Boiler pressure and heating faults
Most combi boilers run best between 1 and 1.5 bar of pressure — too low and the heating cuts out, too high and the pressure relief valve can discharge. A plumber checking a heating fault will usually look at pressure, check for trapped air in radiators (bleeding), and check the pump and diverter valve before assuming a full boiler fault.
Do you know where your stopcock is?
Every property has a main stopcock (usually under the kitchen sink, though sometimes in a different location in older or converted properties) that shuts off the water supply. Knowing where it is and checking it turns freely, before you need it in an emergency, is one of the simplest things a homeowner can do.
What affects the cost
Cost depends on the scope of the job, how accessible the pipework is (under a floor vs behind a wall), whether parts need to be sourced specially, and whether the job is planned or an emergency call-out. A simple tap or valve replacement is usually quick and low-cost; anything requiring pipework to be rerouted, or walls/floors to be opened up, costs more partly because of the making-good work afterwards.
What is a power flush and do you need one?
A power flush clears sludge and debris from a central heating system's radiators and pipework using a pumped chemical flush — usually recommended if radiators are cold at the bottom, or before installing a new boiler onto an older system, so the new boiler isn't immediately clogged by old sludge.
Aftercare after plumbing work
After a boiler installation or bathroom refit, you should receive a benchmark/commissioning checklist (for a boiler) or a written summary of the work done, which you'll want if you make an insurance claim or sell the property later. Keep it with your household paperwork alongside any appliance warranties.
When plumbing work needs a Gas Safe engineer instead
Plumbers can install and repair most water systems, but any work on a gas appliance or gas pipework — a boiler, a gas fire, a gas hob — is illegal for anyone who isn't on the Gas Safe Register, by law. If a job involves both plumbing and a gas connection (moving a boiler, for example), check whether your plumber is also Gas Safe registered before booking.
Three steps to hiring the right plumber
First, check they're registered with a WaterSafe scheme (or Gas Safe too, if the job needs it) and ask for the registration number. Second, get a written quote that separates labour from parts. Third, ask what happens if the job uncovers a bigger problem — a good plumber will tell you before continuing, not after.
Red flags in a cheap plumbing quote
A quote significantly below the others is worth questioning before accepting — check it specifies the same quality of parts (a boiler make/model, not just "a boiler"), includes making good after any pipework is exposed, and covers testing before the job is signed off as complete.