Why does my heating system lose pressure?
Pressure loss may be caused from a leak in the pressure relief valve, an issue in the expansion vessel, air in your system, or a leak in the heating pipework itself.
What happens when expansion vessel loses pressure?
If your boiler keeps losing pressure it could be from a failure in the expansion vessel. The expansion vessel is also known as an expansion tank. The expansion vessel prevents the boiler pressure relief valve, releasing water to reduce pressure, simply from the expansion caused by the hot water.
How do I increase the pressure in my expansion vessel?
If the expansion vessel has been checked via the Schrader valve and the pressure is too low, it will require recharging or re-pressurising to the correct pressure. This can be done using a car foot pump or similar device. Connect a suitable air pump to the Schrader valve to increase the pressure in the pressure vessel.
What happens if my expansion vessel fails?
If the expansion tank is missing or not operating properly, pressure in the system may cause the boiler’s pressure relief valve to vent water. Or, air bubbles being released by the heating water may gather somewhere else in the system, causing a blockage that stops the flow of hot water.
Can a pressurised heating system be dangerous without an expansion vessel?
Without one, the system cannot allow cold water to expand as it is heated and therefore a system can become dangerous. The basic principles of a pressurised heating system lay in the use of an expansion vessel. Watch the video below for an in depth view inside an expansion vessel and for a guide as to how they work.
What should the pressure be for an expansion vessel?
Dependant on various parameters, the system will need to be topped up to a specific pressure. The standard setting is 1 bar cold, but depending on the design of the system etc., it may differ. Once the system pressure has been set with the boiler cold, and the boiler is turned on, the water within it will start to heat and expand.
What causes an expansion vessel fault in a central heating system?
If you have a sealed central heating system, sooner or later you will get expansion vessel faults. They are quite common and we’ll tell you how we deal with them. Above 4°C, water expands when heated and contracts when cooled. Expansion of water in a sealed system causes a rise in pressure and contraction causes a drop in pressure.
How much air pressure does a pressurised heating system need?
With out this automatic expansion a pressurised heating system would not work and could even become dangerous. Some important things to consider is the air pressure inside the expansion vessel. It rarely needs to be anything more than 1.5 bar in most domestic properties.
Dependant on various parameters, the system will need to be topped up to a specific pressure. The standard setting is 1 bar cold, but depending on the design of the system etc., it may differ. Once the system pressure has been set with the boiler cold, and the boiler is turned on, the water within it will start to heat and expand.
Can a leak in a sealed heating system cause pressure loss?
If its a leak under ground floor then there will be no evidence. And similarly could be a heat exchanger and the water is evaporating. Leaks are hard to find, sometimes you have to use internal leak sealer which works a treat! When the gas man emptied the boiler/system using the prv the water came out slightly discoloured with a hint of green.
How can you tell if an expansion vessel is faulty?
you can’t really tell from pressure needle, if the pressure needle drops yes it is one of the signs that expansion vessel is faulty but at the same time there may be leak somewhere that causing pressure loss. and when the system works you can see the rise on the pressure gauge.
If you have a sealed central heating system, sooner or later you will get expansion vessel faults. They are quite common and we’ll tell you how we deal with them. Above 4°C, water expands when heated and contracts when cooled. Expansion of water in a sealed system causes a rise in pressure and contraction causes a drop in pressure.
