Questions to Ask a Plumber Before They Start Work

What does the call-out or attendance charge actually cover?

A good answer names a fixed figure, says how long it covers, and says what happens at the end of that period. A poor answer is a range, a from price, or a promise to work it out on the day. Know before anyone travels whether you are buying attendance alone, attendance plus diagnosis, or attendance plus a first block of working time.

The three models in common use get conflated constantly. Some firms charge a flat attendance fee covering the visit and the diagnosis only, with labour on top from the moment work starts. Some sell a first hour or two as one figure with everything inside it. Some quote per job, which only works when the job is already known, and on a fault call it is not.

None of those is dishonest. What matters is knowing which one you are buying before the van leaves. Ask the follow up too: if the engineer looks at it for ten minutes and says the part is obsolete and the unit needs replacing, what do you owe. If that answer is clear and unembarrassed, the business has had the conversation many times. If it goes quiet, you have found the part of the pricing that gets improvised on the doorstep.

• Is the charge for attendance only, or does it include a block of working time?
• How long is that block, and what is the rate after it?
• What do I pay if the fault is diagnosed but not repairable on the day?
• Is the charge different for evenings, weekends or out of hours?

How do you charge once the first period is used up?

The answer should be a single rate and a single billing increment, stated plainly: per hour, per half hour or per quarter hour. If the answer is that it depends, ask what on. The honest version of that answer exists, and it sounds like time on site and parts used, not like a shrug.

The increment matters more than people expect. Twenty minutes past the first hour costs very different amounts depending on whether the business rounds to the next quarter hour or the next full hour. Neither is wrong, but on a long repair those roundings compound.

Ask about waiting time and fetching time separately. If the stopcock in a converted house is seized or sits behind a neighbour, that time gets billed somewhere. If a part has to be collected from a merchant mid job, ask whether the trip is chargeable. A firm with an answer ready has thought about it. A firm without one decides on the invoice, and not in your favour.

Two different jobs can carry the same hourly figure and end up far apart on the total. What moves the number is access, isolation and whether the right parts were on the van. Those are the things worth discussing on the phone, not the rate itself.

Are you qualified for this specific job, not plumbing in general?

Plumbing is not one trade with one card. Gas work, unvented hot water storage and general plumbing are separate competencies with separate registration, so a competent plumber can still be the wrong person for your appliance. Ask which qualification the job needs, whether the attending engineer holds it, and for the registration number, then check it on the public register. Our guide on how to check a plumber on the Gas Safe Register walks through that lookup step by step, including what the card covers and what it does not.

The question does real work because the qualification tracks the risk. Sealed unvented cylinders store water above the temperature it would boil at atmospheric pressure, held there by a stack of safety devices, and anyone working on that stack needs to be competent in it specifically. A thermostatic shower valve needs none of that, and a firm reciting credentials at you over a shower cartridge is selling rather than answering. Unvented cylinder repair is the clearest example of the split, because the competency for it is held and registered separately from gas work, and a plumber can perfectly well hold one without the other.

A good answer is specific and slightly bored: yes, the engineer attending holds it, here is the number, check it. A bad one sounds like reassurance. Fully qualified, fully insured, all our engineers are experienced. Those phrases carry no information, because there is no register of being experienced. Where the job is a sealed cylinder, a G3 qualified plumber is exactly the person you want naming their own competency before you have had to ask twice.

• Gas appliance work: ask for the individual registration and check it on the public register.
• Unvented hot water cylinders: ask whether the attending engineer holds the unvented qualification.
• Anything on a communal or landlord owned system: ask who is permitted to work on it before booking.

Who is actually turning up, and do they work for you?

Ask whether the person attending is employed by the business you are speaking to or subcontracted through it. Both arrangements produce good work, but they behave differently when something goes wrong, and you want to know which you have before you need to know.

The practical difference is accountability and continuity. With an employed engineer, the business that took your money owns the outcome, keeps the job history and can send the same person back. With a booking platform or a lead broker, the firm you called may have passed the job on, so the person at your door may never have heard the description you gave on the phone.

The tell is simple. Ask what the engineer is called and whether the same person can return if the fault recurs. A firm with its own engineers answers at once. A broker cannot, because it does not know yet. That is a different business model rather than a scandal, but it should change what you expect from the aftercare.

What happens if the part is not on the van?

This is the most useful question on the list, because it decides whether your job takes one visit or three. Ask what the likely parts are for the symptom you described, whether they are carried as stock, and what a return visit costs if they are not. A good answer names the likely components before anyone has seen the job.

On a stored hot water system the wear items are the pressure reducing and expansion relief valves on the inlet group, the temperature and pressure relief valve on the vessel, the immersion element and its thermostat, and the motorised valve head. On a combi it is a diverter cartridge, a flow sensor or a plate heat exchanger. On a Pulsacoil style thermal store it is the pump, thermostats and control board, all model specific, which is why the data plate is worth photographing first.

Then ask about the return visit. If a part has to be ordered, do you pay a second attendance charge or labour only. Either answer can be fair. An unstated one never is.

• Which parts are likely for this symptom, and are they carried as stock?
• If the part is ordered, is the return visit charged as a fresh attendance?
• Are you fitting manufacturer parts or an equivalent, and which?
• What is the lead time on the part, and do I pay for it before it arrives?

Will you show me the fault before you replace anything?

