If you've ever looked at your home's steam boiler, you've probably noticed that it has several valves. Boilers vary by age, make, and model, but most modern units have many features in common. While the valves you're likely to find around your boiler serve critical roles, they're also potential failure points. Clogs and leaks at these valves can stop your boiler from working or even flood your basement.
While this guide won't provide a definitive explanation of how your boiler works, it will explore three of the common valves that may fail on your unit. Understanding the purpose of these valves can help you spot trouble before it becomes too severe.
1. Sight Glass Valves
Every steam boiler should contain a sight glass that allows you to view the current water level in the tank. You can quickly identify the sight glass by looking for a glass tube outside the boiler. Depending on your boiler's age and whether you've ever changed the glass, you may find this tube stained with rust or other deposits.
Boiler sight glass tubes usually have a valve on both the top and bottom to allow water to enter and steam to leave. Water can also flow from the top pipe back into the boiler if you've overfilled your tank. A leaky or clogged valve can stop you from monitoring your boiler's water level, potentially making your boiler unsafe to operate. Never ignore leaky valves or empty sight glass tubes.
2. Low-Water Cutoff Valve
Boilers need an adequate amount of water to operate safely. If the tank level falls too low, the boiler can overheat and potentially even explode. The low-water cutoff valve helps prevent this situation by shutting down the boiler burners when the tank level falls below a preset amount. These valves are like more sophisticated versions of the float valves you can find in toilet tanks.
Cutoff valves require routine maintenance because they can become clogged with gunk and debris that may prevent the float from moving freely. A stuck float can be a safety hazard, or it can stick in the low-water position and stop your boiler from running. If you suspect a problem with this valve, it's a good idea to avoid using your boiler until you can repair it.
3. Automatic Feed Valve
Your automatic feed valve adds water to your system to compensate for losses due to steam vents or other issues. This valve can become stuck closed, causing your system to run low on water. It may also stick in the open position, feeding excess water, overfilling your boiler, and causing the relief valve to dump water to relieve pressure.
While a stuck feed valve usually isn't a safety hazard, it's not something you should ignore. Overfilling your boiler can cause premature wear, and it can become dangerous if your relief valve isn't working correctly. If you notice your boiler overfilling, always contact a technician to investigate the problem as soon as possible. And if you suspect your boiler is malfunctioning, it is always a good idea to contact a boiler repair professional.