Tuesday, November 27th, 2018
Boiler loses pressure ? Your combi boiler can be losing pressure for a number of reasons but the good news is that low pressure is relatively easy to diagnose and, in some cases, you can put it right yourself. Listed Below are a number of reasons to why your boiler has low pressure and how to fix it.
Your boiler will heat cold water that flows around the pipes and radiators throughout your home. The water pressure in your home needs to be stable for it to work efficiently. Water pressure in most modern combination boilers is maintained by a ‘filling loop’, which connects to your cold water pipe.
There are two main causes for low boiler pressure, which are:
These are not the only reasons your boiler pressure might be low so if you can’t find a leak and you haven’t been bleeding your radiators recently then consult a qualified engineer.
Whether you have an oil or gas, system or combi boiler, pressure loss is usually directly related to a leak. 99% of the time, a boiler losing pressure is a leak. Unless the dial sits at 0 even when topped up there’s a leak somewhere, even if you can’t see it.
Pressure Relief Valve is Faulty : Boilers will normally operate at 1.0 bar – 1.5 bar but they can reach 3 bar if there is a problem. A pressure release valve notices this abnormal change in system pressure and releases it. If the PRV has failed, it will cause the boiler to lose pressure.
Auto Air Vent Leaks : Central heating systems can collect air pockets over time. Bleeding the radiators is the best solution, but the auto air vent which is normally inside the boiler casing on newer combi boilers can also help to combat this problem but if the auto air vent is faulty, it could be losing pressure.
Leaking Radiators, Towel Rails and Radiator Valves are Leaking : The smallest of leaks with radiators can cause your system to lose pressure. This is the most common cause low boiler pressure. Check all your radiators, radiator valves and towel rails and see if there is any sign of water leaking. A small weep on a radiator valve is enough to cause low pressure on your boiler. If any of the connections are very loose, carefully tightened them up, this will usually solve the issue.
Radiators Are Full of Air : If you’ve recently had work carried out to your central heating system, it may have collected some air in the radiators and towel rails. You can release this pressure by using a bleed key. To bleed radiators and towel rails, simply open the vent with the key slightly. You’ll start to here air hissing out, once the air stops water will start to drop out, now close the vent off. Do this to every single radiator and towel rail in the property. Remember if you are constantly removing air from the radiators the pressure will drop each time you bleed the radiators.
Expansion Vessel : A faulty expansion vessel can cause pressure loss in a boiler. If re-pressurising the expansion vessel doesn’t work, the vessel will need to be replaced to stop the boiler losing pressure.
Pressure Gauge is Faulty : There is a chance the pressure gauge on the front of the boiler is not reading correctly, it is unlikely but it has happened. This is quite dangerous, especially if you are constantly topping up the pressure. Turn off the boiler and contact a RGI Registered engineer straight away.
Normally on the front of the boiler you will find a water pressure gauge, it will either be a needle gauge or a digital gauge which will indicate high and low pressure warnings.
|Explanation||Pressure Bar Setting|
|0.5 Bar : If pressure is below 0.5 bar, water has been lost from the system and must be replaced.|
|1.0 Bar : When the radiators are cold this is normal pressure.|
|1.5 – 2.0 Bar : When the radiators are hot this is normal pressure.|
|2.7 or above Bar : If the pressure gauge on your boiler indicates high pressure (above 2.75 bar), then you may need to bleed a radiator to bring the level down to around 1.5 bar.|
There is many brands and types of boilers, so the boiler pressure systems will differ. The first thing to do is to check the boiler manual and see if you can re-pressurise the system yourself. Your boiler may have instructions on the rear of the control panel. Please note that if you need tools to remove the panel on a gas boiler, don’t touch it. Call a RGI Registered Engineer to do this.
After following these steps, you should be left with a re-pressurised boiler but If you are in any doubt about how to re-pressurise your boiler system, or you have already done so according to the user manual but are continuing to have pressure problems, please contact our expert RGI Registered engineers and we will diagnose and fix the problem.