Having a home boiler is an excellent way to keep your home warm and comfortable during the colder months of the year. As with any home appliance, they require regular maintenance and repair to remain functional and use energy efficiently while regulating temperatures. Adhering to a regular schedule of care will help you to avoid untimely breakdowns, reduce your energy costs, and ensure that your boiler system lasts for years to come.

About Boiler Pressure

Maintaining proper boiler pressure is important because it ensures safe and efficient operation, prevents dangerous situations, and helps maintain hot water flow throughout your home. Providing proper maintenance that checks pressure regularly ensures that your boiler will serve you well for the duration of its lifespan, and it may even save you money on monthly energy costs.

High Pressure

High boiler pressure indicates a malfunction somewhere in the pressure control system of the boiler. This can be caused by several factors, including:

  • Leaks in the system
  • A faulty pressure relief valve
  • A problem with the expansion vessel
  • A buildup of pressure due to trapped air or water

Excessively high pressure can lead to damage to the boiler or even an explosion if measures are not taken to correct the upward climb.

Low Pressure

While the correct amount of pressure varies by both model and manufacturer, most combination boiler systems require a pressure of 1 to 1.5 bar when cold. As it begins to heat water, any increase in pressure that is seen by the system as too high will be discharged out of your system by the pressure release valve. Your boiler may be losing pressure because water is escaping somewhere from the central heating unit. If you cannot find the source of the leak but the boiler pressure keeps dropping, you may have internal components as the culprit of your pressure drop. Adding water may be a short-term fix for a while, but anytime you add oxygen-rich water to a closed system, you are encouraging components within the system to rust from the inside out, thus shortening the life of your unit.

Finding the Leak

Checking various fixtures and parts of your system will quickly reveal where your pressure issue is as well as give you a good idea of what will need to be repaired in order to restore service once more. Check these areas to see if they have been compromised.

Pressure Release Valve

In the absence of visible leaks around your home, your leak may have something to do with the boiler itself. A faulty pressure release valve will allow water to exit the system when it shouldn’t. Check your PRV pipe to see if it is dripping. Other signs that a leak is present include residual lime buildup and a change in the color of the surrounding area. Common reasons for the PRV to fail include:

  • Valve will not remain closed.
  • Washer inside the valve has become compromised or corroded.
  • Valve has been jammed or opened due to corrosion.
  • Valve is jammed due to a faulty expansion vessel.

Replacement will be necessary in these cases to ensure that your system, and correct pressure, are restored.

Faulty Expansion Vessel

The expansion vessel of a boiler is comprised of two internal compartments separated by a rubber diaphragm. One chamber contains water from central heating, and the other contains pressurized air. As water expands, the air is compressed, with the reverse taking place as the water cools in the unit.

If air pressure inside the expansion valve is too low, the system has no way of being able to accommodate changes in water volume. Water will then discharge through the pressure release valve. Eventually, enough water will flow out of your system, and your boilers simply won’t light. Seeing water flowing out of the top of an expansion vessel is not good news either; it’s a clear sign that you need to replace the expansion vessel to restore pressure in your unit.

Frozen Pipes

If you live in areas prone to extreme highs and lows in temperature, you may develop frozen pipes. From time to time, frozen blockages can build up and restrict water flow, causing a drop in pressure within your system.

Thermostat Miscommunications

A faulty thermostat can cause low boiler pressure because it affects the temperature control of your whole system. This inability to regulate temperatures can cause your system to switch off prematurely before warming water has had a chance to increase proper levels of pressure in your system.

Issues With the Loop System

If you’ve inspected various parts of your boiler and all seem functional and working as intended, then it’s time to examine your loop. This is a trickier business than it might seem, for you may not always see the consequences of a water leak somewhere in your system. It could be hiding under floorboards or in walls, wreaking havoc with every passing day. Having a professional heating technician examine the parts of your system as a way to identify your leak is the best line of defense against continued dropping pressure, water damage, and even mold and mildew growth that can affect indoor air quality and wreak havoc on your respiratory health.

Potential Dangers of a Home Boiler System

As with other heating systems, failing to maintain your boiler properly could result in a number of dangerous situations that may cause damage to your home and injury to you and your loved ones.

Carbon Monoxide Poisoning

Boilers that burn fuel to heat water for circulation can release harmful carbon monoxide, a tasteless, odorless gas that can be fatal if inhaled in concentrated doses. Some of the symptoms of carbon monoxide poisoning include:

  • Headache
  • Weakness
  • Dizziness
  • Nausea and vomiting
  • Shortness of breath
  • Confusion
  • Blurred vision
  • Loss of consciousness

Getting your boiler maintained and inspected regularly will reduce your risk of carbon monoxide poisoning.


Boiler explosions occur due to improper installation, lack of maintenance, and failure to repair when needed. These incidents can cause property damage and personal injury to you and your loved ones.

Gas Leaks

Improperly installed and maintained gas connections leading to boilers can lead to gas leaks, posing both fire and explosion hazards. If you notice a rotten egg smell around your boiler, you could have a gas leak and should consult with a professional.

Need a Boiler Repair?

Bel-Aire Heating & Cooling serves valued clients in West Michigan and beyond. We provide 24/7 emergency service, furnace and AC repair, installation, and maintenance, boiler services, and commercial and geothermal services that help heat and cool your home more efficiently. Our personal commitment to your satisfaction is what makes us a premier service provider for all of your HVAC heating and cooling needs. Don’t wait till your boiler pressure leaves you out in the cold; call us today for an assessment and repair of your valuable system. We’ll get you up and running again in no time!

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