Central Heating Pressure Problem

[DazJWood]

I am having a slightly weird problem!

I had a Vaillliant boiler fitted October of last year and the central heating and hot water has been working fine.

I came home yesterday to find an BMT error on my wireless Thermostat so went up to the loft to check the boiler. The pressure guage was showing nothing and 0.1 flashing up on the display.

I walked round all the radiators looking for signs of a leak and there was nothing to be found. I checked the drain off valve outside and this was shut off with no signs of water leakage.

The only other thing that has been changed was permanently capping off the pipes that feed to my bathroom as I'm currently redoing it and the radiator will be relocated. This was capped off before Christmas back into the adjacent room and I had the room's flooring up for sometime before putting it all back down. Even if it there was a leak then I would see water coming through the ceiling in the lounge below or at least evidence of water damage on the ceiling.

I phoned my mate who's is a plumber and he was a little puzzled and said maybe it was an air pocket that had been in the pipes that had moved over time and suggested refilling it back up and monitoring it and also to recheck the drain off valve in case it was leaking. I refilled the system and had the heating on for a number of hours. I also wrapped and taped a plastic bag round the drain off valve so I could see if it was leaking when I got back to work today.

Well when I got back today the heating was back to the same condition with no pressure. I've checked all the radiators again and there's no signs of water. I've checked the drain off valve and no signs of a leak.

On suggestion from my mate I've checked the pipe that comes from the boiler down the outside of the house to ground level and it's bone dry inside. The pressure vent pipe or whatever doesn't appear to have been expelling water either from what I can see, though it's a bit dark to be absolutely sure.

I've just refilled the system back up and bled the radiators but have a strong suspiscion that when I come back home tomorrow it will be once again at a low pressure.

I am puzzled as anything as I don't know where the water is going, can see no evidence of where it is going and am really not sure what to do next to resolve it.

Has anyone any ideas?

Thanks in advance,

Daz

 

[Transcoman]

Daz, you say the hot water is working fine too but when the boiler was fitted, did you keep the same hot water cylinder?

This may seem a long shot, but l had a similar problem when l installed a new system boiler but the owner didn't want to replace his 30 year old hot water cylinder. Every day for three days running the system pressure dropped to zero yet there were no signs of a leak anywhere. But the when l refilled the system for a third time l could hear water filling inside the cylinder and it dawned on me what the problem was; so l drained down the system, capped off the primary flow and return, refilled the system and the problem was clearly shown as being a perforated indirect coil in the hot water cylinder.

A new indirect cylinder was fitted and the problem cured. I'd suggest getting your plumber to try the same, at least that way you can find out first before buying a new cylinder.

 

[LIFES A GAS]

Have to agree with "Transcman" if you have a system boiler, if your Vaillant is a combi or system type the problem could be the main heat exchanger leaking via the condense waste. You can check this on the R1 models by pulling off the rubber connection on the bottom of the boilers heat exchanger, with the boiler turned off there should not be any water dripping from the connection, if nessesary pressurise the system to above 2 bars when checking for this.
Hope this is helpful as it would be a warrenty issue. Martin.

Me again, I forgot to say: if you have a cylinder then turn off the gate valve that is between the storage tank and your cylinder, if the coil in it has failed the only route that the water could take is via the open vent pipe work ( the one that loops over the top of the cold tank) if water drips from it when the boiler is off (over night) then I would say its the coil that has failed,hang a can over the end to see if that is where your water is going, this is a much easier way of checking than disconnecting the pipe work to the cylinder.
Good luck, Martin.

 

[DazJWood]

Thanks very much for the replies.

I've now found out that it was actually a leak. One of the radiators pipes has a very small pinhole on the solder joint that was spraying up against a polystyrene box of floor tiles that I had left in front. It was dripping down the side of this and down onto the carpet underneath the box and then through to the floorboards below.

I appreciate your time in replying,

Daz

 

[Transcoman]

Thanks very much for the replies.

I've now found out that it was actually a leak. One of the radiators pipes has a very small pinhole on the solder joint that was spraying up against a polystyrene box of floor tiles that I had left in front. It was dripping down the side of this and down onto the carpet underneath the box and then through to the floorboards below.

I appreciate your time in replying,

Daz

Nice one Daz, at least you found the cause.

 

[kristy22]

Have to agree with "Transcman" if you have a system boiler, if your Vaillant is a combi or system type the problem could be the main heat exchanger leaking via the condense waste. You can check this on the R1 models by pulling off the rubber connection on the bottom of the boilers heat exchanger, with the boiler turned off there should not be any water dripping from the connection, if nessesary pressurise the system to above 2 bars when checking for this.
Hope this is helpful as it would be a warrenty issue. Martin.

Me again, I forgot to say: if you have a cylinder then turn off the gate valve that is between the storage tank and your cylinder, if the coil in it has failed the only route that the water could take is via the open vent pipe work ( the one that loops over the top of the cold tank) if water drips from it when the boiler is off (over night) then I would say its the coil that has failed,hang a can over the end to see if that is where your water is going, this is a much easier way of checking than disconnecting the pipe work to the cylinder.
Good luck, Martin.

I have a similar problem. New Valiant boiler, some new rads, loft conversion and loss of pressure in pressure vessel in loft. Who to get in touch with? Valiant, heating engineer. Pleased to have any suggestions. I submitted this prob to Plumber's forum, central heating. I am Kristy22. Appreciate and advice.