Dodgy tradespeople are everywhere — but the right questions upfront will protect your money and your home. Here's exactly what to ask before you book.
Finding a good plumber in Croydon sounds simple. It isn't always. The plumbing trade is unregulated for basic plumbing work, which means anyone can legally call themselves a plumber — no qualifications, no checks, no accountability. The result is a wide spectrum of quality, from first-class tradespeople to outright rogues.
The good news is that asking the right questions before you hire protects you almost entirely. Here are the eight questions that matter most.
This one is non-negotiable for any gas work. Gas Safe registration is a legal requirement in the UK for anyone working on gas appliances, pipework or flues. It is not optional, not voluntary, and not the same as being "CORGI registered" (CORGI was replaced by Gas Safe in 2009). Ask to see the physical Gas Safe ID card — it carries a licence number you can verify at gassaferegister.co.uk.
For general plumbing (taps, toilets, pipes, drains) there is no equivalent mandatory registration, but reputable plumbers often hold CIPHE, WaterSafe, or APHC membership as voluntary indicators of training and professionalism.
🚩 Red flag: carries out gas work without being able to produce a Gas Safe ID cardA plumber working in your home should carry public liability insurance — typically £1 million minimum, ideally £2 million or more. This covers accidental damage to your property during the job. Ask for the certificate, check the expiry date, and make sure the level of cover is adequate. A reputable tradesperson will have this readily available and will not be offended by the request.
🚩 Red flag: claims not to need insurance, or cannot produce documentationA written quote locks in the price and protects you if a dispute arises later. It should specify the scope of work, the materials being used, labour costs, and any call-out or visit fees. If a plumber insists on a verbal quote only — or refuses to commit to a price until they've started the job and uncovered something — that is a significant red flag. Legitimate tradespeople work on agreed prices, not vague estimates that balloon mid-job.
🚩 Red flag: refuses to quote in writing, or won't give a price until work has startedAsk for their Google Business profile name, or look them up on Checkatrade or Trustatrader. Reviews that name specific jobs and locations are far harder to fake than generic five-star comments. Pay attention to how the business responds to any negative reviews — a measured, professional response to a complaint tells you more about a company's character than a wall of five-star ratings. For Croydon-specific plumbers, look for reviews mentioning local areas like Thornton Heath, Purley, Sutton, or Bromley.
🚩 Red flag: no online presence, no verifiable reviews, or all reviews are very recent with no historyA reasonable deposit for a small job is zero. For larger jobs requiring specialist parts or materials, a deposit of up to 25–30% on acceptance of the quote is reasonable. Never pay in full before work begins. Never pay cash only with no receipt. Any insistence on full payment upfront — particularly for a job you haven't agreed to in writing — should be treated as a serious warning sign.
🚩 Red flag: demands full payment upfront, insists on cash only, or will not provide a receiptCertain plumbing and heating work — including new boiler installations, replacing a gas supply pipe, and some bathroom installations involving electrical work — requires notification to your local building control authority under Part G and Part P of the Building Regulations. A Gas Safe registered engineer can self-certify their own gas work. For other notifiable work, your plumber should either notify building control themselves or arrange for you to do so. Skipping this step creates problems when you come to sell the property.
🚩 Red flag: dismisses building regulations as unnecessary for notifiable workThis matters more than it might seem. A plumber genuinely based in or near Croydon can respond faster to emergencies, knows local water pressure quirks (Thames Water supply in South London has specific characteristics), and has a local reputation to protect. A plumber travelling from far afield for a quoted job may be cheaper on paper but less available if a follow-up call is needed. Ask where they're based and how quickly they can typically reach your area.
It sounds obvious, but it's worth asking. Plumbing work often involves accessing pipes under floors, in wall cavities, or beneath kitchen units — creating significant mess in the process. A professional plumber will protect the surrounding area before starting, work tidily throughout, and leave the space in a clean state when they're done. If a previous plumber left a mess and disappeared, you'll know why this question matters.
Personal recommendation from a neighbour or friend who has had recent plumbing work done is still the most reliable source. Beyond that:
Emergency plumbing is where the rogues concentrate. When water is gushing through your ceiling at midnight, the temptation is to call the first number that comes up. Prices in genuine plumbing emergencies are legitimately higher because of unsocial hours and the need to drop other work — but some "emergency plumber" services charge extreme rates and deliver poor work under that pressure.
The best defence is to save the number of a plumber you've already vetted before you need them in a crisis. For Croydon and South London, that means having a number you can rely on before the pipe bursts, not after. If you're caught in an emergency without a number, ask the plumber to confirm their call-out rate and hourly rate before agreeing to anything, and insist on a written confirmation even if it's just a text message.
In a burst pipe situation, the first thing to do is always find and turn off the main stopcock — usually under the kitchen sink, in the airing cupboard, or near the water meter — to stop the flow. Then make the call from a position of control rather than panic.
Nas Plumbing is Gas Safe registered, fully insured, and based locally in Croydon. Written quotes, clear pricing, no hidden costs. Call us or send a message to get a free quote.
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