12 Questions to Ask Before Hiring a Plumber
A good plumber can save you thousands by diagnosing problems correctly and fixing them first time. A bad one can cause flooding, gas leaks, or leave you with work that fails within weeks. These 12 questions help you tell the difference — before you hand over your keys.
Our in-house team of qualified, insured plumbers covers all of NW London.
Get a Quote1.Are you registered with a professional body?
Membership of the Chartered Institute of Plumbing and Heating Engineering (CIPHE), or listings on WaterSafe (the UK plumber finder backed by water companies) indicate professional standards.
Yes — here is my registration number. You can verify it online.
Hesitation, inability to provide a registration number, or dismissing the question.
2.Are you Gas Safe registered? Can I see your card?
ANY work on gas pipes, boilers, or gas appliances MUST be done by a Gas Safe registered engineer. It is a legal requirement. Non-registered gas work is illegal and dangerous.
Yes — here is my Gas Safe card. The number is X, you can check at GasSafeRegister.co.uk.
Claiming Gas Safe is unnecessary, offering to do gas work without registration, or showing an expired card.
3.Do you have public liability insurance?
If a plumber causes accidental damage to your property (flooding, broken tiles, damaged walls), their insurance covers the repair. Without it, you pay.
Yes, I carry £2 million public liability insurance. I can show you the certificate.
No insurance, claiming they have never had a claim so do not need it, or inability to show proof.
4.Can you give me a fixed written quote — not an estimate?
A quote is a fixed price. An estimate can change. Without a written quote, you have no protection if the final bill is double what you expected.
Yes — I will assess the job and provide a written fixed-price quote before starting work.
Insisting on day rates for a defined job, or saying they cannot quote until they start.
5.What is included in the quote — and what is not?
The most common billing disputes arise from misunderstandings about what is and is not included. Materials, waste removal, making good — confirm everything upfront.
The quote includes labour, materials, and making good. Anything additional will be agreed with you before proceeding.
Vague answers, or discovering extras on the final invoice that were not discussed.
6.How long will the job take?
A professional should be able to estimate duration based on the scope. If they say a day, hold them to it. Overruns cost money and disrupt your life.
Based on what I can see, this should take X hours/days. If I find anything unexpected, I will let you know before continuing.
Cannot give any estimate, or history of jobs taking much longer than quoted.
7.Can you provide references or examples of similar work?
A plumber who has done similar work successfully can show you photos, reviews, or connect you with past clients. Experienced professionals are proud of their track record.
Here are photos of a similar job I completed last month. I can also give you a client reference.
No references, no photos, or claiming they do not keep records of past work.
8.Do you guarantee your work? For how long?
A guarantee means the plumber will return to fix any problems with their work at no additional cost. Industry standard is 12 months.
All my work is guaranteed for 12 months. If anything I have done fails, I will come back and fix it free of charge.
No guarantee offered, or a very short guarantee period (less than 6 months).
9.Will you provide a written invoice and any certificates?
You need documentation for warranty claims, insurance, and future reference. Gas work requires a Gas Safe certificate. Electrical work needs Part P certification.
Yes — you will receive a detailed invoice and any relevant safety certificates on completion.
Offering a cash discount to avoid invoicing, or not mentioning safety certificates for gas work.
10.What happens if you find a bigger problem during the job?
Plumbing often reveals hidden issues — corroded pipes, failed valves, or unexpected configurations. How this is handled determines whether you get a surprise bill.
I will stop work, show you what I have found, explain the options, and give you a revised quote before continuing.
Doing additional work without asking and billing for it afterwards.
11.Do you clean up after the job?
A professional plumber leaves your home as they found it — or better. Dust sheets, cleaning up, removing old parts — this is part of the job.
Of course — I always clean up and remove any waste. I will leave the area tidy.
Leaving mess, old parts, or packaging behind for you to deal with.
12.When can you start — and will you actually turn up?
Reliability is the number one complaint about tradespeople. Confirm the start date, arrival time, and how they will communicate if delayed.
I can start on X date. I will arrive between X and X. If I am running late, I will call you.
Vague timing, history of no-shows, or inability to commit to a date.
Skip the research — our team is ready
Every plumber at Hampstead On Demand is qualified, insured, and experienced with NW London properties. We do the due diligence so you do not have to.
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