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.
Combi vs system vs conventional boilers
A combi boiler heats water on demand with no separate tank, suits smaller properties with one bathroom. A system boiler uses a hot water cylinder but no cold water tank, better for higher demand. A conventional (regular) boiler uses both a cylinder and a tank, common in older properties and useful where mains pressure is poor.
What a good plumbing quote should include
A proper quote should state the scope of work, whether parts are included in the price or charged separately, an estimate of how long the job will take, and what happens if the job turns out to be bigger than expected once work starts (a common scenario with older pipework).
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.
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.
Plumbing in older and period properties
Older properties sometimes still have lead or galvanised steel pipework, which can affect both water quality and pressure, and original layouts weren't designed around modern demand for multiple bathrooms. A plumber working on a period property will often check what the existing pipework is made of before quoting for anything beyond a like-for-like repair.
What a boiler fault code usually means
Modern combi boilers display a fault code when something's wrong rather than just stopping — the exact meaning varies by manufacturer, but common causes behind a "no heat" code include low pressure, a faulty sensor, or an ignition fault. Note the code before calling a plumber; it speeds up diagnosis considerably.
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.