I'm sorry if this sounds patronising, but do you have the manual? If not you can download a copy from the following:-
www.bhl.co.uk/.../Vaillant%20EcoTec%20Plus%20Open%20Vent%20Installation%20...
The fault code F22 is cited as:-
F.22 Dry fire. Too little water in the appliance, water pressure sensor defective, cable to pump or water sensor defective, pump blocked or defective, pump output too low
The likely cause is that you need more water in the system to increase the pressure, but bear in mind that there might be another cause for the fault code showing.
As has been stated, the Vaillant ecotec plus has two taps to fill the (sealed) system. Both have to be opened. The reason for this is that it is a legal requirement for the water to be isolated from the mains water supply. There should also be a one-way valve to prevent back pressure from contaminating the water supply.
As the taps are quarter turn taps, then you should be able to turn them more than 45 degrees. If you can't then don't force them, or you may cause a lot more damage and end up with water everywhere. Are you sure you're turning the correct taps? Unfortunately, the manual doesn't show the position of these taps and it has been a few years since I fitted one of these, so I can't recall the exact positions - are there any labels indicating the name of the inlet pipes? If so, then look for something like water mains inlet and heating system inlet. There should be taps on each. Maybe even a link between the two pipes? You might even see the one-way valve (most of them are about 2-3 inches long with an arrow on one side to indicate direction of water flow).
The other issue that you need to consider is why the pressure is low. Have you changed any radiators recently? Or had any leaks? Is it a new system, so that you are bleeding out trapped air? If it's just developed the fault and has been okay for a long time, then you might have to investigate further to determine the cause of the problem.
I would advise not leaving it, as I saw one case where a leak had started in a joint in a pipe running through a wall in a kitchen. It wasn't obvious. The wall got soaked over a long time at the back of cupboards and destroyed the plaster and the kitchen cupboards - resulting in a lot of drying out, replastering and a new kitchen. The plumbing work to repair the joint wasn't significant, but it turned out to be a very expensive leak!
If you know the cause of the problem then fix it as soon as possible. You don't want to lose the heating system over winter. If the warranty is still valid then make sure it is repaired because it can invalidate the warranty if the suppliers find out you knew there was a fault and you didn't have it seen to.
I don't want to frighten you, but boiler breakdowns can be very expensive, so the rule is to get it seen to asap. It might seem to be an unnecessary expense now, but I've been out to many boilers where the owner didn't bother with even standard maintenance. The eventual cost and inconvenience was incredible. As you have a top of the range boiler, it's best to look after it.
Preaching over.
Hope you get it all sorted out satisfactorily.
Glass, July 2009
