AI Named the Plumber. Neither Engine Pointed to the Gas Safe Register.

Last Updated on October 5, 2026

Anyone who works on gas in the UK must be on the Gas Safe Register. We asked two AI engines for a trustworthy plumber in 12 cities and checked whether they ever pointed there.

In the UK, anyone who works on gas must be on the Gas Safe Register. It is a legal requirement, and the register is free to search. Customers asking AI for a plumber mostly need taps, leaks and boilers fixed. So we wanted to know whether the engines point people to the register.

On 26 September 2026 we asked ChatGPT and Google Gemini: “Recommend a trustworthy plumber in [city]”, in 12 UK cities. We logged every business named, then checked Companies House, each firm’s own website and, where we could, the Gas Safe Register.

The finding, in five lines

1. The 24 answers contained 86 mentions, covering 75 different plumbers. The two engines agreed on 11 of them.
2. None of the 24 answers linked to the Gas Safe Register. 13 answers mentioned Gas Safe at all, mostly as general advice.
3. Five times, an engine told the reader that a named firm was Gas Safe registered. Not one of those five claims linked to the register.
4. 47 of the 75 advertise gas or boiler work on their own website. Only 13 of those 47 print a Gas Safe registration number. (One of the 47, Leicester Plumbers, is counted from a website we could not tie to the business. Without it the figures are 12 of 46.)
5. 34 of the 75 (45%) matched an active company registered in or near the city. 24 (32%) had no Companies House match, and four matched only a dissolved company.
6. We could search the Gas Safe Register for only 5 of the 75 before its security check stopped us. Two were found under the name the engine gave. The other 70 are recorded as Unchecked.

01 / What the engines said about Gas Safe

ChatGPT’s two firm-level claims both leaned on a secondary source:

• It said Brennan & Son in Southampton had “Gas Safe registration listed publicly”, citing Yell.
• It said Which? Trusted Traders described HeatGlow Heating & Plumbing in Cardiff as “gas-safe registered”.

Gemini’s three firm-level claims (2nd City Gas Plumbing & Heating in Birmingham, Phil Humberstone in Nottingham, SMC Plumbing and Heating in Cardiff) came with no link. The Cardiff answer named MyBuilder and Which? as platforms.

We could check one of the five before the register blocked us. SMC Plumbing and Heating is on the register (registration 570503, registered in Caerphilly). The email domain on the register entry matches the firm’s own website. The other four could not be checked, because the register’s security check stopped our searches (see Limits).

02 / Where the engines’ confidence came from

ChatGPT cited Which? Trusted Traders against 7 of its 52 mentions, TrustATrader against 2, Checkatrade against 2 and Yell against 1. Gemini linked no sources. In four places it named Checkatrade in its text.

The star ratings came almost entirely from map widgets and place cards, or from review counts the engine quoted. Of the 75 ratings shown, the median was 4.9 and the lowest was 4.4. None of those systems is a gas safety register.

03 / The register check

The 34 in the finding are the 32 Active plus the two with a strike-off proposal.

The first business named in 11 of the 24 answers matched an active local company. The first business named in the other 13 did not.

We also searched the Gas Safe Register by the name each engine gave. The register’s security check stopped us twice, so only five firms were searched. Five is too few for a rate, so we show every result.

The two not found do not advertise gas work on their own sites, so they may not need to be registered.

Worked examples

Every example below was logged in this run. None of them is a verdict on the firm’s work.

• Dissolved: Gaswise UK, Nottingham. Gemini: “family-run, 24/7”, with accredited boiler installers. GASWISE (UK) LIMITED (07896319) was dissolved on 14 August 2018. The firm’s own site prints Gas Safe number 190680 and no company number.
• Dissolved: Leicester Plumbers. Gemini’s first pick in Leicester (4.9), also named by ChatGPT (“4.9/5 from 377 reviews”). LEICESTER PLUMBERS LTD (13611442) was dissolved on 16 August 2022. Two different websites use the name, so we cannot tell which business the engines meant.
• Dissolved: County Plumbers, Brighton. ChatGPT (“5.0/5 from 133 reviews, 24/7”). The local COUNTY PLUMBERS LTD (12614834, BN10) was dissolved on 2 January 2024. The firm’s website footer still says “County Plumbers Ltd”.
• Name elsewhere: John The Plumber, Leeds. ChatGPT’s first pick in Leeds (4.9, 393 reviews). Its own site says “Gas Safe registered” but prints no number. A register search on that name returned one business, in Somerset. The Leeds firm may be registered under another name, but a customer searching the name the engine gave would find only the Somerset business.
• Not a plumber: Newcastle Heating and Plumbing – Cowgate. ChatGPT named it second in Newcastle (“4.8/5 from 233 reviews”). Its own website shows it is a trade counter selling parts, not an installer.
• Advert: “Gas & Plumbing Services Leeds | Boiler Repair Services | Emergency Plumber Leeds”. Gemini showed this string, taken from a map listing, as a business name, with a 5.0 card and a line about “complex gas systems”. We found no website and no company of that name.
• No website: Brighton Plumbing Done Right. ChatGPT (“5.0/5 from 76 reviews”). The web address we found shows only a dashboard for managing a Google Business listing, with no business content. There is no company of that name on the register.
• Renamed: Zodiac Plumbing & Heating, Manchester. The name ChatGPT used is the company’s former name. It now trades as ZODIAC PLUMBING & HEATING SOLUTIONS LTD, registered in Wilmslow.
• Different name: AB Plumbing & Heating, Birmingham. The only same-name company is registered in Surrey. The firm’s own site prints 09680455, A BAILEY PLUMBING & HEATING LTD in Kings Norton, which matches the Which? listing that ChatGPT cited.
• Correctly drawn line: Jack The Plumber, Birmingham. Gemini said this firm “does not handle gas boiler repairs”, and its website agrees. Not every plumber needs to be on the Gas Safe Register, only those who do gas work.

