What Actually Happens When We Fit a New Boiler

A standard boiler swap takes one day. We generally arrive between 8 and 9, drain the system down, and your heating and hot water are off from roughly mid-morning until late afternoon. The old boiler goes with us, the room gets cleared up, and we run through the controls with you before we leave.

If you've never had a boiler fitted before, the day itself is the bit nobody explains. You've agreed a price, booked a date, and now you're wondering whether you need to take the day off and what state the kitchen will be in by teatime.

Here's the whole thing, start to finish.

Before the day

We'll have already been round to look at the job, so there shouldn't be any surprises.

A few days beforehand, it's worth clearing the cupboard or the space around the boiler. If it's in a kitchen cupboard, empty it. If it's in a loft, we'll need the ladder down and a clear route to it.

You don't need to do anything else. We bring the boiler, the fittings and the dust sheets.

What to sort out yourself

If you've got pets, plan where they'll be. Doors get propped open, and there'll be people going in and out.

If anyone in the house needs hot water at a set time - a baby, someone unwell, shift work - tell us when we book, not on the morning. We can usually work around it if we know.

The morning

We'll normally arrive between 8 and 9 and start by putting sheets down and protecting the floor.

The first proper job is isolating the gas and water and draining the system. That's when the heating and hot water go off. On a standard swap, that's usually somewhere between 9.30 and 10.30.

Then the old boiler comes off the wall. This is the noisiest part of the day, and it's over fairly quickly.

The middle of the day

The new boiler goes up, and the gas, water and condensate connections get made. If any pipework needs altering to suit the new unit, this is when it happens.

If the system needs a chemical flush or a magnetic filter fitting, that goes in at this stage too. It's worth having - most manufacturer warranties expect the system to have been cleaned, and a filter catches the sludge that would otherwise end up back in the new boiler.

This is the quiet part. Fair bit of standing about while things fill and pressurise.

The afternoon

The system gets refilled, vented and pressure-tested, then we fire the boiler and run through the commissioning checks the manufacturer requires.

Radiators get balanced so the ones furthest from the boiler heat up properly rather than staying cold while the ones nearest cook.

You'll usually have hot water back by mid-afternoon and full heating not long after.

Before we leave

Three things happen at the end, and none of them should be rushed.

We show you the controls. How to set the timer, what the pressure gauge should read, and what to do if it drops. Two minutes now saves a phone call in November.

We clear up. Old boiler, packaging and any offcuts go with us. Sheets come up, floors get swept.

You get your paperwork. The Gas Safe certificate, the warranty registered in your name, and the building control notification - which is a legal requirement on every boiler installation and something you'll be asked for when you sell the house.

When it takes two days instead of one

Three jobs regularly run over into a second day.

Moving the boiler to a different room means new gas, water and flue runs, which is a job in itself.

Converting from a cylinder system to a combi means taking out the cylinder and the loft tank and reworking the pipework. Nearly always two days.

Older properties occasionally turn up something behind a panel that nobody could have seen - corroded pipework, an old fitting that has to be replaced. If that happens, we'll stop and talk to you about it rather than pressing on and adding it to the bill.

Frequently asked questions

How long will the heating and hot water be off? On a standard swap, roughly six to eight hours during the working day. You'll normally have hot water back mid-afternoon.

Do I need to be there all day? No. Someone needs to let us in, and it helps if you're around at the end for the handover, but you don't need to sit with us.

Will it be messy? There's some dust when the old unit comes off. We sheet up first and clear up after. Floors go back the way we found them.

Can you fit it in winter? Yes, and we do. Just be aware that the house will be cold for most of the day, so it's worth having a plug-in heater in whichever room you'll be sitting in.

What if something goes wrong afterwards? Ring us. The boiler carries its manufacturer warranty, and our work is certificated. Most first-week issues are a pressure setting or a timer question and take a phone call to sort.

Booking your new boiler in

If you're at the stage of getting quotes, it's worth asking each firm to talk you through the day the way we just have. How someone describes the work tells you a fair amount about how they'll do it.

We'd be happy to come and take a look and give you a straight answer. Call 020 8087 0799 or get in touch here.