Flexi pipes for taps, toilets and cables: what each one is

What a flexi pipe is

Ask for a flexi pipe in a hardware shop and you may be handed one of two products. The plumber’s flexi pipe is a short flexible hose, usually covered in a stainless steel braid, that runs from the water supply pipe to a tap, a basin mixer, a sink or a toilet cistern. The electrician’s flexi pipe is a flexible conduit, a ribbed tube that carries cables where a rigid conduit cannot bend.

Neither is a garden or washing hose; those are covered on the hose pipe page. Before buying, say which job the flexi pipe is for, and take the thread or pipe size of both ends.

Braided flexi pipes for taps and toilets

A tap connector has three parts: a rubber inner hose that carries the water, a stainless steel braid that holds it under pressure, and metal or plastic fittings crimped onto each end. The Hydraflex tap flexibles data sheet gives a typical build:

Braided flexi pipes for taps and toilets

Part	Hydraflex tap flexible
Inner hose	EPDM rubber, 10 mm bore
Braid	304 stainless steel
Metal fittings	brass, CW617N and CW614N
Lengths	300, 500 and 900 mm
Ends	15 mm compression
Uses named	sinks, basins and toilets, domestic and commercial washrooms

Hydraflex describes these flexi pipes as a way to bridge pipework that does not line up with the appliance, which is the usual reason to use one: when the supply pipe does not meet the tap tail or cistern inlet squarely, the hose takes up the difference. The firm also notes that the range is not suitable as fan coil hose for air-conditioning units. The taps page covers the tap end of the connection, and the toilets page the cistern types a connector feeds.

Brass or plastic ends: pressure and temperature

The end fittings set the limits. Hydraflex rates the same braided flexi pipe at 15 bar and 70°C with brass fittings, but at 10 bar and 65°C with John Guest push-fit and plastic fittings made of polyacetal with an EPDM O-ring. With plastic ends, the pressure rating is a third lower (our calculation: 1 − 10 ÷ 15).

For the hot side of a mixer or a water heater, check the temperature figure first: neither version in this data sheet is rated above 70°C. Hot water systems that run hotter need a connector whose data sheet states a higher temperature.

Flexible conduit for cables

The electrical flexi pipe protects wiring, not water. Electro Persian Sepahan, an Iranian maker, describes four kinds of metal flexible conduit:

• Coated: a spiral metal strip covered in PVC, which resists light, heat, UV, moisture and chemicals; used in open and wet places and for cables run underground.
• Uncoated: the bare metal spiral, with less protection from outside damage.
• Shielded: metal screening against magnetic interference, for communication wiring indoors.
• Shielded and coated: the same with a plastic outer layer, for communication wiring outdoors.

The fittings matter as much as the flexi pipe itself. The same maker warns that simple single- and double-screw glands hold weakly, can pull apart when the conduit is stretched and do not keep out dirt or moisture, while sealed conduit connectors with washers do. Male connectors join the conduit to a junction box or cable tray, female ones to steel conduit, and a coupler joins two lengths.

What to check when you buy

• Job. Water connector or cable conduit: they are not interchangeable.
• Ends. For water, the thread or compression size at the tap or cistern and at the supply pipe; Hydraflex uses 15 mm compression on both ends of this range.
• Length. Long enough to bridge the gap; 300, 500 and 900 mm are common stock lengths in the Hydraflex range.
• Rating. Pressure and temperature on the data sheet, especially for hot water.
• Materials. EPDM liner, stainless braid and brass ends for water; PVC-coated conduit and sealed connectors for cables in wet places.