Why is my boiler losing pressure?

Closed hydronic systems should maintain pressure indefinitely — if pressure is dropping, there's a leak somewhere. Common locations: expansion tank with failed diaphragm (waterlogged), pressure relief valve weeping, leak at boiler fitting connections, leak at circulator pump seal, leak in distribution piping (radiator connections, baseboard, radiant floor tubing). We perform a system pressure test with isolation valves to localize the leak.

Why does my boiler short-cycle?

Short-cycling (firing and shutting off rapidly) usually indicates oversized boiler for the heating load, failing controls, or air binding in the system. Diagnostic: verify boiler input vs. calculated heat loss (oversized common on older installs), check aquastat or control settings, verify circulator operation, bleed air from system high points. Mod-con boilers should modulate down rather than cycle off; if a mod-con is short-cycling, the control or modulation system likely needs attention.

How often should I service my boiler?

Annual service is standard and required to maintain most manufacturer warranties. Service should include: combustion analysis, pressure verification, circulator operation check, expansion tank pressure check, water quality assessment, visual inspection of near-boiler piping. Our tune-up service covers boilers at $129 per visit or included with our Comfort Care plan.

Should I switch from steam to hot water?

Major project, rarely cost-justified on residential. Steam-to-hot-water conversion requires replacing the boiler, replacing the radiators (steam radiators are designed for steam supply, not hot water at typical operating temperatures), and modifying the distribution piping. Conversion cost typically $32,000-$58,000 for a 2,500 sq ft home. We recommend keeping steam systems as steam unless major modifications are happening for other reasons.

My boiler is making strange noises — is that a problem?

Depends on the noise. Gentle 'ticking' sounds during heating cycles are normal (metal expanding with temperature). Loud 'banging' or 'knocking' usually indicates: air in the system (bleed required), low water level (auto-fill valve issue), kettling (heat exchanger scale or extreme over-temperature), or steam hammer on steam systems (improper pitch causing water to collect in steam lines). Persistent unusual noise warrants diagnostic service before damage occurs.

Boiler Repair in Salt Lake County

December 28, 2024. 11°F outside, 4:18 a.m. dispatch call. The Yalecrest customer Margaret R. — whose furnace story appears on multiple pages of this site — called us about a second property she manages: a 1908 brick duplex on 1st Avenue she’d inherited from her parents in 2011. Heat was out in both units. Indoor temperature 51°F in the lower unit (tenants away for holidays) and 47°F in the upper unit (her sister visiting). The boiler — a 2008 Burnham Series 2 cast iron sectional, 100 MBH input — would attempt ignition, fire briefly, then shut down with a board lockout code. Eli Tran arrived at 5:32 a.m. and worked through the diagnostic sequence: gas pressure correct, electrical supply correct, draft pressure correct, but the pilot flame was failing to stay lit during the trial-for-ignition window. Pilot generator (thermopile) reading 320 mV under flame — should be 700+ mV. The pilot generator had degraded over 16 years to where it could light the pilot but couldn’t generate enough millivoltage to keep the main valve open. Replacement: Honeywell Q313A pilot generator from truck stock, $185 installed, total visit including the after-hours diagnostic fee $385 (the $149 after-hours fee waived because Margaret is on our Comfort Care plan). System running normally by 6:48 a.m. Both units back to comfortable temperature by 9:00 a.m. This is the entire repair philosophy for hydronic equipment: most failures are small specific components in cheap subsystems. The pilot generator, the circulator pump, the expansion tank, the thermocouple, the control module. Identify the actual failure, replace the specific part, document the work. Don’t sell a $14,000 new boiler when a $185 part will run reliably for another 8-10 years.

Boiler repair is a specialty within HVAC — not every HVAC contractor handles hydronic work and not every “boiler service” contractor handles hot-water hydronic, steam, and modern modulating-condensing equipment with equal competence. Our hydronic specialists carry separate certifications and training paths from our forced-air technicians: factory training through Viessmann, Weil-McLain, U.S. Boiler, Buderus, and Navien; certifications in steam system service (Pollak Process and Specialty Equipment training); experience across the four broad equipment categories (cast iron sectional hot water, cast iron sectional steam, modulating-condensing hot water, and combi units). This page covers our diagnostic approach to boiler failures, the most common failure modes by equipment type, what repairs cost, and when economics tip toward full replacement (covered in detail on the boiler installation page).

