Renovation & New Build

Extension Plumbing

We take water, heating, gas and drainage out into your new extension and tie it back into the house so the whole property still performs properly. First fix while the shell is open, second fix once it is plastered, and a new bathroom or kitchen fitted in the same run of work if you want one.

Call 01273 911551
Concealed shower valve first fixed to a backing board with copper pipework and a laser level lineConcealed shower valve first fixed to a backing board with copper pipework and a laser level line

What's involved

From the first pipe run into the new shell to the last fixture connected, here is what extension plumbing usually covers.

First Fix Into the New Shell

Water, waste and heating pipework run through the extension before plastering and screeding, then capped and pressure tested.

Tying Into the Existing System

New pipework connected back into the existing supplies and drainage, with pressure, pipe sizing and falls checked first.

Heating the New Space

Radiators or underfloor heating extended into the extension, and honest advice on whether the boiler or cylinder needs to grow with it.

Bathrooms and Kitchens

Second fix sanitaryware, showers, sinks and appliances installed, connected and commissioned once the finishes are in.

Plumbing an extension so the whole house still works

An extension is rarely just a new room. It usually means another basin or two, often a shower, sometimes a kitchen moving into the new space, and always more demand on a heating and hot water system that was sized for the house as it was. The plumbing has to serve the new rooms and leave the old ones performing as well as they did before.

That is the part people underestimate. Running pipework into a new shell is straightforward; keeping the shower upstairs behaving once a second bathroom is drawing off the same main is where the thinking goes.

Extending a house means extending the system, not bolting a room onto it.

Before anything is run

We start with what you already have. That means checking the incoming mains, the pressure and flow actually available, the size of the existing pipework, what the boiler or cylinder can realistically carry, and where the existing drainage runs and at what depth.

Those findings shape the design. If the extension adds a bathroom, the hot water side may need to grow with it; if it adds a kitchen, the waste has to reach an existing run with enough fall to drain quietly. Far better to find that out with the plans on the table than with the floor already down.

First fix

Once the shell is up and watertight, the hidden work goes in. Hot and cold supplies are run on routes that stay clear of the structure, waste and soil pipes are set with proper falls and vented correctly, and heating flow and return lines are taken out to each radiator or underfloor manifold position.

Where a boiler is moving into the extension, or a hob is going into a new kitchen, the gas pipework is run at this stage. That work is domestic, and it is carried out under our Gas Safe registration, 568345.

Everything is then capped, pressure tested and left under pressure before the plasterers or screeders go anywhere near it.

More information

Things worth deciding early

  • Whether the extension includes a bathroom, en-suite or utility, and where the soil connection will be
  • Whether the existing boiler and cylinder can carry the extra demand
  • Radiators or underfloor heating, since underfloor has to be planned before the screed goes down
  • Where isolation valves and access points should sit for future maintenance
  • Whether the kitchen is moving, and where its waste and supplies need to land
  • How long the house can sit without water or heating while the new work is tied in

Tying in, and second fix

Connecting new to old normally means draining the system down for a spell. We tell you in advance when that will be and roughly what it involves, so you can plan around it rather than discover it on the day.

After plastering, tiling and units, we come back to fit and connect: sanitaryware, taps, showers, radiators, the cylinder, appliances and controls. The system is then refilled, vented, leak checked and balanced across the whole house rather than just the new part, because the original radiators share the same pump and the same flow.

A good tie-in is one you cannot find afterwards.

We are based in Woodingdean and cover Brighton, Hove, Worthing, Lewes, Shoreham-by-Sea, Haywards Heath, Seaford, Burgess Hill and surrounding Sussex towns. If your extension includes a bathroom, that is our speciality: we design and install them end to end.

Before you book

Straight answers to the questions homeowners ask us before an extension gets under way.

What is the difference between first fix and second fix on an extension?
First fix is the hidden pipework for water, heating, gas and drainage, installed once the shell is watertight and before plastering and tiling. Second fix is fitting and connecting everything visible afterwards: radiators, the boiler, taps, sanitaryware and kitchen appliances. The two stages sit either side of the plasterer, so they are separate visits.
Will an extension need a bigger boiler or hot water cylinder?
It depends on how much extra demand the new space adds, and an extra bathroom adds far more than a downstairs cloakroom. We look at the existing boiler and cylinder, the incoming mains and the number of outlets, then tell you plainly whether an upgrade is needed. We are an accredited Vaillant installer if a new boiler turns out to be the sensible option.
Can new pipework connect to the plumbing already in the house?
Yes. Tying the new work into the existing supplies, heating circuit and drainage is a core part of the job. We check pressure, pipe sizing and drainage falls before the new layout is designed, so the original bathrooms and radiators still perform properly once everything is connected.
Will we lose water or heating while the new pipework is tied in?
There is usually a period where the system has to be drained down so the new pipework can be connected. We agree when that will happen and give you a clear idea of what it involves, so you can plan around it. It is normally the only real disruption in the whole job.
Can you run gas pipework for a boiler or hob in the extension?
Yes. We are Gas Safe registered for domestic gas work, registration 568345, so gas pipework to a boiler or to a new kitchen hob can be run at first fix and connected at second fix. All of our gas work is domestic.
Can you fit the bathroom in the new extension too?
Yes. Complete bathroom design and installation is our speciality, so an en-suite or family bathroom in the extension can be designed and fitted as part of the same project. That keeps the soil connection, the wastes and the service points matched to the layout you actually want.
Which areas do you cover for extension plumbing?
We are based in Woodingdean and cover Brighton, Hove, Worthing, Lewes, Shoreham-by-Sea, Haywards Heath, Seaford, Burgess Hill and surrounding Sussex towns. If your extension sits a little outside that, it is still worth asking.
How do we get a quote for extension plumbing?
Call us on 01273 911551 with your plans to hand, or come and see us at 58 Warren Road in Woodingdean. We will go through what the new space will contain, what your existing system can carry, and how the work splits between first and second fix, then price it from there.

Let's sort the plumbing for your extension

Tell us what the new space will contain and we'll talk you through how it should be plumbed.

Call 01273 911551