Tankless water heater flow turbine clogged in Greater Vancouver

The flow turbine (also called the flow sensor) is the small spinning wheel that tells your tankless water heater how much water is moving through it. If it gets clogged or sticks, the unit can misread demand and refuse to fire. Here is what that looks like and what you can safely do about it.

How the flow turbine works

When you open a hot tap, water spins the flow turbine, and the control board counts those rotations to measure flow. The unit needs to detect a minimum flow before it will ignite the burner, so an accurate reading from this turbine is essential. Sediment, scale flakes, or debris from the supply line can foul the turbine and cause it to spin slowly, stick, or report the wrong flow.

In Greater Vancouver, fine sediment and the occasional scale flake from local water are typical culprits, especially in homes that have not had a descale or filter cleaning in a while.

• The turbine measures water flow so the burner knows when to fire
• A minimum flow must be detected before ignition
• Sediment and scale flakes can clog or stick the turbine

Signs of a clogged flow turbine

A fouled turbine often produces no hot water despite good flow at the tap, or hot water only at higher flow rates because the unit cannot sense lower draws. You may see a flow-sensor error code, or the unit may ignite intermittently. Because low-flow fixtures already sit near the minimum activation point, a partially clogged turbine makes those fixtures the first to lose hot water.

• No hot water even though the tap flows well
• Hot water only at higher flow rates
• Flow-sensor error codes or intermittent ignition
• Low-flow taps affected first

Safe checks and professional cleaning

Start with the easy items: clean the inlet water filter and confirm fixture aerators are not clogged, since both restrict the flow the turbine sees. If symptoms persist, the turbine itself likely needs cleaning or replacement, which involves opening the cold-water side of the unit and is best done by a licensed technician along with a full descale. Regular maintenance keeps the turbine and inlet filter clear and reduces these no-fire complaints.

• Clean the inlet water filter and fixture aerators
• Persistent flow errors mean the turbine needs professional cleaning
• Pair turbine service with a descale during routine maintenance

Frequently Asked Questions

What is a flow turbine in a tankless water heater?

It is a small spinning sensor that measures how much water is flowing so the unit knows when to fire the burner. The control board reads its rotations to detect demand.

What happens if the flow turbine is clogged?

The unit may fail to ignite even when water is flowing, provide hot water only at high flow, or throw a flow-sensor error. Low-flow fixtures usually lose hot water first.

Can I clean the flow turbine myself?

You can clean the inlet water filter and fixture aerators, which are the simple checks. Cleaning or replacing the turbine itself involves opening the unit and should be done by a licensed technician.

How do I prevent the turbine from clogging?

Keep up with regular descaling and inlet-filter cleaning. Removing sediment and scale before it reaches the turbine is the best prevention.

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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