Caleffi HIU — internals and insulated cover, including pump and expansion vessel.
Compact apartment HIU — as installed, and with the cover off for servicing.
Worcester Bosch HIU as it appears once the cover is fitted.
Real call-outs
Questions from jobs like this
These come from real call-outs. See the full FAQs for boiler, heating, HIU and booking questions.
What's involved in repairing a Heat Interface Unit (HIU)?
HIU faults are usually specific components — a valve, pump, or control board — rather than the whole unit needing replacement. We're accredited on Danfoss and SAV systems, so we can diagnose and fit like-for-like parts without needing a full unit swap in most cases.
My heating works but my hot water doesn't (or vice versa) — what's wrong?
This usually points to a specific component rather than the whole boiler — commonly a diverter valve, flow sensor, or in system boilers, the cylinder's own controls. We isolate exactly which part is at fault before quoting, so you're not paying to replace things that don't need it.
Will I get a fixed price before any work starts?
Yes. Once we've diagnosed the fault, we give you a fixed price for the repair before doing any further work — not an estimate that changes once the job's underway. If we find something unexpected once we're inside the system, we'll always explain it and get your agreement before proceeding.
How quickly can you get to an emergency call-out?
We prioritise no-heat and no-hot-water emergencies, especially for vulnerable occupants or during cold snaps. Call or WhatsApp us and we'll give you a realistic time window rather than a vague "sometime today."
Trustindex verifies that the original source of the review is Google.
Found on checkatrade, first to respond and very swift and quick. Professional simple easy, fast well done. What had to be fixed was fixed no complications pure professionalism
Posted on Google
Asheet PATEL
Trustindex verifies that the original source of the review is Google.
A professional service provided by Richard to resolve under floor heating issue. Will use again and again for other related issuses in the future.
Posted on Google
john vischer
Trustindex verifies that the original source of the review is Google.
Richard was very quick to respond and offered helpful suggestions and was accommodating. He diagnosed the problem quickly and our boiler is working again.
Posted on Google
Brendan McElhill
Trustindex verifies that the original source of the review is Google.
I had a really great experience with Richard at Talis when he repaired my hot water cylinder today in Egham. From the start, he was courteous, friendly, and very quick to respond to my enquiry. He arrived promptly, completed the job efficiently, and clearly knew what he was doing. Everything was handled smoothly and with minimal disruption. The pricing was very reasonable and fair, which was a pleasant surprise. Overall, I’m extremely happy with the service and wouldn’t hesitate to use him again or recommend him to others. 5 Stars
Posted on Google
Siavash
Trustindex verifies that the original source of the review is Google.
Richard was great, punctual and fixed the issue with the first visit. Had all the tools and kept everything clean and tidy.
Posted on Google
Jerome Pellaud
Trustindex verifies that the original source of the review is Google.
Richard Sammon from Talis Heating Solutions came within 60’ to fix in urgency my water pump which burnt out. Based on the picture I sent he found a replacement pump, even though it was already 07:30pm and fixed the issue in an hour. He saved the day!! Highly recommend.
Posted on Google
Henrietta Fforde-Lutter
Trustindex verifies that the original source of the review is Google.
Great, quick service when our boiler wasn't switching to heating mode , and a call out fee that was reasonable considering the distance (Middlesex to near Reading!)
Posted on Google
Miranda Felton
Trustindex verifies that the original source of the review is Google.
Very professional and came to sort our problem out on same day that I called. Very quick response when I phoned and gave an estimated time of arrival.
Many thanks for your help.
Checkatrade reviews
Excellent
Rated 9.96/10
Based on 390 reviews
CCheckatrade customer
Rated 10 out of 10
Above and beyond
Richard was 10/10. He kept contact throughout the whole process, pre-called me 20 minutes before arriving. Once he arrived he assessed the situation with my radiators. Richard took his time to analyse and find the issue. He explained step-by-step what the problem was. He managed to fix my radiators in the extension, that haven’t been working for over the past two years. I can’t recommend Richard enough for his hard work, commitment and knowledge. He was fantastic.
VVerified customer
Rated 10 out of 10Verified by Checkatrade
Great workmanship, very reliable and a job well done.
Richard, is so thoughtful and accomodating, fitting my ceiling leek into his very busy schedule. Giving me precise updates of arrival. His work is totally professional, he is courtious, polite and very precise in his work.
QQ S
Rated 10 out of 10Verified by Checkatrade
Annual gas safety check
Very professional, clear communication, arriving exactly at the agreed time, polite and reliable.
VVerified customer
Rated 10 out of 10Verified by Checkatrade
Very helpful
Richard at Talis was incredibly helpful and very responsive via WhatsApp. We had a message exchange pre 7am where I sent photos of my boiler, and he explained how to resolve my issue myself which meant I didn’t need to wait for him to come out to do a 1 minute job. If I ever have an issue again Richard will be my first go to!
VVerified customer
Rated 10 out of 10Verified by Checkatrade
Hot water system fixed
Richard helpfully diagnosed the problem with our hot water system over the phone and offered a fixed price to fix it. Excellent service experience. Thanks!
VVerified customer
Rated 10 out of 10Verified by Checkatrade
Prompt speedy service
Very satisfied with work, a really great service very professional, I’d recommend them
VVerified customer
Rated 10 out of 10Verified by Checkatrade
Boiler/Thermostat
Did a great job, fixing a new thermostat for the boiler. Arrived as promised and completed the job within an hour. Cleaned up after he finished. Very polite and the charge matched the quote. Highly recommend his work
VVerified customer
Rated 10 out of 10Verified by Checkatrade
Great service
Richard from Talis Heating responded out of hours within half an hour he was at property to correct a valve and reinstate hot water. Really professional and I would recommend him. Amazing service!
VVerified customer
Rated 10 out of 10Verified by Checkatrade
Satisfied Customers
Richard completed a full strip down Boiler Service today. We are happy with the work carried out.
CCheckatrade customer
Rated 10 out of 10
Great service
Great communication - quick issue resolution
VVerified customer
Rated 10 out of 10Verified by Checkatrade
Boiler Service
We just moved into a new house with an old boiler system. It had not been serviced in years.
We booked through Checkatrade, and the earliest date available was Thursday.
Richard called and serviced the boiler on Tuesday.
He also reassured us that it was in good and safe order and helped familiarise us with the operation of it.
I wholeheartedly recommend Talis Heating
VVerified customer
Rated 10 out of 10Verified by Checkatrade
Good service
Pleased with the work carried out by Richard and Kenny. We are now having them do further repairs for us.
What We Do
Services
BOILER INSTALLATION
New boiler, done properly.
10-YEAR WARRANTYGAS SAFE REGISTERED
We supply and install Worcester Bosch and Vaillant boilers for homes and businesses across London and Surrey. Up to 10 year warranty. Fixed price quotes. No surprises.
Legally required for every rental property, every year. We carry out gas safety inspections across London and Surrey and issue your certificate on the same visit.
Talis install, service and repair air conditioning and heat pump systems across London and Surrey — domestic and commercial. F-Gas certified engineers.
Our HIU service includes inspection of the unit and connections, pressure checks, cleaning strainers and filters, heat exchanger performance testing, hot water temperature and flow checks, controls and sensor testing, leak inspection and a service report.
We work with residents, landlords, property managers and housing associations, including planned maintenance programmes for multiple units.