Common Failure Modes by Equipment Category

Cast Iron Sectional Hot Water Boilers (1950s-2000s)

Circulator pump failure (~25%):: Bearings wear out, motors burn out, impellers corrode. Common pumps: Taco 007 (most common residential), Grundfos UP15 and UP26 series, Bell & Gossett NRF series, Armstrong Astro. Replacement cost: $385-$640 installed including new pump and isolation valves where needed. ECM pump upgrade ($545-$820) reduces electricity consumption 60-70% and is recommended on pumps running 4,000+ hours per heating season.
Expansion tank waterlogging (~15%):: Older steel expansion tanks lose their air charge over years, eventually waterlogging completely (no compressible air remaining). Symptom: pressure relief valve weeping water, system pressure climbing above normal. Modern diaphragm-type expansion tank replacement: $285-$485 installed.
Pilot generator (thermopile) failure (~12%):: On older equipment with standing pilots. Pilot generator degrades over 12-18 years, eventually unable to produce sufficient millivoltage to hold the main gas valve open. Symptom: equipment lights pilot but main burner won’t fire, or fires briefly then shuts down. Replacement: $145-$245 installed.
Gas valve failure (~10%):: Solenoid coil failure, internal valve sticking from age and contamination, pilot valve issues. Symptom: no gas flow on demand. Replacement: $385-$640 installed (Honeywell V8043, Robertshaw 7000 series, White-Rodgers 36G54).
Boiler sectional gasket leaks (~10%):: Cast iron sectional boilers are assembled from individual cast iron sections sealed with high-temperature gaskets. Gaskets degrade over 30-50 years and develop slow leaks at the joints. Repair: section disassembly, gasket replacement, reassembly. Cost: $640-$1,400. On boilers 40+ years old with multiple gasket leaks, repair costs approach replacement and the economics shift.
Aquastat or controller failure (~8%):: The aquastat controls boiler operation based on water temperature. Honeywell L8148/L8124, Carlin 60200 series, Hydrolevel HydroStat. Replacement: $285-$485 installed.
Low water cutoff failure (~5%):: McDonnell & Miller PSE-802 or 67/65 series. Safety device that shuts down boiler if water level drops. Failures usually present as “boiler won’t start” because the safety circuit isn’t closing. Replacement: $385-$540 installed.
Other (~15%):: Various: thermocouple replacement ($85-$165), gas valve coil replacement only ($245-$385), igniter replacement ($185-$285), pressure relief valve replacement ($145-$245), transformer replacement ($145-$215), thermostatic radiator valve failures ($85-$245 per radiator).

Modulating-Condensing Boilers (2005-Present)

Control module failure (~20%):: The integrated control board manages modulation, sequencing, fault diagnostics. Boards fail from voltage spikes (summer monsoon lightning), internal component aging, water damage from condensate overflow. Symptoms: error codes, lockouts, intermittent operation. Replacement: $640-$1,200 installed (Vitotronic, Sage 2.1, Logamatic, Navien NCB control).
Ignition failure (~18%):: Spark ignition system failures — faulty igniter, faulty flame rod, fouled flame rod from condensate splash. Diagnostic similar to forced-air furnaces (igniter resistance test, flame rod microamp measurement). Repair: $245-$485 typical.
Condensate trap blockage (~15%):: Mod-con boilers produce mildly acidic condensate (pH 3-5) that drains continuously during operation. Drain trap clogged from biological growth or sediment causes condensate to back up into the boiler, triggering safety shutdown. Cleaning: $145-$285. Sometimes points to neutralizer cartridge replacement ($85-$185).
Circulator pump failure (~12%):: Same as cast iron systems — bearings, motors, impellers wear out. Modern boilers typically use ECM pumps with longer service life. Replacement $385-$840 installed.
Heat exchanger fouling (~10%):: Stainless steel or aluminum heat exchanger develops scale or biological deposits on the water side. Symptoms: reduced output, longer cycles, sometimes error codes for low delta-T. Chemical cleaning service: $385-$840. Severe fouling may require heat exchanger replacement ($1,400-$2,800) or boiler replacement on equipment 12+ years old.
Gas valve failure (~8%):: Modulating gas valves (Honeywell VR8204, Maxitrol GV60) used on mod-con units fail from age, contamination, or coil failure. Replacement: $485-$840 installed.
Sensor failure (~8%):: Supply temperature sensor, return temperature sensor, outdoor sensor, flue gas sensor. Boilers use multiple temperature sensors that feed into modulation logic. Failed sensor triggers fault code; equipment may lock out. Replacement: $145-$285 per sensor.
Other (~9%):: Pressure switch failures, transformer failures, blower/inducer failures, fan motor failures (on some platforms), pressure relief valve weeping.

