Flexible Tap Connectors — 15mm, 22mm, Monobloc Tap Tails, and Washers for UK Plumbers

Flexible tap connectors are used on almost every domestic tap installation — kitchen sinks, basin taps, bath taps, bidets, and utility room taps all need a flexible connection between the rigid supply pipe and the tap tail. Knowing which connector size, thread, and length to select saves van time on the day. This guide covers the common types, how to size them correctly, and when a built-in isolating valve is worth fitting.

Why Use a Flexible Tap Connector?

Rigid copper connections to tap tails crack under vibration, thermal movement, and minor misalignment. A braided flexible connector — typically 300 to 500 mm of corrugated stainless steel with a braided outer sleeve — absorbs all of this while making it easy to align the supply pipe without bending or soldering under a sink.

Flexible connectors are also the right choice when a tap has to come off for servicing. With an isolating valve either on the connector or on the supply run, the tap can be swapped out without isolating the zone or draining down.

How to Size a Flexible Tap Connector

Flexible tap connectors have two different connections — one for the supply pipe and one for the tap tail. You need to match both ends:

• Supply pipe end: 15 mm (standard domestic) or 22 mm (bath taps on larger bore supplies). Some connectors use a 1/2" push-fit end instead of a compression fitting.
• Tap tail end: Most kitchen and bathroom basin taps have a 1/2" BSP male tail. Bath taps typically have a 3/4" BSP male tail. Monobloc kitchen taps (single-hole mixers) use M10 or M12 machine thread tap tails — these need a different connector entirely.
• Length: 300 mm covers most under-sink situations. Measure the gap between the supply pipe valve and the tap tail before ordering — 150 mm is tight but usable in shallow cupboards; 500 mm and 900 mm extensions suit awkward or deep-set taps.

Standard Flexible Tap Connectors (1/2" and 3/4" BSP)

The most common connector in UK domestic plumbing is 15 mm compression × 1/2" BSP × 300 mm — this connects a standard 15 mm copper supply to a standard kitchen or basin tap. For bath taps, 15 mm × 3/4" BSP × 300 mm or 22 mm × 3/4" BSP × 300 mm are the correct sizes depending on your supply bore.

When fitting a standard connector, wrap the 1/2" BSP male tail thread with two to three turns of PTFE and use the supplied fibre or rubber washer in the nut at the compression end. Overtightening the tap tail connection will split the olive or crack the fitting body — hand-tight plus a quarter turn with a spanner is enough.

Connectors with Built-In Isolating Valves

For new installations and bathroom refurbs, fitting a connector with an integral quarter-turn isolating valve is best practice. It removes the need for a separate mini-stop on the supply pipe and gives whoever services the tap a clean local isolation point. These connectors are only marginally more expensive than plain connectors and pay back the cost in reduced call-out time on future service visits.

Built-in isolation valves are available for 15 mm × 1/2", 15 mm × 3/4", and 22 mm × 3/4" connections. The isolating mechanism is typically a slotted-head quarter-turn valve body; some brands use a colour-coded handle (red for hot, blue for cold).

Monobloc Tap Tails

Monobloc mixer taps — the single-hole kitchen sink mixer or basin mixer — do not use standard 1/2" BSP tap tails. They have machine-thread tails, most commonly M10 (10 mm metric thread) or M12 (12 mm metric thread). These are a pair of thin stainless tails that pass through the single hole in the sink or basin deck before flaring into flexible connectors that accept a 15 mm compression fitting.

Monobloc tap tails are always sold in pairs (hot and cold). Standard length is 300 mm; 500 mm tails are available for deep undermount sinks. When replacing a monobloc, check whether the replacement tap comes with its own tails — many budget taps do not include them, and fitting the wrong thread size will cause immediate leaks.

Push-Fit Flexible Tap Connectors

Push-fit flexible tap connectors (15 mm push-fit × 1/2" or 3/4" BSP) are available where solvent or compression joints are not possible — for example on plastic-pipe supplies (Speedfit or Hep2O) or in extremely restricted spaces. The push-fit end grips the outside of 15 mm pipe in the same way as a push-fit elbow or coupling. These cost more than compression connectors and should be used where the compression option is impractical, not as a default.

Installation Tips

• Isolate the supply before disconnecting any existing connectors — even if the tap appears dry, residual pressure in the supply line will cause water hammer or splash when the fitting is broken.
• Support the tap tail during tightening. Kitchen monobloc taps are not always secured tightly to the sink deck, and torquing against the tap body will rotate the whole tap.
• Do not use excessive PTFE on 1/2" BSP tap tails — three turns is adequate. Excess PTFE can cause the nut to cross-thread.
• Check for drips at both ends on first pressurisation, not just the compression end. Tap tail connections are a common source of slow under-sink leaks that go unnoticed for months.
• When replacing a connector with built-in isolation valve, mark the hot side with red tape or a red marker before closing the cupboard — future tradespersons and homeowners will thank you.

Flexible Tap Connectors at APM Electricals

Browse our full range of plumbing fittings and plumbing supplies at APM Electricals.

APM Electricals — 24 Western Avenue, Acton, London W3 7TZ
Call us: 020 8702 8080 | www.apmi.uk