HIU Maintenance, Service & Repair Across London
Slow hot water and the complaints that follow. Emergency call-outs eating the service charge. No service record when a claim lands. We service, repair and inspect heat interface units across London blocks, and every visit comes back to you as a photographed, per-unit report.
Mainteniq provides planned and bulk heat interface unit servicing, repair and inspection for managing agents, landlords and commercial building owners, and suited to housing associations and build-to-rent operators, across Greater London, all 32 boroughs, from our Westminster SW1 base.
- Pricing is per unit with block rates. Resident access is arranged with the managing agent or concierge, or handled by us directly.
- Every unit receives a photographed service report and certificate through our reporting app, the block receives a compliance pack and a block summary, and contract clients get priority call-outs and an emergency line. Engineers hold SAV Advanced HIU Service Engineer certification.
A heat interface unit (HIU) is the per-flat device in a communal or district heating system.
- It transfers heat from the shared network to each flat's space heating and domestic hot water circuits, replacing the boiler in every home.
- HIUs should be serviced annually; the BESA HIU Technical Standard sets the performance benchmarks and CIBSE CP1 (Heat Networks: Code of Practice) provides the wider operational framework for UK heat networks.
- Strainer cleaning is the single most important maintenance task: a blocked strainer is the leading cause of reduced hot water flow and intermittent heating in London flats.
- A full annual service covers plate heat exchanger descaling, differential pressure valve calibration, mixing valve adjustment, actuator testing and safety checks.
- For landlords and building managers, documented servicing records protect against Fitness for Habitation claims when heating or hot water fails.
The HIU Problems London Blocks Bring Us, and What We Do About Them
Most managing agents do not call about heat interface units until something has gone wrong. These are the six situations we are asked to fix most often, and how a planned programme with proper reporting removes each one.
Residents complain that hot water takes minutes to arrive, or never gets hot
In London's hard water the plate heat exchanger scales up and the strainer blocks. Flow drops, the unit hunts for temperature and the complaints start every autumn.
How we solve it: We descale the plate exchanger, clean the strainers and dirt separator and reset the differential pressure valve. Most units go from minutes to seconds on the same visit, and the before and after readings are in your report.
Emergency call-outs are eating the service charge budget
Valves that seize over summer, actuators that fail on the first cold week, leaks that show up as a ceiling stain in the flat below. Every one is a reactive job at reactive rates.
How we solve it: A planned annual visit finds the seizing valve and the weeping joint before they fail. Contract clients get priority call-outs and an emergency line, so the few real emergencies are handled fast and the rest stop happening.
A complaint or a claim has landed and there is no service record for the flat
Fitness for Habitation claims, deposit disputes and Building Safety Act audits all ask the same question: can you show the heating and hot water were maintained by a competent person?
How we solve it: Every unit we touch gets a photographed, dated report with readings and the engineer's certification, plus a certificate per flat and a block-level compliance pack. It sits in your file before you need it.
The last contractor never finished the block, or finished it and left no reports
Half the flats done, no record of which half, and a spreadsheet nobody trusts. When residents ask whether their unit was serviced, nobody can say.
How we solve it: We quote and schedule the whole block, track every flat as done, no access or follow-up needed, and hand over a block summary at the end. You always know exactly where the programme stands.
Getting an engineer into 60 or 80 flats is a logistics headache
Residents at work, keys held by different people, concierge shifts, and a contractor who turns up once and gives up on the flats they could not reach.
How we solve it: We agree the access plan up front. Either your team or the concierge notifies residents, or we handle the notices and the time slots ourselves. Flats we cannot reach are logged and rebooked in a mop-up visit, not forgotten.
The heat network runs hot and the energy bills show it
Badly set HIUs return water to the network far too hot. The plant works harder, losses climb and the whole block pays for it on the heat tariff.
How we solve it: We calibrate the controls and set the return temperatures correctly on every unit, which improves network efficiency block-wide. Where there is a building management system we integrate the two, so the BMS flags an HIU fault before a resident does.
Every Visit Documented, With Photos, Before You Ask
The difference between a contractor and a maintenance partner is what you hold in your hand afterwards.
Our engineers complete every HIU service in Maintivo, our field service and reporting platform, on site, so the report is photographed, timestamped and sent the moment the job is done. Nothing is written up from memory a week later.