Yes is the only acceptable answer, and the good version of it is enthusiastic. A failed component almost always shows why it failed. A scaled immersion element looks like a stick of rock, a passing relief valve leaves a trail, a seized motorised valve head will not hold its lever. An engineer confident in the diagnosis will put the old part in your hand and point at the evidence.

It matters most where the cause is invisible from the tap and the fix is expensive: a cylinder, a boiler, a leak under a floor. Ask what the diagnosis rests on before authorising work, then ask what would have to be true for it to be wrong. That second question separates a considered answer from a guess.

On leak work, ask how the leak was located rather than assumed. In a Victorian conversion with buried pipework, or a new build with liquid screed over underfloor heating, the gap between locating a leak and estimating its position is the gap between one neat access hole and a ruined floor. Lifting boards to look is a legitimate method, but you should be told it is the method before it starts.

If a component is replaced, ask to keep the old one until the repair has proved itself. Nobody reasonable objects. It costs the engineer nothing and it settles any later argument about what was actually changed.

What am I getting in writing, and when?

Ask for the invoice to itemise labour, parts and attendance separately, and for any certification the work requires to be issued at the same time. Agree it before the work, not at the doorstep with a card machine out. A business that issues documents routinely says yes without thinking.

A useful invoice names the component fitted, not just the word repair. If you later sell the property or argue with a manufacturer about a part, that line of text is the whole record. Where work carries its own paperwork, the certificate is not optional and not a favour. Ask when it arrives and by what route.

Two more are worth naming. Ask for a receipt identifying the trading entity, not just a card terminal slip. And if any part of the visit was estimated rather than quoted, ask for that estimate in writing first, even by text. An estimate you can read is not a number you half remember from a phone call.

• Labour, parts and attendance itemised separately on the invoice.
• The actual component named, with make and model where it has one.
• Any certificate the work requires, with a date for when it arrives.
• The trading name and company details of whoever took the money.

Questions that are specific to London housing stock

Ask questions that fit the building you are in, because the building decides most of what goes wrong. London water is hard across the supply area, and hardness is the biggest influence on how hot water components age here, so it belongs in the conversation from the start.

In a Victorian conversion, ask where the stopcock is and whether it is accessible, because a seized or shared one turns a twenty minute repair into an afternoon, and ask how buried pipework will be traced. In a purpose built block with a thermal store such as a Pulsacoil, ask whether the engineer has worked on that unit before, because the controls and the sequence of operation are nothing like a domestic cylinder. In a new build with underfloor heating in screed, ask about access and reinstatement before any cutting.

Ask about scale directly. What did the engineer see on the element, in the heat exchanger or on the coil, and is this failure a one off or the start of a pattern. That answer tells you whether you are buying a repair or deferring a replacement, and you should know which before you spend.

What a vague answer actually means

A vague answer is rarely a lie. It usually means the number has not been decided, and an undecided number gets decided at the point where you have the least leverage, standing in a wet kitchen with the water off. That is the real cost of not asking.

Treat we will see when we get there as a pricing model rather than flexibility, and it depends on the job as an invitation to ask what it depends on. Treat a refusal to quote an attendance charge on the phone as information, and treat pressure to authorise a replacement on the first visit with the caution any rushed decision deserves.

Caution can be overdone, so say the mirror image too. A firm that gives you an attendance charge, an hourly rate and an honest we cannot price the repair until we have seen it is being straight with you. Anyone quoting a fixed repair figure from a phone description is either padding it or planning to revise it. You are not testing for certainty about the total, only for clarity about how the total will be reached.

• A from price with no ceiling and no explanation of what moves it.
• No answer on what happens if the fault cannot be fixed on the day.
• Reluctance to name the qualification or give a registration number.
• Pressure to authorise a full replacement before the fault has been shown to you.
• Cash only, or a refusal to itemise the invoice.
• No clear answer about who is attending or whether they can return.

Where to check the answers you are given

Answers are only worth what you can verify, and most of the verifying happens away from the phone call. Three of the places people look first are genuinely useful, provided you know what each one is actually measuring and what it leaves alone.

Directory badges are the usual shortcut, and they are narrower than they look. Our piece on Checkatrade, Trustatrader and what a directory badge actually means sets out what a badge mechanically certifies, which is a smaller claim than most people read into it, and what it never checks at all.

The reviews sitting underneath those badges are a separate question again, which is why we wrote a piece asking are directory reviews trustworthy and looking at how the ones you end up reading got in front of you rather than at what they say.

Most people start on the map rather than on a directory, so how to read a Google Maps listing for a plumber goes through which parts of a listing carry real information, which parts are bought, and which parts a business writes about itself.

Two questions to ask yourself before you call anybody

Decide what you want from the visit, and gather what the engineer will ask for. Those two minutes change the price more than any negotiation on the phone, because they cut the time spent on site working out what you already know.

Be honest about whether you want this fixed for now or fixed for good. Those are different jobs at different costs, and an engineer can serve either once told which. A fifteen year old cylinder with a failed element can have the element changed, which is sensible if you are selling next spring and a poor decision if you are staying ten years.

Then have the information ready: make and model from the data plate, any fault code noted before it was reset, whether the heating still works, and what changed just before it stopped. A firm with 20 engineers can route the right person to the right job when it knows those things, and cannot when it does not.

• Fixed for now or fixed for good, and say which.
• Make, model and any fault code, photographed rather than described.
• Whether the heating still works, and whether every hot tap is affected.
• What changed immediately before the fault appeared.
• Where the stopcock, the consumer unit and the appliance isolator are.