What Happens on the Day Your New Boiler Is Fitted

On the day your new boiler is fitted, the engineer arrives in the morning, protects your floors, drains the heating system, takes the old boiler off the wall, fits the new one with its flue and pipework, cleans the system, fills it back up, tests everything, shows you how the controls work and leaves you with the paperwork. For a straightforward like for like combi swap that is normally one day. A conversion from a cylinder and tanks, a back boiler removal or a boiler that is moving to a different room takes longer, and we tell you that before we book it. Here is what actually happens, hour by hour, so there are no surprises.

Before the day

By the time we arrive, the hard thinking has already been done. You will have had a fixed price, either from the online quote tool or from a visit, and a free survey where the engineer who is doing the job has checked the flue route, the gas supply, the condensate drain and where the boiler is going. Nothing on the day should be a shock to either of us.

A few things help the day go smoothly:

• Clear the space around the old boiler and the route to it, including the cupboard beneath if it is in the kitchen.
• Move anything precious from the room the boiler is in and, if the flue is changing, from below the outside wall.
• Make sure we can get to the gas meter and the stopcock.
• Expect to be without heating and hot water for most of the day. Fill the kettle and run a bath the night before if you want one.

Arrival and protection

We arrive in the morning and start by laying dust sheets and floor protection along the route from the van to the boiler. Boiler jobs create dirty water and dust, and the reviews people leave about a job being clean and tidy come down to what happens in these first twenty minutes. Then we isolate the gas, the water and the electrics to the old boiler.

Draining down and taking the old boiler off

The heating system is drained, which takes a while on a bigger house because every radiator has to empty. If we are removing a cylinder and loft tanks as part of a conversion, those come out now, and you get an airing cupboard back. The old boiler is disconnected and lifted off the wall. If a back boiler is coming out, the fire comes out first, then the boiler behind it, and the opening is made safe.

Fitting the new boiler

The new boiler goes up on its bracket, and this is where the survey pays off. If the flue is going through the same hole, the job moves quickly. If today's rules mean the flue needs a new position, a plume kit or a run through the roof, that was priced and planned in advance, so it is simply part of the day rather than a problem. The gas pipe is checked for size and connected, the heating flow and return, the cold feed and the hot water outlet are connected, and the condensate pipe is run to a drain, ideally inside the house so it cannot freeze.

A magnetic filter goes on the return pipe as standard. It catches the sludge that would otherwise settle in the new boiler, and it is the single cheapest thing that makes a boiler last.

Cleaning and filling the system

A new boiler on a dirty system is asking for trouble, so before it runs for real, the system is cleaned. On most jobs that means a chemical cleaner circulated through the radiators and then flushed out. If the survey showed the system was badly sludged, a full power flush may have been included in your price. The system is then refilled, inhibitor is added to protect the metal inside, and every radiator is bled.

Commissioning and testing

This is the part people do not see but matters most. The engineer checks the gas rate and pressure, tests the flue gases with an analyser to confirm the boiler is burning cleanly and safely, checks for gas leaks and water leaks, and runs the heating and the hot water to make sure everything does what it should. The settings are adjusted for your house, including the flow temperature, which makes a real difference to how much gas a modern boiler uses.

Showing you the controls

Before we pack up, we walk you through the boiler and the controls. How to read the pressure gauge and top it up, how to set the programmer or thermostat, what the display shows if something goes wrong, and where the condensate pipe comes out so you know what to check if it ever freezes. Ask as many questions as you like. Ten minutes now saves a phone call in December.

The paperwork

You should end the day with three things. The Benchmark checklist in the boiler manual filled in and signed, which is the record of how the boiler was commissioned. Your Building Regulations compliance certificate, which comes through after we notify the installation through Gas Safe Register. And your manufacturer warranty, which we register in your name. The warranty depends on an annual service, so the first service date goes in the diary too.

What if something is not right?

Occasionally a radiator needs another bleed once the system has settled, or the pressure drops a touch in the first few days as the last of the air works its way out. That is normal. If anything does not seem right, ring us. We would far rather come back and check than have you living with something that bothers you.

The full detail of the boilers we fit and how we work is on our new boiler installation page. If you are comparing local options, go straight to new boilers in Houghton le Spring, new boilers in Sunderland, new boilers in Durham or new boilers in Washington. Our cost guide explains what moves the price.

Frequently asked questions

How long does it take to fit a new boiler?

A combi replacing a combi in the same position is normally done in a day. Converting from a cylinder and tanks to a combi, moving the boiler to another room or removing a back boiler takes longer, and we tell you how long when we give you the price.

Will I have hot water on the day?

Not for most of it. The water and gas are off while the old boiler comes out and the new one goes in. By the time the engineer leaves, heating and hot water are running and tested.

Do I need to be at home?

Somebody needs to let us in and be there at the end for the walk through and the paperwork. You do not need to stand over us all day.