Boiler make up water valve feeding constantly in Greater Vancouver

A boiler's make-up water valve (auto-fill valve) is meant to top up the closed loop only occasionally, keeping pressure in range. If it's feeding water constantly, the system is losing water somewhere or the valve isn't holding, and that's worth diagnosing before it causes other problems.

Why the fill valve keeps feeding

In a sealed hydronic system, the make-up valve should rarely need to add water. If it's running continuously, the most common explanation is a leak somewhere in the loop that the valve keeps trying to replace, or a valve that has worn and no longer shuts off at the correct pressure.

Constant feeding causes its own trouble. Fresh water introduces oxygen and minerals that accelerate corrosion and sludge, and it can push pressure too high, leading to relief-valve dripping. In older Greater Vancouver systems, small leaks at fittings, vents, or the pump can quietly trigger constant make-up flow.

• A leak in the loop the valve is trying to replace
• A worn pressure-reducing valve that won't close
• A failed expansion tank letting pressure swing
• Constant fresh water feeding corrosion and sludge

Safe checks before calling a pro

Look around the system for visible water at fittings, the pump, air vents, and the relief-valve discharge, since a leak is the most common driver. Watch the pressure gauge over time and note whether it holds steady or keeps drifting. Confirm the thermostat is cycling normally.

Adjusting or replacing the fill valve, and tracking down internal leaks, are licensed-technician tasks because they involve the pressurized system. Avoid manually overriding or wiring open the fill valve, which can over-pressurize the boiler.

• Inspect for visible leaks at fittings and components
• Track the pressure reading over time
• Note where any water is collecting
• Leave valve service and leak repair to a pro

Frequently Asked Questions

Is constant make-up water bad for the boiler?

Yes. Repeatedly adding fresh water brings in oxygen and minerals that speed up internal corrosion and sludge, shortening the life of components, so the cause should be found and fixed.

Could it be a leak I can't see?

Often, yes. Leaks can hide inside walls, under floors, or within the boiler. A technician can pressure-test and inspect to locate a hidden loss the fill valve is masking.

Can I just shut off the make-up valve?

Closing the feed isn't a fix and can leave the system short on water. The underlying leak or valve fault needs proper diagnosis by a technician.

If the boiler is failing from corrosion, are rebates available?

If replacement is needed, eligible high-efficiency gas boilers can qualify for FortisBC and CleanBC rebates in BC. HeatLand can confirm what's currently available.

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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