What plumbing does a boiling water tap need before first fix?

Three things have to be roughed in before walls close: a dedicated cold supply separate from the main sink cold, a 13-amp socket in the under-sink cabinet for the tank, and enough cabinet space for the tank, valves, and waste pipe. The tap itself is fitted at second fix, but the provisions cannot wait.

Do you need a separate drinking water tap if you fit a water softener?

Yes, this is a regulatory requirement, not optional. The Water Fittings Regulations require at least one tap drawing water from the supply before the softener, because softened water has raised sodium and should not be used for drinking or infant formula. That means a second cold stub upstream of the softener, provisioned at first fix.

Do dishwashers and washing machines need a hot water supply?

No. Almost every machine sold in the UK today is cold-fill only and heats water internally, so one cold stub with an isolating valve is the correct provision for each. The rare exception is a dual-fill model for solar thermal or heat pump systems, which needs a capped hot stub added at the position.

What plumbing does a fridge ice maker need?

A small-bore cold feed, roughly 8 to 10mm, run to the fridge location during first fix. It takes a plumber minutes while the walls are open, but the same job after plasterboard is up means chasing a pipe through a finished wall and making good, so run a capped feed even if the fridge is not bought yet.

Why does the kitchen service void affect first fix plumbing?

The void behind kitchen units varies by brand, and a tight void may not fit a standard 40mm waste pipe once fittings are added. If the rear space is too shallow, the plinth void becomes the route instead, which changes the height the stubs exit the wall, so your plumber needs the kitchen brand before roughing in.

Back to Kitchen Extension

Phase 6 · First Fix · Task 07 of 08

Kitchen Plumbing Provisions: What to Tell Your Plumber Before First Fix

The full list of kitchen-specific plumbing provisions your plumber needs before first fix starts: dishwasher and washing machine stubs, boiling water taps, water softeners, ice makers, and outside taps.

12 min readUpdated 2026Premium

Process infographic showing every kitchen plumbing provision as a grid checklist: sink, dishwasher, washing machine, boiling water tap, water softener bypass, ice maker cold feed, and outside tap, each with supply type and socket requirement

Prerequisites

Complete these first

Your plumber prices from a scope. If that scope misses the boiling water tap, the ice maker feed, or the water softener bypass, those become expensive extras added after walls close. A half-day becomes two days of disruption with plasterboard to repair. The first fix plumbing guide covers the mechanics. What follows here covers only what a kitchen needs.

What this guide covers

01Waste runs: what your plumber needs to know
02The full supply list: walk through every appliance
03Your kitchen's service void
04Boiling water taps
05Water softeners
06Outside tap
07Coordinate with the electrician at the same time
08The ice maker: the provision everyone forgets
09Put it in writing

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General guidance for homeowners in England (and Wales where we say so), not professional advice. Every site is different: check anything that affects your build with a qualified professional, your local council or building control. Terms

Frequently asked questions

Reference guides for this task

Free guides to the tools, materials and terms this step involves.