Boiler Zone Valve Issues: 4 Signs to Look Out For

by Team eLocal
Plumber adjusts gas boiler before operating.

Boiler zone valves are an oft-overlooked part of many home heating systems, and many homeowners are unsure what their zone valves are or what they do.

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However, understanding how to spot boiler zone valve problems can help you avoid expensive boiler repairs in the long run.

First Things First: What Is a Boiler Zone Valve?

Boiler zone valves control the amount of hot water traveling to a specific zone inside your home. Not all boilers have zone valves; you'll only have them if your heating system divides into different zones, allowing you to set different temperatures for individual areas.

These heating systems have individual thermostats for each zone or piping loop, and each thermostat connects to a boiler zone valve. The valve opens when you set the thermostat to increase the temperature in the corresponding area, allowing more hot water to flow into the system. Conversely, the valve can reduce or cut off the flow of hot water when you turn the thermostat down.

Most zoned heating systems have a minimum of two zone valves. You can usually find these valves adjacent to your boiler, hence the name "boiler zone valves." However, some systems have zone valves installed on other parts of the piping loop.

What Are the Signs of a Faulty Boiler Zone Valve?

Boiler zone valves handle high temperatures, which can cause the components to wear out over time. Faulty zone valves can cause significant issues if you don't address them promptly because they can decrease your boiler's efficiency and lifespan. Furthermore, you could find yourself uncomfortably hot or cold if your zoning system doesn't work correctly.

The following signs can indicate an issue with your boiler zone valves:

1. No Heat

The most obvious sign of a broken or faulty boiler zone valve is a zone that won't heat up at all. A zone valve in proper working order will open as soon as you turn on the zone thermostat, causing the pipes to heat up. Try turning on the thermostat and feeling the surrounding lines to determine if the valve is working correctly.

2. Uneven Heating

You may also notice that some heat zones inside your home feel too cold or warm. Boiler zone valves can jam shut, but they can also jam open. When this happens, the valve will allow hot water through, whether you want it or not, as soon as you turn on the thermostat to any zone in your house. For example, you may turn on the thermostat to warm up your bedroom and find that your system also heats your kitchen or bathroom.

Many boiler zone valves have a manual switch that allows you to override the thermostat instruction to open or close the valve. Sometimes, homeowners keep the valve open using the manual switch to avoid having to repair or replace a faulty boiler zone valve. This means that hot water automatically enters the pipe when you turn on any thermostat, preventing the zoning from working correctly. If you recently moved into a new home and the manual switches are set to on, you may have a faulty valve on your hands.

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3. Leaking Valves

Damaged boiler zone valves sometimes leak water. You can often repair leaks coming from the connections between the pipe and the valve by draining the pipe and resoldering the joints. However, leaks coming from the valve itself are more challenging to repair, and it's often better to replace the boiler zone valve altogether.

4. Banging or Hammering

Changes in pressure can cause boiler zone valves to make a loud banging or hammering sound when you turn the thermostat on or off. Your heating system may still work, but ignoring the problem can increase the risk of leaks. Switching to slow-close boiler zone valves can potentially resolve the issue by preventing sudden pressure changes.

When to Call a Plumber

It's worth remembering that other heating system faults can cause problems, such as uneven heating or alarming noises. For example, a faulty thermostat could be an alternative explanation for zones that feel too hot or cold.

You may be better off calling a professional plumber to diagnose and repair your heating system unless you have significant plumbing knowledge. Otherwise, you could end up replacing the boiler zone valves only to find that another component is to blame.


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