Boilers · 4 min read
How long does a boiler installation actually take?
Day by day for a like-for-like swap, a conventional-to-combi conversion and a full system upgrade — plus the five things that actually make a job overrun.
Like-for-like combi swap: one day
Same location, same fuel, same boiler type. Old unit out in the morning, new unit in and commissioned by the afternoon, controls demonstrated before we leave. You are without heating and hot water for most of the working day.
Conventional to combi conversion: two days
Removing the tank in the loft and the cylinder in the airing cupboard, re-routing pipework and making good takes the extra day. Day one is strip-out and first fix; day two is the boiler, commissioning and testing.
System upgrade: two to three days
Where the boiler is being replaced alongside radiator changes, zoning, smart controls or a new unvented cylinder. Doing it in one visit is significantly cheaper than doing it in two.
What causes overruns
In our experience it is nearly always one of a short list, and nearly all of them are avoidable with a proper survey.
- Flue routing that cannot be confirmed until the old unit is off the wall.
- Gas supply pipe too small for the new appliance's rate.
- A heavily contaminated system that needs a power flush before commissioning.
- Asbestos in older flue or boiler housings.
- Electrical work needed that the installer is not qualified to do. This one does not apply to us — we are an NICEIC Approved Contractor and carry out our own electrical work.
Questions we get asked
Will I be without hot water overnight?
On a one-day swap, no. On a two-day conversion, usually for one night. We tell you which applies before the job starts.
What warranty comes with the installation?
Up to 18 years on ATAG boilers, plus a 2 year workmanship warranty on every BBI installation as standard.
Want this checked against your own property?
A survey costs nothing and turns general advice into specific numbers. We are Gas Safe, NICEIC and MCS accredited (NIC601962), so whichever direction the answer points, the same team can do the work.
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Read guideReady to get started?
Tell us about your property and we will come back with a written, itemised quotation — not a phone estimate.