bar). In practice, most building regulations and NHBC standards require:

• Visual inspection of all fittings before test
• Raise to test pressure over 30 minutes
• Hold for 30 minutes minimum — no visible drop beyond the first 30 minutes (first 30 minutes allowed for pipe stabilisation)
• Record results in the building logbook

See our full guide: Pressure Testing Plumbing and Heating Pipework: Procedures, Standards, and Equipment.

System Selection: When to Choose Plastic Push-Fit

Key Standards and Approvals

• BS 7291-2 — PEX (cross-linked polyethylene) pipe for hot and cold water
• BS 7291-3 — polybutylene pipe for hot and cold water
• BS EN 12828 — heating systems in buildings (relevant to barrier pipe requirements)
• DIN 4726 — maximum oxygen permeability for barrier pipe in heating systems
• WRAS approval — required for all potable water contact products
• BBA certificate — both JG Speedfit and Hep2O carry current certificates
• BS EN 806 / BS 8558 — design and installation of water supply installations in buildings