What is Rare Plumbing Website?

A bespoke digital atelier providing precision engineering and climate control services for London's most discerning luxury estates.

What causes underfloor heating cold spots?

Cold spots have six main causes: (1) magnetite/sludge settled in lower pipe loops blocking flow, (2) air locks in specific circuits, (3) imbalanced flow rates at the manifold — one circuit starving another, (4) failed thermoelectric actuator stuck in the closed position, (5) blending valve delivering incorrect flow temperature to affected zone, or (6) inadequate floor insulation allowing heat to conduct downward instead of upward. We diagnose with thermal imaging cameras and flow meter readings — no floor lifting required in most cases.

Can you repair underfloor heating without lifting the floor?

In most cases, yes. The majority of UFH faults — actuator failures, manifold blockages, controller wiring issues, pump and blending valve faults — are in accessible components at the manifold. Pipework faults within the screed are rare but would require localised floor lifting. We use thermal imaging to pinpoint the exact location, minimising the area of floor that needs to be disturbed.

My whole underfloor heating system has stopped working — what should I check first?

Check these in order: (1) Is the boiler firing normally? (2) Are any manifold isolation valves closed? (3) Is the UFH pump running — it should feel warm and vibrate slightly? (4) Is the blending valve set to the correct temperature (35–45°C)? If all these check out, call a UFH specialist — the fault is likely in the control wiring or a failed component at the manifold.

Can underfloor heating pipes leak without being visible?

Yes. UFH pipes buried in screed can develop micro-leaks at joints. These are identified by pressure-testing each manifold circuit individually — the leaking circuit loses pressure while others hold. We then use thermal imaging to locate the leak point beneath the floor, allowing a targeted, minimal-disruption repair rather than lifting the entire floor.

How long does UFH fault diagnosis take?

An experienced UFH engineer can typically diagnose the fault within 30–45 minutes. Simple repairs — actuator replacement, thermostat recalibration, air bleeding — are completed in the same visit. More complex issues (concealed leaks, severe sludge contamination) may require a second visit with specialist equipment.

How long should underfloor heating take to warm up?

A screeded wet UFH system typically takes 2–4 hours to reach comfortable temperature from cold. Low-profile overlay systems respond faster — 30–60 minutes. Suspended timber systems with aluminium diffuser plates also respond in 30–60 minutes. If your floor takes significantly longer than these times, the system has a fault — typically inadequate flow, air in the circuit, or a blending valve issue.

Can underfloor heating be flushed like a radiator system?

Yes — underfloor circuits should be flushed periodically, though the process requires care. UFH pipework has a narrower bore (16–20mm) than radiator pipework, so high-pressure flushing must use controlled flow rates to avoid damaging joints. We use a portable flushing pump connected at the manifold, flushing each circuit individually. This is included in our annual UFH maintenance visits.

Do you offer annual maintenance for UFH systems?

Yes — our annual UFH maintenance visit includes: manifold inspection and flow balancing, actuator operation test, water quality analysis (pH, inhibitor, TDS), inhibitor top-up if required, blending valve check and calibration, thermostat/smart control firmware update, and full written report. Annual maintenance is included in our PPM membership plans from £750/year.

020 7458 4949

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RARE Plumbing London engineer diagnosing an underfloor heating manifold fault with thermal imaging

UFH Fault Diagnosis Specialists

Underfloor Heating Repairs London — Cold Spots, Manifold Faults & Leak Detection

Faulty underfloor heating? We find and fix cold spots, manifold faults, leaks and balancing issues — without lifting your floors. Thermal imaging diagnosis by Heatmiser-certified engineers.

020 7458 4949 Book a Repair Visit

Gas Safe Registered

Available 7 Days

4.7★ Rated

13+ Years Experience

Book a Repair Visit

Available 7 days. Thermal imaging diagnosis included.

Transparent Pricing

Clear rates — no call-out fee, no surprises

We charge a straightforward hourly rate with no separate charge for attending. The clock starts when the engineer arrives — not before. Any parts needed are quoted transparently before work begins, so you'll always know the cost upfront.

£150/hr + VAT

No call-out fee · Minimum 1 hour

Standard rate (Mon–Fri, 8am–6pm)£150/hr + VAT

Out-of-hours (evenings & weekends)£195/hr + VAT

Bank holidays (incl. Christmas)£275/hr + VAT

Replacement partsQuoted before work begins

No charge for attending — you only pay for time on site

Fixed quote before any parts are fitted

RARE members save 10% on standard rates

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London's UFH Repair Specialists

Diagnosis from the physics of the system

Most underfloor heating faults we see were caused at installation — pipes spaced too far apart, too little floor insulation, systems never properly balanced, or filled with London's untreated hard water.

RARE's engineers diagnose every fault from the physics of the system. We measure flow rates before claiming a manifold is balanced. We use thermal imaging to find cold spots without lifting floors. We test water chemistry to identify corrosion and scale. This is why our diagnostic visits find the root cause — not just the nearest replaceable component.

Cold spot diagnosis without lifting floors

Manifold repairs & full servicing

Balancing circuits so every room heats evenly

Sludge & debris flushing

Heatmiser NeoHub fault diagnosis & repair

Pump & blending valve replacement

Concealed leak detection via thermal imaging

If at a manifold joint: fitting replacement. If in screed: localised floor lifting at the identified leak point, pipe repair, re-pressurisation and re-screed.

Can't find your symptom here?

Call our engineers on 020 7458 4949 — we'll diagnose your UFH fault over the phone before arranging a visit.

What our clients say

4.7★ across 120+ verified reviews

"Had persistent cold spots for two years. Two other companies replaced actuators without success. RARE did a thermal camera scan, found a partial magnetite blockage in the north circuit, flushed it and rebalanced. Fixed in one visit."

Fiona M.

Holland Park, W11

"Our UFH manifold was leaking and two engineers couldn't find the source. RARE pressure-tested each circuit individually, found the weeping fitting and replaced it without lifting any floor. Professional and methodical."

Alex C.

Belgravia, SW1

"Underfloor heating stopped working entirely on a Saturday. RARE came out the same day — turned out to be a failed circulation pump at the manifold. Replaced and commissioned within two hours. Excellent service."

James W.

Hampstead, NW3

You May Also Need

Underfloor Heating Installation

New wet UFH systems — heat loss calculations, screed and low-profile overlay installs.

Heatmiser Smart Controls

Heatmiser NeoHub fault diagnosis, repair and replacement.

Power Flushing

Remove magnetite from UFH circuits and restore even heat distribution.

PPM Membership

Include your UFH manifold in an annual care plan from £750/year.

FAQ

UFH Repair Questions Answered

Our engineers answer these questions every day. Still not sure? Call us and speak to an engineer directly.

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Property Care Membership

Prefer proactive care? RARE members receive planned servicing, detailed property records and priority access when problems arise. Explore Property Care Membership for professionally managed plumbing and heating maintenance.

Arrange a Property Health Assessment Compare Memberships

Authoritative Sources & References

Wikipedia
Central heating — Wikipedia
Wikipedia — Encyclopaedic overview of central heating systems, heat generation, circulation methods and the history of whole-building heating.
Wikipedia
Boiler — Wikipedia
Wikipedia — Reference on the design and operation of closed-vessel boilers used for central heating and hot water generation.