Our customers ask us this question a lot, why does my water pressure drop?

One thing for sure, most times it can be an easy fix.

You’re heating system could be loosing pressure for a number of reasons. Heating system pressure drops can be caused from a small leak internal to the boiler, a faulty expansion vessel or a leak on the external pipe and fittings.

I will give you some advice that you can use before having to call a heating engineer.


If you have had a continuing flow of water coming from the pressure relief, there is a possibility that some dirt or contaminated water has blocked the seating of the pressure safety valve. If this is the case you will need to call one of or heating engineers out. The safety valve will most likely need replacing. This is a very inexpensive part and should cost around £15.00.



On a sealed heating system you will have an expansion vessel. The expansion vessel is in place to accommodate the extra water volume in the system as the water is being heated. ( AS WATER HEATS THE VOLUME WILL GROW BY 4%)

If the expansion vessel is faulty, it wont be able to handle the rise in system pressure, causing the safety valve to open and drain the excess water pressure. We can see this by looking at the pressure gauge, The pressure will rapidly rise.

If the doesn’t seem to be the issue, next find the Schrader valve on the expansion vessel. it looks similar to the air valve that you will have on your bike tyre. Press the pin, if water leaks from the valve. This indicates that the diaphragm with the vessel is faulty. If this is the case, one of our Belfast heating engineers will need to attend and carry out a boiler repair.

If air comes from the valve and the pressure rapidly rises while the heating system is on. This indicates that the diaphragm will need charging or a bigger vessel could be required for the property.

This will need attending to by one of our gas safe heating engineers in Belfast as the boiler will need drained. Please don’t work at a gas boiler unless you are gas safe registered and competent to do so. Call our heating engineers in Belfast for any gas boiler repairs.

Calibration of your expansion vessel should be done during regular boiler servicing. Having this done on a yearly basis will prevent this issue from occurring in the first place. When getting a boiler service, make sure you are getting a full boiler service and not just a quick safety check. Call Heating Solutions N.I to and book your gas boiler service.

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