Boiler Repair Costs UK: Call-Out, Parts & Labour Rates

Quick Answer: A UK boiler repair prices at £70-£120 for the call-out (which typically includes the first 30-60 minutes of diagnostic time), £55-£95/hour for subsequent labour, and £120-£480 for the most common parts. A typical PCB (printed circuit board) replacement runs £280-£420 total, a diverter valve £180-£280, a pump £200-£350, and a fan £200-£320. All gas work must be carried out by a Gas Safe registered engineer per the Gas Safety (Installation and Use) Regulations 1998. The "50% rule" — repair vs replace — kicks in when the repair cost exceeds 50% of the price of a new boiler installation; at that point replacement is usually the better long-term decision.

Summary

Boiler repair is the highest-volume call-out work in UK plumbing — a typical Gas Safe engineer carries out 200-400 repair visits per year, alongside servicing and installation. Pricing has to balance two pressures: customers expect a competitive call-out fee (the "diagnostic" charge they compare against other engineers), and the engineer needs to recover van costs, certification fees (~£200/year Gas Safe + insurance), and the genuine cost of stocking common parts.

The pricing structure used by most successful boiler engineers is: a fixed call-out fee covering the first 30-60 minutes (£70-£120), then a clear hourly rate (£55-£95) for additional time, with parts at cost + 20-40% markup. Some engineers prefer fixed-price common repairs ("PCB replacement £350 fully fitted") — this works well for customer trust but only if the engineer is confident in their diagnostic accuracy and can complete the job in the time priced.

This guide covers call-out structures, fixed-price common repairs, parts pricing for the most common faults, manufacturer-specific error codes, warranty considerations, the 50% repair-vs-replace rule, and the regulatory framework under Gas Safety Regulations 1998 and Boiler Plus 2018. For full boiler installs see boiler installation pricing guide; for service pricing see boiler service pricing guide.

Key Facts

Call-out and labour rates

Common parts — supply and total fitted price

Parts markup and supply

Warranty considerations

Regulatory

Quick Reference Table

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Common Repair Diagnostic Time Parts Cost Labour Time Total Fitted (Regional) Total Fitted (London)
Repressurise system (no fault) 0.5 hr — 0.5 hr £75-£120 £95-£150
Replace pressure relief valve 0.5 hr £25-£55 1 hr £130-£220 £170-£280
Replace expansion vessel (internal) 1 hr £55-£140 1.5 hr £200-£350 £260-£440
Replace expansion vessel (external) 1 hr £65-£140 1.5 hr £220-£380 £280-£480
Replace pressure sensor 0.5 hr £35-£95 0.5 hr £140-£220 £180-£280
Replace NTC sensor 0.5 hr £15-£45 0.5 hr £100-£180 £140-£240
Replace ignition electrode 0.5 hr £18-£45 0.75 hr £120-£200 £160-£260
Replace diverter valve actuator 0.5 hr £45-£95 1 hr £170-£280 £220-£360
Replace diverter valve (full) 1 hr £75-£160 1.5 hr £230-£380 £300-£480
Replace 3-way valve (system boiler) 1 hr £55-£120 1.5 hr £200-£340 £260-£420
Replace pump 1 hr £85-£190 1.5 hr £260-£440 £340-£560
Replace fan assembly 1 hr £95-£190 1.5 hr £260-£420 £340-£540
Replace PCB / main board 1 hr £120-£280 1 hr £300-£480 £400-£620
Replace gas valve 1.5 hr £120-£280 2 hr £380-£600 £480-£760
Replace plate heat exchanger 1.5 hr £85-£180 2 hr £300-£500 £400-£640
Replace primary heat exchanger 2 hr £280-£780 3-4 hr £680-£1,400 £880-£1,800
Replace flue gas seal / collar 0.5 hr £18-£45 1 hr £130-£220 £170-£280

Detailed Guidance

Call-out pricing structures — which works

Three common pricing models, each with trade-offs:

1. Flat call-out + hourly rate (most common)

2. Fixed-price common repairs

3. Diagnostic charge then quote

Most successful independent engineers use hybrid: call-out + first 60 minutes for £85-£110, then fixed-price for common repairs (PCB, diverter, pump, fan) or hourly for unusual jobs.

Standard fault diagnosis workflow

A structured diagnosis approach saves time and shows the customer you're being thorough:

1. Customer interview (5 min) — when did it stop, error
   code, noises, cold radiators, last service
2. Visual inspection (5-10 min) — system pressure (1.0-1.5
   bar cold), filling loop, visible leaks, condensate drain,
   flue terminal, isolators on
3. Read error code (2 min) — cross-reference manufacturer
   codes; codes are starting point, not diagnosis
4. Test sequence (15-30 min) — power cycle, fire in CH and
   DHW, check flow/return temperature ramp, test gas working
   pressure, check combustion with flue gas analyser
5. Component testing — multimeter, manufacturer service
   manual for expected values, confirm fault before quoting

The single biggest cause of customer complaint about boiler repair is misdiagnosis — replacing a £280 PCB when the fault was a £35 pressure sensor. Always verify the fault before quoting the replacement part.