The evidence, in screenshots

These are the register entries behind the worked examples and the Gas Safe table above, captured on 26 September 2026. We have cropped out our own account details and redacted street addresses, phone numbers and email addresses.

Same question, asked again

At 20:08 the same evening we asked ChatGPT the Leeds question again, in a fresh temporary chat. John The Plumber was still its first pick. It told the reader to verify an engineer’s Gas Safe registration, and said one firm is Gas Safe registered, but again it gave no link to the register. Its links went to Which? Trusted Traders and TrustMark. This follow-up is not part of the counted sample.

What this means for a UK plumber (no budget required)

Structure before scale. If you do gas work, the registration number is the single most useful line on your website, and 34 of the 47 firms advertising gas or boiler work did not print one.

• Print your Gas Safe number as text, not only as a logo. A logo proves nothing to a customer or a machine. The number can be checked in seconds.
• Use the trading name that appears on the register. If your Gas Safe entry, your company and your Google listing use three different names, nothing can join them up.
• If you do not do gas, say so. Jack The Plumber’s site says it plainly, and Gemini repeated it accurately.
• Tidy dead company names. If a company was dissolved, update the footer, the Google profile and the directories.

See how AI describes your business with the free Whito Visibility Check: https://whito.co.uk/visibility-check/. List your business free: https://whito.co.uk/list-your-business/.

Register-backed, not review-backed.

Method in brief

• Question. “Recommend a trustworthy plumber in [city]”, asked once per engine in each of 12 cities: Leeds, Manchester, Birmingham, Bristol, Sheffield, Nottingham, Leicester, Coventry, Newcastle, Cardiff, Southampton and Brighton. Collected on 26 September 2026 between 16:33 and 16:55 UK time.
• Engines. ChatGPT in a temporary chat on the default model, and Google Gemini on the free default model (shown as Flash-Lite). We used the consumer websites, with a new chat for each question.
• Companies House. Searched as for our locksmith study: the name as written plus one generic-words-removed variant. A same-name company in the same area counts as a match. A same-name company only elsewhere, or two candidates, counts as Ambiguous.
• Websites. Each firm’s own site was checked for a street address, a company number, a Gas Safe number, and whether it advertises gas or boiler work.
• Gas Safe Register. We searched the public register by trading name exactly as the engine wrote it, with one legal-name variant where the firm’s site shows Ltd or Limited. On 26 September 2026 the register’s website put up a human-verification check after our first search, and again after four more. We do not complete those checks, so five firms were searched. The other 70 are recorded as Unchecked, and no rate on this page depends on them. If the full pass is completed, this page will be updated and dated.
• Screenshots. Register entries for the worked examples were captured on 26 September 2026, after the counts were made. The ChatGPT follow-ups were asked separately that evening and are not in the counts.

Limits

• “Trustworthy” is our prompt, not our verdict. Whito has not assessed any firm’s work.
• Gas Safe applies to gas work only. A plumber who never touches gas does not need to be registered. Missing from the register is only a concern for firms that do gas work.
• Not being on Companies House proves nothing. Sole traders do not register there. A No match does not mean the plumber is fake or unsafe.
• The Gas Safe pass is incomplete. Only five firms were searched before the register’s security check blocked us. The other 70 are Unchecked. A name not found on the register can mean the firm is registered under a different name.
• The website data has gaps. Our checker read summaries of each site, so a number printed only in an image or a script-loaded footer could be missed. Four sites would not open, and two names matched more than one site.
• One run, one day. This was one run per engine per city, from signed-in accounts. Gemini has no temporary mode.

Corrections and right of reply

If you run one of the businesses named and something is wrong, email hello@whito.co.uk. Our corrections policy is at https://whito.co.uk/corrections/.

Cite this research

Whito Research (2026). AI named the plumber. Neither engine pointed to the Gas Safe Register. Whito, 26 September 2026. https://whito.co.uk/plumbers/research/ai-plumbers-gas-safe-register-check/. Key finding: none of 24 AI answers linked the Gas Safe Register, and 34 of 75 plumbers named (45%) matched an active local company.

Common questions

What did we ask?

“Recommend a trustworthy plumber in [city]”, once each on ChatGPT and Google Gemini in 12 UK cities, on 26 September 2026, using the ordinary consumer chat sites on their default models.

How did we check?

We checked Companies House by name and area, and each firm’s own website for an address, a company number, a Gas Safe number and any gas work advertised. We searched the Gas Safe Register for five firms before its security check stopped us.

Does this mean the firm is unsafe?

No. Only plumbers who do gas work must be on the Gas Safe Register, and a firm can be registered under a different name from the one an AI engine gave. Always ask to see the engineer’s Gas Safe ID card before gas work.

Can I quote these numbers?

Yes, free, with a link to this page and the collection date, 26 September 2026.

Related Whito research

• Google AI plumber recommendations study
• Will AI recommend your plumbing business?
• How accurate are AI business recommendations?
• We asked AI for a locksmith. Then we checked Companies House
• How to check a plumber is Gas Safe registered
• Plumbers hub · All research · Whito Data

Whito

Whito is an independent UK research publisher. We publish research on how UK businesses are found, trusted and priced: what they cost to market, how their sectors work, and who actually gets recommended. Studies are free to read, every figure carries the date it was checked, and nobody pays to appear.

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