Heat exchanger, strainers, valves and any defect found, so you can see the work without visiting the flat.
Flow and return temperatures, differential pressure and hot water delivery time, recorded before and after.
What was cleaned, calibrated or replaced, and anything that needs budgeting for, with a clear priority.
Who attended, their SAV certification number and the date, for your compliance file.
For the block, one summary
When the programme is complete the managing agent receives a block-level summary alongside the per-unit reports, so the whole scheme can be read on one page:
- Units completed, units with no access and the rebooked date for each
- Faults found across the block, grouped so you can see patterns
- Units recommended for repair or replacement, in priority order
- Next service due date for the whole programme
Reports are yours to keep and forward. They are written so a leaseholder, an auditor or a solicitor can read them, not just an engineer. Every job we do, across every service, is logged the same way, so your block's history is searchable rather than buried in email.
HIU/CIU Specialists for London Properties
We service heat interface units across residential blocks, build-to-rent developments and housing association properties across Greater London. Central London communal heating schemes are the core of our work.
Managing Agents
One contractor for the whole block, one report pack for the file, and fewer resident emails about hot water.
Block & Facilities Managers
A planned programme that stops HIU faults becoming winter emergencies, with a live view of which flats are done.
Housing Associations & BTR Operators
Per-unit records and block summaries that stand up when a complaint, an audit or a Fitness for Habitation claim lands.
Landlords
A single flat on a communal network, serviced properly and documented, so a tenant without hot water is never your problem for long.
Pimlico, Nine Elms, Canary Wharf, King's Cross, Stratford
Every HIU in the block serviced before the heating season
One programme for the whole building: access coordinated with residents, every unit photographed and reported, and a block summary the directors can approve. Blocks on a programme get priority on the same-day line.
Block maintenance contracts for managing agentsWhat is an HIU or CIU?
Heat Interface Units (HIUs) connect your property to a communal or district heating system, delivering heating and hot water without the need for an individual gas supply. Cooling Interface Units (CIUs) are their cooling counterpart, connecting the flat to a communal chilled-water supply.
Where They're Found
How They Work
Why Maintenance Matters
HIU Inspection in London
We carry out HIU inspections across London blocks and estates: a documented check of each heat interface unit's plate heat exchanger, control valves, strainers, flow and return temperatures and differential pressure, with a photographed report for the landlord or managing agent.
An inspection is the right call when residents report slow or lukewarm hot water, when a unit is noisy or leaking, at the handover of a new tenancy, and as the annual health check that keeps a communal heating network compliant and efficient.
- Because most faults sit in the heat exchanger or the controls rather than the network itself, an inspection usually pinpoints the problem in one visit, and if the unit needs a full clean we move straight to a service on the same appointment.
HIU Maintenance Contractors in London
Mainteniq provides HIU maintenance contractors across London for residential blocks, estates and build-to-rent developments, servicing heat interface units on a planned schedule so hot water and heating stay reliable all winter.
Our engineers hold SAV Advanced HIU Service Engineer certification and work on the units most common in London communal heating schemes, including SAV, Danfoss, Caleffi, vTherme and Evinox.
- For a block we agree a visit programme per unit, typically annual, as part of a block maintenance contract, with six-monthly visits for high-occupancy or older systems, and we run it inside one planned maintenance contract with a single point of contact, block-wide reporting and an emergency line for contract clients.
- Where the block also has a building management system we integrate the two, so the BMS flags an HIU fault before a resident does.
What every block receives:
- A photographed service report for every unit, with before and after readings, delivered through our reporting app
- A service certificate per unit and a block-level compliance pack for the managing agent's file
- An access plan agreed up front: your team or the concierge notifies residents, or we handle the notices and time slots ourselves
- Per-unit pricing with block rates, quoted once we know the unit model and count
- A block summary at the end of the programme, plus priority call-outs and an emergency line for contract clients
HIU Service: What a Full Service Includes
An HIU service is a full clean, test and calibration of the heat interface unit: flushing and descaling the plate heat exchanger, cleaning the strainers and filters, testing the hot water and heating control valves, verifying flow and return temperatures and differential pressure, checking for leaks and recording every result.
Most units need this once a year; heavy-use or older units benefit from every six months.