Manufacturer error codes — quick reference by brand

Error codes are starting points, not final diagnoses. The same code can indicate different faults depending on system conditions.

Worcester Bosch (Greenstar 8000, 4000, 30Si, 38CDi, etc.)

Vaillant (ecoTEC Plus, ecoFIT, ecoFIT Pure)

Ideal (Logic, Vogue, Mexico, Independent)

Baxi (Platinum, Duo-tec, EcoBlue, 800 series)

Glow-worm / Vokera

Always verify with the manufacturer's service manual on the job — error code definitions are updated with firmware revisions.

The common faults and what they actually mean

Pressure dropping

No hot water but heating works

No heating but hot water works

Boiler kettling / banging noises

Boiler locks out / no display

The 50% rule — repair vs replace

The decision point: when does repair stop making economic sense?

Replace if:

Repair if:

Marginal (30-50% of new install):

Worked example — 9-year-old Worcester 30CDi combi, primary heat exchanger failed:

Option Cost
Repair (heat exchanger replacement) £880
New boiler installed (mid-range Vaillant ecoTEC) £2,800
Repair as % of new install 31%

Decision: repair is justifiable, but flag to customer that other components (pump, PCB) may follow in 2-4 years. Customer can decide.

Same scenario but PCB also failed:

Option Cost
Repair (heat exchanger + PCB) £1,280
New boiler installed £2,800
Repair as % of new install 46%

Decision: marginal. Replacement makes more sense given two major component failures suggest end-of-life.

Gas safety and Carbon Monoxide

Every boiler repair visit is an opportunity to verify gas safety. The Gas Safe engineer's responsibility extends beyond the boiler: combustion test (CO <100 ppm air-free; CO/CO₂ ratio <0.004), gas working pressure (typically 18-21 mbar natural gas under load), flue inspection (terminal location compliant with Part J), ventilation, and CO alarm presence (mandatory in any room with a fuel-burning appliance per the Smoke and Carbon Monoxide Alarm (England) Regulations 2022).

If any condition is unsafe (immediately dangerous "ID" or at risk "AR"), the Gas Industry Unsafe Situations Procedure (GIUSP) applies: warning notice issued, appliance turned off with permission, gas transporter notified. Never sign off a boiler as safe to use if it's not.

Pricing walkthrough — diverter valve replacement

Customer reports no hot water; heating fine. Sunday afternoon emergency call-out vs weekday equivalent:

Item Sunday OOH Weekday
Call-out + first hour £140 £95
Additional 1.5 hr labour £105 £98
Diverter valve (Worcester) £140 £140
Sundries £15 £15
Subtotal £400 £348
VAT 20% £80 £70
Total £480 £418

Out-of-hours premium ~15-25%. Customer accepts because no hot water on a Sunday is non-negotiable.

Frequently Asked Questions

How much should a boiler engineer charge per hour?

Standard regional rates in 2026 are £55-£95/hour for the time after the call-out fee, with London and South East commanding £75-£120/hour. Premium rates apply out-of-hours (typically 30-50% uplift). The hourly rate must cover: van costs (£8/hour), Gas Safe registration and insurance (£3/hour), training and tool replacement (£2/hour), pension and time off (£8/hour), and the engineer's wage and profit. £55/hour is the realistic minimum to sustain a viable business; below that you're losing money on every job.

Should I offer fixed-price repairs?

Fixed-price repairs work well for the most common faults (PCB, diverter, pump, fan, expansion vessel) where diagnostic time is short and the part is well-known. They build customer trust and remove friction from the buying decision. They don't work for: intermittent faults (often need return visits), system-wide issues (sludge, multiple failures), or premium/rare boilers where parts pricing varies. Hybrid approach is best: fixed prices on the top 8-10 common repairs, hourly for everything else.

How long does a typical boiler repair take?

Most single-component replacements take 60-120 minutes including diagnosis. PCB and diverter valves are typically the longest at 90-150 minutes. Heat exchanger replacement is 3-5 hours. Adding a return visit for parts delivery extends to a 2-visit job — diagnose Day 1, repair Day 2 — common for non-stocked PCBs and gas valves.

What's the most common boiler fault?

Low pressure / pressure dropping is the #1 call-out for combi boilers — typically the expansion vessel diaphragm has failed, or there's a small leak in the system. Diverter valve failure is #2 (no hot water but heating works). PCB failure is #3 but most expensive. Sludge-related kettling is #4 and growing as boilers fitted in 2010-2015 reach the limescale-accumulation age.

Do I need to be Gas Safe registered to work on boilers?

Yes, by law. The Gas Safety (Installation and Use) Regulations 1998 require that all gas work in domestic and commercial premises be carried out by a Gas Safe registered engineer (the successor to CORGI). Even diagnostic work that involves removing covers or testing gas pressure must be by a Gas Safe registered person. Unregistered work is a criminal offence and voids any boiler warranty.

Regulations & Standards