Things that are annoying - taxes and having to take a cold shower in the morning right?
Low water pressure is one of the most common causes of a boiler not working, and whether it’s a F22 on a Vaillant boiler or F2 on a Viessmann boiler the result is aways the same. A chilly house, and an even colder.
Before we jump in and start to look at some of the fixes for this issue, lets first take a look at why some boilers are pressurised.
Pressurised systems have become more and more popular especially with condensing boilers. Rather than having cold feed and expansion tanks in the loft, the heating system is ‘sealed’ meaning once the water goes in, theres no way out. In a research paper in 2016 Flamco listed the main advantages of a sealed system as being -
· No water loss in the system due to evaporation.
· Leaks directly affect the system pressure and are more readily identified.
· Reduced risk of freezing due to no exposed pipework above the insulation layer.
· Flexible installation options, removing the need for high level expansion tanks.
· Using circulation pumps with a larger pump head is no problem, this makes it possible to use smaller diameters of pipework.
· The overpessure prevents boiling sounds in the system at higher temperatures.
· Air is prevented from being reintroduced to the water, reducing corrosion and improving thermal efficiency.
We believe the last point is the most important. As the system is sealed, air is therefore prevented from entering the system and as such, this reduces the amount of oxygen in the water, which in turn reduces the chances of system corrosion. There are lots of different ideas on preventing system corrosion and the importance of considering this as a factor during the installation stage but we’ll save that for another blog post.
So we have our sealed system, why have I lost water pressure?
There can be a number of reasons but they are all linked to the same outcome – pressure has been allowed out of the system.
The first thing to do is have a look around the system to see if you have any leaks. It is common for a small leak to evaporate and over time the pressure will slowly drop, these can be more difficult too located but there will be tell tale signs such as a stain on carpets under radiator valves.
If you have established there are no leaks, then you can proceed to topping up the water pressure, this is carried out using a filling loop. All boilers are similar in this process however some boilers such as Worcester and Ideal have a built in filling loop. Following the process below will allow you to top the system pressure up, resetting the boiler will re-establish the heating and hot water.
If you have persistent issues with low pressure it is important to have a Gas Safe registered engineer take a look at your system. Introducing fresh oxygenated water in to the heating on a regular basis can have a negative effect on the system and speed up the corrosion process resulting in blocked pipes, cold spots on radiators and even blocked heat exchangers.
You will see from the pressure gauge that the pressure is low. Boilers are generally designed to cut out below 0.5 bar and this is usually shown by a red section ( 0.5-3 in green) on the pressure gauge.
Common Fault Codes for Low Pressure –
Vaillant F22
Worcester – on screen display or alternating blue flashes
Viessmann –F2 – Although this is a ‘burner blocking’ code and can point to other issues
Ideal F1
Glowworm F22
Baxi E119
Potterton E118
Vokera A04, AL40 or AL41 depending on model
Ariston 108