- A serviced HIU delivers hot water in seconds rather than minutes and runs up to 15 percent more efficiently, which is why an annual service costs a fraction of the emergency call-outs it prevents.
- Pricing is per unit with block rates, quoted after we know the model and the number of units.
- If you are unsure how often yours is due, read our guide on how often an HIU should be serviced.
What You Get From Professional Servicing
Measurable improvements residents notice the same day, and a record you can show anyone who asks.
Faster Hot Water
Hot water in under 10 seconds instead of minutes of waiting
Lower Energy Bills
Up to 15% efficiency improvement from a clean heat exchanger and correct return temperatures
Quieter Operation
No more banging, gurgling or whistling sounds
Proof in Your File
12-month service guarantee, photographed report and certificate for every unit
Signs Your HIU/CIU Needs Service
Recognise these common symptoms? They are usually fixed on a single service visit.
Hot water takes too long
Likely cause: Strainer clog or scale buildup on the heat exchanger
Solution: Strainer cleaning and plate descaling
Temperature fluctuates
Likely cause: Mixing valve needs calibration or the actuator is failing
Solution: Valve calibration and actuator testing
Strange noises from the unit
Likely cause: Air in the system or a differential pressure imbalance
Solution: Air bleeding and pressure valve adjustment
Heating not responding
Likely cause: Control failure or a seized valve
Solution: Control verification and valve servicing
Danfoss, SAV, Evinox, Caleffi, vTherme
Fixed on the first visit, with the report in your inbox the same day
Engineers carry the common plate heat exchangers, actuators and strainers for the HIU brands fitted across London, so most faults are cleared in one visit and every job ends with a photographed report through our app.
Our HIU/CIU Service Process
A full service takes around 90 minutes per unit and covers every critical component. The report is completed in the flat, before the engineer leaves.
Inspection & Diagnostics
Cleaning & Descaling
Valve & Control Service
Safety & Compliance
Results You Can Expect
Typical improvements after professional HIU/CIU servicing.
Full pressure and stable temperature
Clean plates and calibrated controls
Lower return temps and reduced cycling
Fewer urgent disruptions and costs
Planned Service vs Emergency Replacement
An annual service per unit is a small, predictable line in the service charge. An emergency replacement is none of those things.
Planned Annual Service
Fixed per-unit price at block rates, quoted in advance and budgeted for once a year.
- Full descaling and cleaning
- Valve servicing and calibration
- Safety and compliance check
- Photographed report and certificate
- 12-month warranty on the work
- Faults caught while they are still small repairs
Emergency Replacement
Unbudgeted, unscheduled and usually in the coldest week of the year, when every contractor is busy.
- New HIU or CIU unit, many times the cost of a service
- Emergency labour at emergency rates
- Days without heating or hot water for the resident
- Possible water damage to the flat below
- Compensation claims and rent reductions
- The same unit could usually have been saved
UK Safety & Compliance
HIU/CIU maintenance is part of a landlord's legal duty to provide heating and hot water. The record of it is what protects you.
Building Safety Act 2022
Accountable persons must be able to show that building systems are maintained and safe. A dated, photographed HIU service record per flat is exactly the evidence an audit asks for.
Fitness for Habitation
Properties must provide adequate heating and hot water. A failed HIU can make a flat legally unfit, leading to rent reductions and claims. Planned servicing, documented, is the defence.
How a Block Programme Runs With Mainteniq
From first message to final report, this is what a managing agent can expect. No chasing, no guessing which flats are done.
Send us the block
Unit count, make and model if you know it, and the address. A photo of one unit's data plate is enough if you do not.
Fixed per-unit quote
Block rates for the whole programme, with servicing, repair and reporting all itemised. No surprises on the invoice.
Access plan agreed
Your team or the concierge notifies residents, or we send the notices and book the slots. Either way, it is decided before day one.
Servicing, tracked flat by flat
Around 90 minutes per unit. Each flat is marked done, no access or follow-up needed, so you can see progress as it happens.
Reports in your inbox
Per-unit photographed reports and certificates through our app, then a block summary with faults, recommendations and next due date.
Stop the Hot Water Complaints Before Winter
Send us the block and the unit count. You get a fixed per-unit quote, an access plan, and a photographed report for every flat when the work is done.
Managing a block or portfolio? Fold HIU servicing into a single planned maintenance contract covering every communal system on one schedule.