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Installation

What Happens During a Boiler Installation? A Day-by-Day Account

Never had a boiler installed before? Here's a detailed account of exactly what to expect on installation day.

10 May 2025·7 min read·By Corby Boiler Installations

What to Expect on Boiler Installation Day

8:30am — Engineer Arrives

Your Gas Safe engineer introduces themselves, shows their ID, and does a brief survey of the existing boiler and heating system before starting work.

9:00am — Draining Down

The heating system is drained down. This takes 20–40 minutes and involves turning off the water supply and draining radiators and pipes. Your heating and hot water will be off from this point.

10:00am — Old Boiler Removed

The old boiler is disconnected from gas, water, and electrical supplies and removed. The engineer checks the flue route for the new boiler and makes any necessary adjustments.

11:00am — New Boiler Installed

The new boiler is mounted and connected to the gas, water, and electrical supplies. The new flue is fitted through the wall or roof.

1:00pm — System Filled and Tested

After lunch, the system is filled with water, a corrosion inhibitor added, and the system pressure set. All connections are checked for leaks.

2:00pm — Testing and Commissioning

The boiler is fired up and all radiators tested. The programmer and thermostat are set up and you're shown how to use them.

3:00pm — Handover

The engineer issues your Gas Safe certificate, boiler registration documents, and warranty information. They walk you through everything before leaving.

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