Combi Boilers (Boiler + Tankless DHW)

All the mod-con failure modes above, plus:
DHW heat exchanger failure (~15% of combi-specific failures):: Secondary plate heat exchanger that handles DHW develops mineral scale or pinhole leaks. Symptoms: insufficient DHW temperature, fluctuating temperature during use, leak in the combi unit. Plate heat exchanger replacement: $385-$840 installed.
Flow sensor failure (~10%):: Flow switch detects DHW demand to initiate heating. Failure causes no DHW response when fixtures are opened. Replacement: $185-$285.
Diverter valve failure (~8%):: 3-way valve that routes hot water between space heating and DHW circuits. Internal valve seizes from scale buildup or wear. Replacement: $285-$485.

Steam Boilers (Cast Iron Sectional, Pre-1950 Buildings Common)

Low water cutoff failure (~30%):: Critical safety device on steam systems — failure can be catastrophic if not detected. McDonnell & Miller 67, 750, or PSE-802 series. Annual inspection and biennial replacement strongly recommended on commercial systems.
Boiler water level controller failure (~20%):: Controls makeup water addition to maintain proper water level. Failures cause over-fill (water carryover into steam lines, hammer) or under-fill (low water cutoff trip).
Air vent failures (~15%):: Steam systems need air vents at radiators and main vents to allow air displacement during steam fill. Failed vents cause radiators that don’t heat (air-bound) or steam leakage at vents.
Pressure control failure (~10%):: Honeywell pressuretrol (PA404) controls boiler pressure for steam systems. Replacement: $285-$485.

Our Diagnostic Procedure

Customer conversation. What’s happening, when did it start, any error codes displayed, recent service history. Boilers communicate failures more verbosely than forced-air equipment — the error code (if present) often points directly to the failure mode.
System pressure check. Static pressure on the boiler gauge should read 12-18 psig for residential. Operating pressure should rise to 14-20 psig during high-fire. Pressure significantly above 25-30 psig indicates relief valve weeping or expansion tank failure.
Visual inspection. Boiler exterior, near-boiler piping, electrical connections, condensate drain (mod-con equipment), pilot light status (older equipment), error code display.
Combustion analysis. Testo 320 measurement during steady-state. CO under 100 ppm air-free, O₂ 5-8% (mod-con) or 6-10% (cast iron), CO₂ 9-11%, flue gas temperature appropriate for equipment type.
Gas pressure verification. Manometer at gas valve inlet (7″ WC Dominion supply pressure under operating load) and outlet (altitude-derated manifold pressure per equipment spec).
Electrical measurements. Voltage at boiler terminals during ignition attempt. Pilot generator millivoltage on standing-pilot equipment (target 700+ mV). Igniter resistance on spark-ignition equipment. Flame rod microamp signal during operation.
Circulator pump operation. Pump running during heat demand? Pump amperage compared to nameplate? Pump producing flow (verified by feel of supply piping vs. return piping — significant delta-T indicates good flow)?
Sensor checks (on mod-con equipment). Outdoor sensor reading vs. actual outdoor temperature. Supply and return temperature sensors during operation.
Documentation and customer consultation. All measurements recorded. Findings explained. Written quote provided for the repair scope.
Repair and verification. Repair performed. System cycled through full operation. Final measurements verify proper operation. Documentation completed.

Pricing Reference (Q2 2026)

Diagnostic visit:

$89 weekdays, $149 after-hours. Credited toward authorized repair.

Common cast iron boiler repairs:

Pilot generator/thermopile replacement: $145-$245
Thermocouple replacement: $85-$165
Pilot assembly cleaning/replacement: $185-$285
Gas valve replacement: $385-$640
Circulator pump replacement (standard): $385-$640
Circulator pump upgrade to ECM: $545-$820
Expansion tank replacement: $285-$485
Pressure relief valve replacement: $145-$245
Aquastat replacement: $285-$485
Low water cutoff replacement: $385-$540
Sectional gasket replacement (per joint): $385-$640
Transformer replacement: $145-$215

Common mod-con boiler repairs:

Igniter or flame rod replacement: $245-$485
Condensate trap cleaning: $145-$285
Neutralizer cartridge replacement: $85-$185
Sensor replacement (temperature, outdoor, flue): $145-$285
Modulating gas valve replacement: $485-$840
Control board replacement: $640-$1,200
Heat exchanger chemical cleaning: $385-$840
Plate heat exchanger replacement (combi DHW): $385-$840
Diverter valve replacement: $285-$485
Flow sensor replacement (combi): $185-$285

Common steam boiler repairs:

Low water cutoff replacement: $385-$540
Boiler water level controller replacement: $485-$840
Pressuretrol replacement: $285-$485
Main vent replacement: $145-$285
Radiator air vent replacement (per vent): $45-$95
Steam header repair: $385-$1,200 depending on access

Comfort Care plan discount:

15% off parts and labor for plan members. Plan also waives the $149 after-hours dispatch fee.

