Vaillant Combi condesing boiler losing pressure daily no sign of leak

Lady_K

I have a Vaillant ecotec plus 824 combination condensing boiler, its been in 4 years in December.

Its losing pressure f22 so much that when I top it up in the morning with the 2 keys underneath (left says open/closed right says water) it will start then but will not last long enough to restart the heating for the next morning but that also includes me topping it up again before bed even though it hasnt gone to f22 again but the pressure bar is just in the grey area. I did this to see if it would be enough to keep it going to start the next morning but its not.

There is no visible signs of any leaking coming from anywhere unless I havent found it, this is a problem that has got worse and worse and the topping up has got closer together but I'm concerned that its getting to winter now.

During the summer when the heating wasnt being used I did not have to top it up although before this when heating was in use it was every 2 days.

I am not sure if the sound from it has changed slightly when the water is in use sometimes it gives a trickling sound. Is there any way water might be escaping back again through the boiler somehow? Should I check outside and if so how should I and where?

I'm hoping to find out where to save a plumber having to go ripping up all the floors again as finding a leak anywhere in the system is going to be a nightmare

I have also found that if I top it up to the midway mark that is suggested once the heating is on it goes right into the red area and the screen flashes BAR. sO when I top it up I have to do it less than halfway, in fact only just into that area or it will go into the red

bambibashercol

When you run the heating does the pressure gauge rise quickly and go above 3 bar?
If so the expansion vessel needs recharging or replacing.
If this is ok then fill your system to 1.5 bar and then isolate the valves under the boiler on the flow and return. leave overnight and check for pressure drop next morning.If its dropping pressure then this would point to the water leaking back into the heat exchanger.

Lady_K

bambibashercol wrote: »

When you run the heating does the pressure gauge rise quickly and go above 3 bar?
If so the expansion vessel needs recharging or replacing.
If this is ok then fill your system to 1.5 bar and then isolate the valves under the boiler on the flow and return. leave overnight and check for pressure drop next morning.If its dropping pressure then this would point to the water leaking back into the heat exchanger.

I will go check it now, I havent topped it up this morning yet so I know it will be showing the f22 when I go to it. But from what I remember it does rise quickly within a few minutes if I top it up to the middle of the middle bar thing which is where they tell you to top it to so I do have to only top it up to where its only just in that area in order for it not to rise into the red area

Sorry about not being too clear on the bar numbers I will check those too. If it is the expansion vessel will this be an expensive job and would it explain the trickle sound I hear? Is it worth me checking outside?

bambibashercol

ok its your expansion vessel if its leaking outside. It may just need recharging and this can be done with a footpump.

Lady_K

I have just been to look at it and it was showing f75, it does do this sometimes too so I had to top it up then turn it off at the switch to restart it. Water worked straight away but the heating did not come on straight away even though it was set to, usually it just starts up after topping up. I had to switch the wireless control back to off then auto again and heating started.

I looked at the bar dial, there are no numbers on but just sections, light grey area, mid grey area, red area. I topped it to to the middle of mid grey area which is what they say to do it to in the diagram. Within 6 minutes it went into the middle of the red area then I switched the heating off because if I didnt it would have gone right to the top end of the red area and start to flash as it has done before. When this has happened before I have to leave the heating off for a while the test it again by turning the heating back on to see if its dropped down safely enough to stay in the mid grey area, if its still going into the red flashing bar I have to turn it off again and just keep trying that untill its safe to have the heating on again.

I havent checked outside yet should I do this and if so when the heating is on? and where exactly should I look for water coming from?

bambibashercol

confirmed it's your expannsion vessel. It can be repressurised with a foot pump.

Lady_K

Is that possible to be done diy? I have no clue where the expansion pump is,
I don't have a footpump apart from a camping one is this ok and is it easy to do?

bambibashercol

No you will not do it with a camping foot pump.
It has a valve on top of the expansion vessel like a car tyre valve. It needs pumping up to about 1 bar. After you have done this if you still have problems then it a split in the diaphram.
You can either replace the expansion vessel or fit a second expansion vessel somewhere on the system. Its not really a diy job if the expanssion vessel needs changing.

EliteHeat

If you find water coming out of the valve of the expansion vessel, then the diaphragm is definitely split as Bambibashercol said. If this is the case do not waste you time trying to re-pressurise it.

A temporary solution to the problem is to half empty your least useful radiator and then re-pressurise the system. Do not bleed this radiator, it will act as an EV, but will obviously not give you full heat.

Lady_K

All this is above me and I don't have a pump anyway. I will most likely have to get a plumber out to do it, are most of them familiar with these vaillant combi condensing boilers how? as I had a vaillant before this one and it was almost impossible to get a plumber that knew anything about it.

Is the expansion tank easy to find once the door is open? What kind of pump is needed and where would I get one from please?

EliteHeat

The expansion vessel is at the rear of the boiler, it is big and red (or possibly grey on yours) and you cannot really miss it.

At the top of the vessel is a plastic dust cap like you have on your car tyres. Take this off and there will be a normal valve underneath, again just like on a car. If you depress the centre either air or water will come out. If it is water, the vessel is shot.

You will probably need to remove the outer case. It is secured by a big, cross-head screw at the bottom of the boiler. Isolate the power to the boiler before removing it.

This is not a job for a plumber, it is a job for a registered heating engineer, but don't pay anyone to do this simple check - it is very easy.

If you do not already have them, you can download the installation details from Vaillants website, these will explain how to remove the case and you will see an exploded view of the boiler showing the expansion vessel.