How to Fix Rising Boiler Pressure

A water boiler in a basement

Several factors contribute to the efficiency of a boiler. All the heating system parts need to be in good working condition. Adequate fuel must be constantly available, whether powered by diesel, natural gas, or oil. The water tank must always have adequate water. Temperature and pressure settings must also be correct. You may sometimes experience rising pressure in the system. Below are four possible causes and actions to take.

Expansion Vessel

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This is found at the rear of the heating system. It regulates pressure rises in the system. It sometimes becomes necessary to re-pressurize this vessel to prevent frequent rising pressure in the set-up. First, turn off the boiler. Drain all water from the radiators. Then use a bicycle pump or foot pump to pressurize the vessel to a bar level of 1 to 1.5. Refill the radiators. Turn on the system. It should now work properly without any pressure problems.

Expansion Tank

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This feature is supposed to accommodate the expanding water levels in the system. A blockage in the pipe that leads into the expansion tank can hinder the smooth flow of water. Check the connecting pipe for any blockages. Dirt and debris may have accumulated with time. Clear the pipe and fit it back into the system.

Too much water in the expansion tank and too little air may also cause pressure to rise frequently. If the bottom of the tank does not feel hotter than the top, it indicates an excessive amount of water. You need to drain this water from the tank. To do so, first turn the boiler off. Then close the water shutoff valve and allow the system to cool. Attach a hose to the combination valve on the expansion tank. The combination valve will release water from the system and allow air in.

You should drain 3 to 4 gallons of water. If your system is an older model, it is unlikely to have a combination valve. Simply close the valve between the expansion tank and boiler and then completely drain the tank. Open the water supply valves and refill the system. Pressure should remain stable during subsequent use. The expansion tank may also have some defect. It is best to replace the tank if it appears damaged or worn out.

Air Lock

Occasionally, air may get trapped within the heating system. Pockets of air can cause the pressure to rise. To eliminate air pockets, you need to bleed your heating system. This will help to stabilize pressure. Obtain a small key from a hardware shop. Explain that you need to bleed your boiler. Fit the key into the slot at the radiator. Slowly turn it to release pressure until you attain the desired level.

Defective Valves

Sometimes, a valve in the system may be faulty. This may cause water to seep into the heating circuit. Pressure will then keep rising beyond the recommended level. The pressure relief valve will then open and begin to drip. Replace the faulty valve to correct the situation. This will also stabilize pressure.

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