Tankless water heater rainwater entering vent in Greater Vancouver

Given how much rain Greater Vancouver gets, water finding its way into a tankless water heater's vent is a real concern. A small amount of moisture in a condensing vent is expected, but rainwater intrusion at the termination is not, and it can cause faults. Here is how to tell the difference.

Normal condensate versus rainwater intrusion

A high-efficiency condensing tankless unit naturally produces acidic condensate inside the exhaust as combustion gases cool, and that is drained away through a dedicated condensate line, not the vent termination. Rainwater intrusion is different: it means rain is entering the exhaust or intake from outside, usually because the termination is improperly pitched, missing its rain cap, or poorly positioned. Driving coastal rain and wind make this more likely here than in drier climates.

• Condensate forming inside the vent is normal and drains separately
• Rainwater intrusion enters from the outdoor termination
• Wind-driven coastal rain raises the risk in our region

Why rainwater in the vent matters

Water pooling where it should not be can interfere with combustion airflow, corrode components over time, and trigger fan, airflow, or fault codes. If enough water reaches the heat exchanger area or sensors, the unit may lock out to protect itself. Persistent intrusion is worth correcting promptly because it shortens the life of internal parts.

In older Vancouver homes, vent runs added during a furnace-to-tankless conversion sometimes have less-than-ideal slope or termination placement, which is a frequent source of this issue.

• Water can disrupt airflow and corrode internal parts
• It may trigger fan, airflow, or fault codes and lockouts
• Poorly sloped or placed terminations are a common cause

Safe checks and the right fix

From outside, you can visually confirm the vent termination has its proper cap or hood and is not damaged or blocked by debris. Beyond that, correcting vent pitch, sealing joints, and repositioning a termination involve combustion venting that a licensed gas technician must handle to code. Do not open or modify the venting yourself. If you ever smell exhaust indoors or suspect gas, leave the home and call your gas utility's emergency line first.

• Visually confirm the outdoor termination cap is present and intact
• Vent pitch, sealing, and repositioning are technician work
• Never modify combustion venting yourself
• Smell exhaust or gas indoors? Leave and call the gas utility first

Frequently Asked Questions

Is some water in my tankless vent normal?

A condensing unit produces acidic condensate inside the exhaust, but that drains through a dedicated condensate line. Rainwater coming in from the outdoor termination is not normal and should be corrected.

What causes rain to get into the vent?

Usually an improperly pitched vent, a missing or damaged rain cap, or a poorly positioned termination. Wind-driven coastal rain makes these flaws more apparent.

Can rainwater in the vent damage my heater?

Yes. It can disrupt airflow, corrode parts, and trigger fault codes or lockouts over time, so it is worth addressing promptly.

Can I fix the vent termination myself?

No. Correcting combustion venting must meet code and be done by a licensed gas technician. You can visually check that the outdoor cap is present and intact.

HeatLand Heating & Cooling is a licensed and insured, TSBC-certified HVAC company serving homeowners across Greater Vancouver. Our technicians diagnose the real fault, explain your options in plain language, and complete the work safely and to code.

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