Repair vs. Replacement Decision Framework

The same age-and-economics analysis applies to boilers as to forced-air furnaces, with some hydronic-specific considerations:

Under 12 years old, in good condition otherwise:: Repair almost always wins. Modern boilers have long expected service life (15-25 years typical for mod-con, 25-40 years for cast iron); a single component failure doesn’t change that expectation.
12-20 years old:: Depends on component. Major failures (heat exchanger, control module on mod-con) point toward replacement if repair approaches 40% of replacement cost. Minor failures (circulator, expansion tank, gas valve) stay with repair almost always.
20+ years old cast iron, 15+ years old mod-con:: Replacement becomes increasingly viable. Operating efficiency on aging equipment is significantly lower than current platforms; cumulative repair costs over remaining service life often exceed savings from continued repair. Combined with available Dominion Energy ThermWise rebates ($300-$400) and IRA 25C tax credit ($1,200), the math frequently favors replacement.
30+ years old cast iron, 20+ years old mod-con:: Replacement almost always wins. Continued operation creates compounding risk — one major failure during a winter cold snap creates emergency replacement scenarios at premium pricing. Plan replacement proactively.
Special case: historic radiator preservation.: If your home has original cast iron radiators that you value, boiler replacement preserves them entirely. The radiator distribution system continues to serve the house; only the heat source changes. See the boiler installation page for retrofit scenarios.

Frequently Asked Questions

Why is my boiler losing pressure?: Closed hydronic systems should maintain pressure indefinitely — if pressure is dropping, there’s a leak somewhere. Common locations: expansion tank with failed diaphragm (waterlogged), pressure relief valve weeping, leak at boiler fitting connections, leak at circulator pump seal, leak in distribution piping (radiator connections, baseboard, radiant floor tubing). We perform a system pressure test with isolation valves to localize the leak. Repair scope depends on leak location.
Why does my boiler short-cycle?: Short-cycling (firing and shutting off rapidly) usually indicates oversized boiler for the heating load, failing controls, or air binding in the system. Diagnostic: verify boiler input vs. calculated heat loss (oversized common on older installs), check aquastat or control settings, verify circulator operation, bleed air from system high points. Mod-con boilers should modulate down rather than cycle off; if a mod-con is short-cycling, the control or modulation system likely needs attention.
How often should I service my boiler?: Annual service is standard and required to maintain most manufacturer warranties. Service should include: combustion analysis, pressure verification, circulator operation check, expansion tank pressure check, water quality assessment, visual inspection of near-boiler piping. The fall furnace tune-up framework on the furnace tune-up page covers similar scope for hydronic equipment at $129 per visit or included with our Comfort Care plan.
Should I switch from steam to hot water?: Major project, rarely cost-justified on residential. Steam-to-hot-water conversion requires replacing the boiler, replacing the radiators (steam radiators are designed for steam supply, not hot water at typical operating temperatures), and modifying the distribution piping (steam systems use single-pipe or two-pipe configurations that don’t translate directly to hot water). Conversion cost typically $32,000-$58,000 for a 2,500 sq ft home. We recommend keeping steam systems as steam unless major modifications are happening for other reasons (full gut renovation, addition requiring new heating zone).
My boiler is making strange noises — is that a problem?: Depends on the noise. Gentle “ticking” sounds during heating cycles are normal (metal expanding with temperature). Loud “banging” or “knocking” usually indicates: air in the system (bleed required), low water level (auto-fill valve issue), kettling (heat exchanger scale or extreme over-temperature), or steam hammer on steam systems (improper pitch causing water to collect in steam lines). Persistent unusual noise warrants diagnostic service before damage occurs.

Schedule Boiler Repair

For emergency dispatch (no heat below 50°F indoor, gas smell, water leak from boiler), call 24/7. For routine service, schedule online or call during business hours.

Emergency Line (24/7): (385) 300-1867
Address: 756 E Winchester St #322, Salt Lake City, UT 84107
Email: info@saltlakecityheatingairconditioning.xyz
Utah DOPL HVAC Contractor License: #11567823-5501
EPA Section 608 Universal (Lead Tech): #608U-2009-447129

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Office Hours

Emergency Service: 24 hours a day, 7 days a week
Office Staff: Monday – Friday, 8:00 AM – 5:00 PM
Closed: Weekends and State/Federal Holidays (emergency line always active)

Boiler Repair Salt Lake City | Hydronic Specialists