A boiler that senses no water flow simply refuses to fire, and that safety interlock is exactly what a flow switch is built to enforce.
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Quick answer
Replacing a flow switch on a West Vancouver boiler generally falls within the typical boiler repair range of $250 to $1,800, with most of these jobs sitting near the $400 to $900 middle of that band, plus $90 to $150 for a diagnostic visit if needed. These are 2026 public-market ballparks, not a fixed quote — CANRO's certified gas technicians confirm the exact price after checking whether the switch itself, or a circulator failing to move water at all, is the actual cause. Ruling out a pump problem first is a key part of getting this diagnosis right.
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A flow switch is a safety interlock installed in the piping near the boiler that confirms water is actually circulating before allowing the burner to fire, or shutting it down if flow stops mid-cycle. Without confirmed flow, a boiler firing into stagnant water risks localized overheating and damage to the heat exchanger, so the switch exists specifically to prevent the boiler from ever running dry or against a stalled pump.
When a flow switch itself fails — as opposed to genuinely detecting a real flow problem — it typically fails in the safe direction, keeping the boiler from firing even though water is actually moving fine.
Before replacing a flow switch, a technician has to confirm actual water flow is present using a separate check, since replacing the switch won't help if the real problem is a failing circulator pump, a closed isolation valve, or trapped air blocking circulation. Once flow is confirmed and the switch itself is isolated as the fault, the swap itself is usually straightforward.
| Item | Typical range (CAD) | Notes |
|---|---|---|
| Diagnostic / service call | $90 – $150 | Confirms actual flow before replacing the switch |
| Flow switch replacement | $250 – $1,800 (most $400 – $900) | Straightforward swaps trend toward the lower-middle |
| Licensed gas/HVAC labour | $95 – $165 per hour | Includes refilling and purging air if the loop was opened |
A quick swap with isolation valves already in place and no underlying flow problem sits at the lower end. Costs rise if the whole loop needs draining, if the real issue turns out to be a failing circulator that needs its own separate repair, or if trapped air elsewhere in the system is muddying the diagnosis and needs to be addressed as part of the same visit.
West Vancouver's older cast-iron radiator systems, more common in some of the pre-1980s British Properties homes, sometimes have flow switches installed in less accessible spots than a newer, purpose-designed mechanical room would, which can add modest time to the job.
If the flow switch itself is confirmed faulty, replacing it is a routine repair. If the underlying cause turns out to be the circulator pump not moving water adequately, that's a separate and sometimes more involved repair, and it's worth having a technician clearly identify which one applies rather than replacing the switch first and hoping it resolves an issue that actually lives elsewhere in the system.
Safety note
The flow switch is a safety interlock preventing a gas-fired boiler from firing without confirmed water circulation. This work should be done by a Technical Safety BC licensed gas fitter — CANRO holds gas licence LGA0043870 and boiler licence LBP0046450. If you ever smell gas near the boiler, leave the home and call FortisBC at 1-800-663-9911.
In West Vancouver, most jobs fall within $400 to $900 of the broader $250 to $1,800 boiler repair range, plus a $90 to $150 diagnostic visit if needed. Confirming actual water flow before replacing the switch is part of getting the diagnosis right.
A faulty flow switch can report no flow even when the circulator is actually moving water fine. A technician tests actual flow separately to confirm whether the switch or the pump is really at fault.
Yes, and that's exactly why diagnosis matters before replacing parts. A weak or failed circulator can trigger the same flow-fault symptom as a bad switch, but the repair and cost are different.
Occasional resets aren't dangerous, but repeated lockouts mean the safety interlock is doing its job correctly and something needs proper diagnosis rather than continued resetting.
It can contribute to inconsistent flow readings in some systems, which is one more reason a full diagnostic check matters rather than assuming the switch itself is always the cause.
There's no fixed lifespan. Many last the life of the system, while sediment or corrosion can cause earlier failure in some installations.
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