Most people don’t think too much about their plumbing until something goes wrong. When it does, the need tends to be urgent, when the cost of fixing the problem is secondary. Because you didn’t act sooner, there might be associated costs that you could have prevented. Your relationships with neighbours may be damaged. You may have to make an insurance claim.
How much expertise do you really need? If you’re just changing a tap, not that much. But if you’re installing a whole-house system, you need someone with deep knowledge based on years of experience, who knows what questions to ask: How many people live here? How long will you stay in this house? How much can you afford? Have you considered a heat pump? What’s the water pressure? Is it enough to suit your needs? What exists? What can be left alone, and what needs updating?
Do you need to change your behaviour? A good plumber will tell you that you need a descaling regime in a hard water area, maybe a water softener. To stop emptying cooking fat down the sink and to start cleaning up dishwasher-blocking food debris before you begin stacking.
Planned, preventative maintenance is better than serial crises.
Good plumbers earn a lot of money. Ask anyone who works for Pimlico Plumbing. There’s a story, probably apocryphal, about a lawyer who, on receiving his invoice from a plumber, says: “Blimey, that’s more per hour than I earn as a lawyer.” The plumber replies: “That’s why I gave up my legal career.”
Get three quotes by all means. But choosing the cheapest is riskiest. Choosing the plumber who can start tomorrow is riskier still.
Does the plumber sound like they’re an expert? Do they listen to you and ask questions before jumping straight into the solution? Do they have five-star Google reviews? Are they happy to give you customer references?
Do they know about time or money-saving products? Push-fit plastic piping is cheaper than soldered copper and significantly easier to install. An expansion vessel on that pressurised hot water tank will quickly pay for itself with reduced water bills. Isolation valves on all taps and toilets are well worth the small additional cost.
If you get the chance, look in the back of their van. Is it chaotic or organised? Do they carry spares for common problems? Or do they always have to go off to find the part (and probably ask someone more experienced for advice) while charging you for that time?
Ultimately, would you recommend them to a friend or neighbour?
Footnote: what the hell do I know about plumbing? A little, from renovating several properties and because of my nerdy curiosity about technical things. Just don’t hire me as a plumber.