To tell if there is enough water in your boiler regularly check the water gauge or sight glass on the front of the boiler. The gauge or glass should have a safe range marked on it, usually by two lines or dots. Some modern boilers also have a digital display. If the boiler water level is low it should be topped up by opening the feed water valve.
One overlooked cause of boiler breakdowns is a lack of sufficient water. Keeping your boiler’s water levels in check can prevent costly repairs and guarantee steady performance.
This article will teach you how to determine if your boiler has enough water to function properly. We also provide step-by-step instructions on how to check the water level, and what to do if the water level is low. There is a bonus guide on how to refill the boiler as well.
Step-By-Step Guide: How to Check Boiler Water Level
Checking the water level in your boiler is a simple but essential task. It needs to be done routinely to make sure your boiler continues to operate safely and efficiently.
Here is a step-by-step guide on how to check the water level in your boiler:
1. Locate the water gauge or sight glass
The water gauge or sight glass is usually located on the front or side of the boiler.
It is a clear, clear glass tube that allows you to see the water level inside the boiler.
2. Check the water level
Look at the water gauge or sight glass and make sure the water level is within the safe range indicated.
The safe range is usually marked by two lines or dots on the gauge.
If no range is marked on the sight glass, then usually having some water visible in it means it has enough (though not always). It is important to become familiar with what a normal level of water in your boiler looks like on your sight glass (or gauge).
It’s best to look at your sight glass when the boiler feed water pump is not running. This will show you what the standing water level is in the boiler. If you can go to the boiler when the feed water pump turns on you will see the water level in your sight glass that indicates the pump needs to turn on. If the sight glass is not marked, then you can mark it yourself with a permanent marker or a piece of plumbing tape. This way you can use the mark in the future as an easy guide for water level.
Note: There are also some modern boiler systems that have a digital display on them. The safety range and water level should be clearly displayed. If you screen has gone blank there may be a fuse issue and a plumber or technician should be brought in.
3. Refill or drain as needed:
If the water level is too low, locate the designated fill valve and open it fully, while monitoring the water gauge or sight glass until the proper water level is reached. (see detailed instructions below)
Note: If the water level happens to be too high, locate the drain valve and open it to release the excess water until the appropriate water level is reached.
4. Repeat the process
Check the water level regularly to make sure it stays within the safe range.
It’s essential to follow the manufacturer’s recommendations and keep the water level within the safe range of your specific boiler to avoid damage to the system, reduced heating efficiency, or even potential safety hazards.
Note: If the water level in your boiler seems to keep dropping then there may be an underlying problem. Boilers can have low water naturally over time, but damaged or old feed water pumps or control valves can create an ongoing problem of low water.
If you have any doubts or concerns about the water level in your boiler, you should contact a professional plumber.
If you find that you need to keep topping up your boiler (more than usual) Water Purification Guide has a troubleshooting guide available here.
How to Add Water to a Boiler System
To add water to your boiler system, you will need to follow these steps:
1. Turn off the power
Once you have turned the power off to the boiler unit you will need to wait a while to allow the system to cool down completely.
2. Locate and turn off the feed water shutoff valve
The feed water shutoff valve is usually near the bottom of the boiler.
In some boilers, the process of topping up water is automatic. In older boilers, you may need to add water manually.
3. Open the feed water valve (automatic filling boilers)
Carefully open the feed water valve. If your boiler lets water in automatically, all you have to do is monitor the water level as the water pours in.
Once the water level reaches the safe range indicated on the water gauge or sight glass, close off the feed valve.
Manual water top up (for older-style boilers)
For manual boilers, you have to pour the water in yourself using a hose or a bucket. As you pour, keep your eyes on the sight glass as well.
4. Close the valve and turn the power on
Once you have closed the feed water valve (and reopened any other valves you closed) to the boiler and turned the power back on, recheck the water level to make sure it stays within the safe range.
If you have any doubts or concerns about the process, we recommend you call a plumber.
Adding water to a boiler system will require you to locate the designated feed valve and turn it open while monitoring the water gauge or sight glass until the appropriate water level is reached.
The locations of the feed valve and water gauge vary between boilers but are usually fairly obvious.
How Much Water Should Be in A Boiler?
The amount of water in a boiler depends on the specific model and manufacturer’s recommendations.
It is important to follow the manufacturer’s guidelines for the proper water level as indicated on the boiler system.
Generally, the safe range is usually indicated on the gauge or glass. If the water level drops below the safe range, it should be refilled to that level.
Overfilling the boiler can cause pressure to build up, leading to potential safety hazards.
What Happens If the Water Level in a Boiler is Too High?
Having too much water in a boiler can lead to several problems, which can affect the safety and efficiency of the system. Here are some of the potential consequences of a high water level in a boiler:
Overheating
A high water level in the boiler can cause overheating, as the excess water acts as a heat sink and reduces the temperature difference between the water and the steam.
This can lead to high-temperature steam and overheating of the boiler, which can cause damage to the metal components and reduce the system’s efficiency.
Water hammer
When the water level in the boiler is too high, it can cause a water hammer, which is a sudden and violent movement of water in the pipes.
Water hammers can cause damage to the pipes, fittings, and valves and can also cause noise and vibration in the system.
Safety hazards
A high water level in the boiler can cause water to be expelled through the safety relief valve, which is designed to prevent the pressure from building up to dangerous levels.
The expulsion of water through the safety relief valve can be a safety hazard, as it can cause water to spill onto the floor and create a slipping risk.
Reduced efficiency
A high water level in the boiler can cause the system to work less efficiently. It reduces the temperature difference between the water and the steam.
This can lead to reduced heating efficiency and higher energy costs.
If the water level in a boiler is too high, it can cause overpressure, reduced heating efficiency, and some other problems, which can all impact the performance and safety of the system.
What Happens If the Water Level in a Boiler is Too Low?
When the water level in a boiler is too low, it can result in several problems, including damage to the heat exchanger and other components, reduced heating efficiency, and increased energy consumption.
A lack of water in the boiler can also cause it to overheat, which can pose a safety hazard by increasing the risk of explosion, electrocution, or damage to the boiler’s system.
To prevent these issues and ensure safe and efficient operation, it’s important to maintain the proper water level in the boiler (as indicated by the manufacturer’s guidelines and on the boiler itself).
What is the Lowest Permissible Water Level in a Boiler?
The lowest permissible water level in a boiler is an important safety consideration, as a low water level can cause damage to the boiler and even create a safety hazard.
Generally, the minimum water level in a boiler should be at least 2 inches above the danger point, but this can vary depending on the design and type of boiler.
If the water level falls below the minimum permissible level, the heat exchanger tubes can become overheated and damaged.
This can cause leaks and even a complete failure of the boiler.
A low water level can cause water hammer, which is a sudden and violent water movement in the pipes and can cause damage to the pipes, fittings, and valves.
Water Purification Guide also has detailed information on how to know if your water heater (not boiler) is leaking from the top, and how to fix it, available here.
