A tankless water heater's inlet filter is a small mesh screen with a big job: keep sediment out of the flow sensor and heat exchanger before it causes bigger problems.
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Quick answer
The inlet filter sits at the cold-water entry point of a tankless water heater, catching sediment, scale flakes, and debris before they reach the flow sensor and heat exchanger downstream. Over time this screen collects enough buildup to restrict flow noticeably, which can trigger flow-related faults or reduce hot water output even though the unit itself is working fine. Cleaning is often enough, but a damaged or heavily corroded screen needs replacing outright.
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| Filter condition | Recommended action |
|---|---|
| Light sediment, mesh intact | Clean and reinstall |
| Heavy scale crust, mesh still intact | Clean thoroughly, monitor for recurrence |
| Torn mesh or visible corrosion | Replace the filter screen outright |
| Filter missing or never installed | Install one — a cheap safeguard for the flow sensor |
An inlet filter is one of the least expensive parts in a tankless system, but it protects some of the more expensive ones downstream, particularly the flow sensor and heat exchanger. A technician doing routine tankless maintenance in Port Coquitlam will typically check this filter every service visit simply because it's quick to inspect and catches problems before they migrate further into the unit.
Because Metro Vancouver draws from a soft, low-mineral reservoir supply, ordinary scale buildup on an inlet filter tends to be gradual across the region, Port Coquitlam included. Where filters clog faster is usually tied to a specific local event — a watermain break or repair nearby, new construction activity disturbing older pipe sediment, or a home's own older galvanized supply line shedding rust internally.
Tankless units are especially common in the townhome and condo developments built over the past two decades near the West Coast Express corridor, and because these units run more total draws per year than a typical single-family tank setup, their inlet filters tend to need inspection on a more regular schedule than a homeowner might expect from a 'small screen' part.
Safety note
This component is part of a gas-fired, pressurized heating or hot water system, so work on it 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 appliance, leave the home immediately and call FortisBC at 1-800-663-9911 before doing anything else.
Some manufacturers design the housing for homeowner access, but shutting off and isolating a gas-fired appliance's water supply correctly matters, so many Port Coquitlam homeowners still have a technician handle it, especially the first time.
Most manufacturers recommend inspection during annual service, though a household with visibly sediment-heavy water or recent nearby plumbing work may want it checked sooner.
Left unaddressed, restricted flow can strain the flow sensor and contribute to scale settling elsewhere in the unit, so it's worth addressing before it causes downstream faults rather than after.
A sudden drop, especially after nearby municipal work, often means sediment has been stirred up and caught in the inlet filter. A technician can usually confirm and clear this quickly.
No — the inlet filter is a simple mesh screen positioned ahead of the flow sensor specifically to protect it. They're separate parts, though a clogged filter can sometimes mimic flow sensor symptoms.
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