If your boiler keeps your Metro Vancouver home warm but the taps run cold, the fault is almost always isolated to the domestic hot water side — commonly a diverter valve, heat exchanger, or sensor issue that needs a licensed technician to diagnose.
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Quick answer: A boiler that heats your home but produces no hot water usually points to a problem isolated to the domestic hot water side of the system — most often a failed diverter valve, a faulty plate heat exchanger (limescale-clogged from Metro Vancouver's moderate-hard water), a bad flow sensor or thermistor, low system pressure, or a hot water priority setting that's misconfigured. Central heating uses a separate circuit path, so it can keep working even when the hot water function fails. Diagnosis requires a licensed gas technician.
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Most residential boilers — especially combi boilers common in Metro Vancouver condos and townhomes — use two separate paths for the water they heat. One path circulates hot water through your radiators or in-floor loops for space heating. The other diverts water through a plate heat exchanger on demand, the moment you open a hot tap, to heat your domestic water instantly. Because these are functionally separate circuits controlled by different components, it's entirely possible for the heating circuit to keep working normally while the domestic hot water path fails on its own. That's exactly why you can have a warm house and a cold shower at the same time.
This split-circuit design is efficient and space-saving, which is why it's popular in the condos and townhomes that make up so much of the region's housing stock. The tradeoff is that a single failed part on the hot-water side — while the rest of the boiler runs fine — is a common and fairly predictable failure pattern, not usually a sign the whole unit is dying.
| Cause | What's Happening |
|---|---|
| Faulty diverter valve | The valve that should redirect flow to the hot water heat exchanger sticks in the heating-only position |
| Clogged or failing plate heat exchanger | Mineral scale or debris restricts water flow through the hot water exchanger over years of use |
| Bad flow sensor or flow switch | The boiler can't detect that a tap has opened, so it never triggers hot water mode |
| Faulty thermistor or sensor | A failed temperature sensor on the domestic hot water side sends bad readings, causing the boiler to withhold heating |
| Low system water pressure | Pressure below the manufacturer's minimum can prevent the hot water function from firing even though central heating still runs |
| PCB (circuit board) fault | The control board correctly fires the heating circuit but fails to trigger the hot water sequence |
| Hot water priority or scheduling setting | On some systems, a misconfigured control or timer setting can effectively disable hot water while leaving heating scheduled normally |
Age and water quality both play a role. Even though Metro Vancouver's water isn't considered severely hard, years of mineral deposit inside a heat exchanger's narrow waterways can gradually restrict flow until hot water output drops off or stops altogether.
If any of these steps resolve the issue, great — but if the pressure keeps dropping, the same fault code reappears, or a reset only fixes things temporarily, that points to an underlying mechanical or electrical fault that needs a professional look.
A licensed CANRO technician can diagnose it accurately — same-day response across Metro Vancouver.
📞 (604) 359-1081 Request a free quoteAnything beyond checking pressure, settings, and a single reset should go to a licensed technician. Opening the boiler's casing, testing or replacing a diverter valve, flow sensor, thermistor, or circuit board, and any work on the gas line itself all require a Technical Safety BC licensed gas fitter under BC law — this isn't optional, and it isn't a DIY-friendly repair even for handy homeowners. Boilers combine gas combustion, pressurized hot water, and line-voltage electrical components in a compact space, and misdiagnosing or mishandling any of them creates real safety risk.
CANRO's technicians hold Technical Safety BC gas licence LGA0043870 and boiler licence LBP0046450, and our Red Seal certified team carries WorkSafeBC coverage for every job.
Because the same symptom can come from several different components, an in-person diagnosis is the only reliable way to know which part actually failed — guessing based on symptoms alone often leads to replacing the wrong part.
Repair cost depends on the specific part involved — a sensor or valve repair is typically much less than replacing a full heat exchanger. Rather than guessing, factors like the age of your boiler, parts availability for your model, and whether this is a repeat failure all factor into whether repair or replacement makes more financial sense. If your unit is older and nearing the end of its service life, a technician can walk you through current CANRO figures for a high-efficiency boiler replacement, which for Metro Vancouver homes typically runs $7,500-$15,000+ installed before rebates, depending on sizing, venting, and any gas line or permit work involved. Current programs like the interest-free Canada Greener Homes Loan (up to $40,000), the Oil to Heat Pump Affordability program, and CleanBC, BC Hydro, or FortisBC rebates may apply depending on your situation — exact figures change, so confirm current eligibility and amounts at quote time.
⚠️ Safety note: This is not a gas-emergency scenario on its own, but if you smell gas (a rotten-egg odour) anywhere near the boiler, do not investigate further — leave the home immediately, avoid switches or open flames, and call the FortisBC emergency line at 1-800-663-9911 from outside. Combi and system boilers involve gas, high-temperature water, and mains electrical connections; under BC law only a licensed gas fitter may open the gas line or replace internal components like a diverter valve, heat exchanger, or PCB. If you ever notice soot, a yellow/orange burner flame instead of blue, or your carbon monoxide alarm sounds, leave the house, get to fresh air, and call FortisBC or 911 before calling for repair.
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📞 (604) 359-1081 Request a free quoteReviewed by the CANRO Heating & Cooling service team — June 30, 2026. CANRO holds Technical Safety BC gas licence LGA0043870 and boiler licence LBP0046450, employs Red Seal certified technicians, and carries WorkSafeBC and liability insurance. 4.9★ from 85+ Google reviews · serving Metro Vancouver since 1999 · (604) 359-1081 · info@canroheat.ca.
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