What to ask before hiring a plumber: a 7-point checklist

Why a checklist matters

Most plumbing problems are time-sensitive. A leaking pipe, a broken boiler in November, a blocked drain — these are jobs you want fixed today, not Wednesday. That urgency is exactly when people stop asking questions and just book the first plumber who picks up.

The seven questions below take three minutes on the phone. They protect you from the small number of bad bookings that turn one £150 repair into a £600 repair plus a small claim.

1. Are you a member of a trade body?

For most plumbing work this means CIPHE (the Chartered Institute of Plumbing and Heating Engineering) or APHC (Association of Plumbing and Heating Contractors). For anything involving a gas appliance — boiler, gas hob, gas fire — it must be Gas Safe Register. That is not optional. Working on gas without being Gas Safe registered is illegal.

You can verify a Gas Safe number for free on the Gas Safe Register website. Take the plumber's name and registration number on the phone and check it before they arrive. The check takes 30 seconds.

For electrical work that touches a plumbing job (an immersion heater, an electric shower), the relevant body is NICEIC or NAPIT, not Gas Safe.

A plumber who is not in any trade body is not automatically bad — many sole traders work outside the schemes. But you then need them to be stronger on points 2 and 3 below.

2. Do you have public liability insurance? For how much?

The standard cover is £2 million. £1 million is the floor. Less than £1 million, or "I'll have to check", is a polite signal to keep looking.

Public liability covers their mistake damaging your property. It does not cover the quality of the work itself — that is a separate "workmanship guarantee", which not every sole trader offers.

If they say yes, ask for the insurer's name. A plumber who knows their insurer (Aviva, Hiscox, Tradesman Saver, etc.) has a real policy. A plumber who hesitates may not.

3. What is your policy on parts?

There are three honest answers:

• "I bring common parts in the van; anything specialist I source and add to the bill at cost plus 15%." This is the standard.
• "I bring the parts and bill at trade plus 20%." Also standard. Slightly less transparent but normal.
• "You buy the parts, I fit them." Fine for simple jobs (a tap, a toilet seat) where you can buy the right thing. Not fine for boilers, where the wrong part wastes a day.

What you do not want is "I'll let you know the bill afterwards." Get a parts policy on the phone before they arrive.

4. What is the call-out fee, and what does it include?

This is the single most common source of bill surprise. Ask explicitly:

• Is there a flat call-out fee separate from the labour rate?
• How much is the first hour?
• How is partial-hour time billed after that (rounded up to the next 15 minutes, the next half hour, the next hour)?
• Does the call-out cover the diagnosis, or only the visit?

A typical 2026 answer in London is "£75 call-out which includes the first hour, then £55 per additional hour, billed to the nearest 30 minutes." A typical answer in a smaller town is "£45 call-out, £40 an hour after that."

Get the answer on the phone. Get it in writing in the message or email confirming the booking.

5. When can you come, and how long will you be?

Two parts. "Tomorrow morning" is one answer. "Tomorrow morning between 9 and 12, and I expect the job to take two to three hours" is the answer you want.

A plumber who books a tight window and is honest about overrun is more reliable than one who promises 8am and turns up at 2pm. If they say "I'll fit you in", they mean "you are not a priority booking" — which is fine if you are not in a hurry, but you should know.

Ask if they can call 20 minutes before they arrive. Most will.

6. What happens if it does not fix the problem?

Most boiler and pipe diagnoses are right the first time. A small number need a second visit because the symptom pointed at the wrong cause. Ask:

• If the part you fit does not solve the issue, do I pay for the second visit?
• If a fitted part fails within a month, is it covered?
• What is your workmanship guarantee — 12 months is the trade standard for most pipework and fittings.

A confident plumber will offer 12 months of workmanship cover on most jobs without prompting. A plumber who refuses to guarantee their own work is one to skip.

7. Can I have it in writing?

Once the job is agreed on the phone, ask for a short written confirmation by email or message that contains:

• The address, date and time slot
• The job description in one sentence
• The agreed call-out fee and hourly rate
• The parts policy
• The workmanship guarantee period
• Their full name and Gas Safe or trade body number

A working plumber sends this in two minutes from their phone. A plumber who refuses or makes excuses is creating future ambiguity on purpose. That is the moment you go back to the search results.

A note on emergencies

In a true emergency — a burst pipe pouring water onto a downstairs ceiling, a smell of gas, no hot water in winter — the rules bend. You may pay a 50–100% premium for a same-day or overnight visit, and you may not have time for all seven questions.

In that case, do points 1, 2 and 4 as a minimum:

• Are you Gas Safe (or trade body) registered?
• Do you have public liability insurance?
• What is the emergency call-out fee?

The other four questions can wait until the immediate leak is stopped.

Using the checklist on HeroTasker

When you post a plumbing task, contractors reply with a price and a short pitch. You can ask all seven questions in the Questions tab on the task page — and other bidders will see the answers. That tends to filter quickly.

Most reputable plumbers welcome the questions. The ones who do not are the ones the checklist is for.