Vaillant Ecotec Plus 831 losing pressure overnight

[Boiler]

Hi all,

I'm having problems with my boiler and am hoping someone can offer me advice. Few days ago our heating and hot water stopped and on inspecting the boiler I was met with the F.75 error. We had a plumber come out and the first thing he asked was if I had the owners manual which didn't fill me with confidence. Anyway, I didn't have one as we recently moved in so the plumber tried refilling the system to bring it up to 1.4/1.5 as he said this what Vaillant's were supposed to be at. It got it working which was great until yesterday morning when we lost heating and hot water again. As I had watched what he had done, I refilled it and again this morning the pressure had dropped.

Now before I call a plumber out again, I want to try and narrow the issue. I have been searching and found that it could be a number of things but I want to try and establish if it's a leak in the system or if it's a problem with the boiler. Is it possible for a DIY'er to do this? I have checked the visible areas around the radiators for a leak but can't see any signs of one (assuming that going from 1.5 to 0.9 in less than 24 hours would mean a reasonable size leak!). Also, there are a few "valves" with screw slots underneath and one was at 45 degrees. Should all the valves be closed? If not, which ones should be open and which should be closed?

Any help/advice appreciated.

Thanks. 🙂

 

[TBServices]

Hi all,

I'm having problems with my boiler and am hoping someone can offer me advice. Few days ago our heating and hot water stopped and on inspecting the boiler I was met with the F.75 error. We had a plumber come out and the first thing he asked was if I had the owners manual which didn't fill me with confidence. Anyway, I didn't have one as we recently moved in so the plumber tried refilling the system to bring it up to 1.4/1.5 as he said this what Vaillant's were supposed to be at. It got it working which was great until yesterday morning when we lost heating and hot water again. As I had watched what he had done, I refilled it and again this morning the pressure had dropped.

Now before I call a plumber out again, I want to try and narrow the issue. I have been searching and found that it could be a number of things but I want to try and establish if it's a leak in the system or if it's a problem with the boiler. Is it possible for a DIY'er to do this? I have checked the visible areas around the radiators for a leak but can't see any signs of one (assuming that going from 1.5 to 0.9 in less than 24 hours would mean a reasonable size leak!). Also, there are a few "valves" with screw slots underneath and one was at 45 degrees. Should all the valves be closed? If not, which ones should be open and which should be closed?

Any help/advice appreciated.

Thanks. 🙂

Get a different engineer if you don't trust the one you have. I'd be looking at filling loop and expansion vessel with a drop that big.

 

[Boiler]

I will be calling someone else, someone who's knows the Vaillant like the back of his greasy hand! 🙂 With a drop that big, are you saying it's more likely to be the boiler at fault? If that's the case then it's a slight relief as I don't fancy having to gut the flooring to redo the pipework!

 

[TBServices]

I will be calling someone else, someone who's knows the Vaillant like the back of his greasy hand! 🙂 With a drop that big, are you saying it's more likely to be the boiler at fault? If that's the case then it's a slight relief as I don't fancy having to gut the flooring to redo the pipework!

How old is the boiler?

To lose pressure that quickly, you either have

a. A big leak that suddenly sprang out of nowhere, or
b. a pressure increase resulting in a PRV operating.

 

[kay-jay]

Tbh asking for the manual isn't necessarily a bad sign as all boilers have different fault codes and no engineer can be expected to know them all off top of his head.

Agree with comments about prv and leaks.

Sent from my GT-I9100 using Tapatalk 2

 

[TBServices]

Tbh asking for the manual isn't necessarily a bad sign as all boilers have different fault codes and no engineer can be expected to know them all off top of his head.

Agree with comments about prv and leaks.

Sent from my GT-I9100 using Tapatalk 2

Agreed. Always ask for a manual unless I have my ipad handy.

 

[Boiler]

How old is the boiler?

To lose pressure that quickly, you either have

a. A big leak that suddenly sprang out of nowhere, or
b. a pressure increase resulting in a PRV operating.

I believe it was installed in 2007/2008. We've been here 6 months and haven't had any problems until few days ago. What does b. mean? Would you mind elaborating?

 

[REDSAW]

Tbh asking for the manual isn't necessarily a bad sign as all boilers have different fault codes and no engineer can be expected to know them all off top of his head.

Agree with comments about prv and leaks.

Sent from my GT-I9100 using Tapatalk 2

best not call me either because first job is 'the installation manual' i dont like guessing too much.
rather, i like guessing then checking first.
bet the prv's passing.

 

[Boiler]

I guess it was a good sign that he asked for the manual. I did offer to bring it up on my iPad but he said he would check the basics first.

 

[rawr]

I would say exp vessel. from here at my computer. guessing

 

[TBServices]

I believe it was installed in 2007/2008. We've been here 6 months and haven't had any problems until few days ago. What does b. mean? Would you mind elaborating?

Can't elaborate too much in case you try to do a DIY fix and blow yourself up.

 

[Boiler]

Can't elaborate too much in case you try to do a DIY fix and blow yourself up.

I must admit, I'm a keen DIY'er and will try my hand at most things but anything gas related is where I draw the line.

 

[Boiler]

Is there a way of "isolating" the boiler from the rest of the system to see if it still drops in pressure? I mean without fiddling with the internals or disconnecting pipes etc

 

[rawr]

there is

 

[Boiler]

there is

But are you also worried I may blow myself up? 🙂

 

[rawr]

haha I know you won't, but you might

 

[Ian400]

Try this site to download vaillant manuals, [DLMURL="http://www.vaillantdownloadservice.co.uk/Pages/Default.aspx"]Vaillant Technical Download Service[/DLMURL]
Find the Isolating Valves on the Flow and Return pipes under the boiler, turn them Off, and leave overnight to see if it makes any difference to pressure loss. ( don't use the central heating during this time ).
You can check the PRV ( Pressure Relief Valve ) is letting by, by looking for the pipe which goes from the boiler through to the outside.

 

[novicegas]

Use the right size Allen key to turn the flow and return isolation valves off or you'll find you rip and damage them using a slotty. Prv can be easily checked. A vaillant savvy engineer will be able to cycle back through the faults on a three year old v combi, might be able to detect some other previous fault that might shed some light on this one. Any pipes on ground floor that might be letting by, under screed or floor boards, fernox leak sealer will only deal with small weeps not drops of your like.

 

[lame plumber]

if you say that the boiler runs ok when pressurised but loses pressure overnight, probably what's happening is the expn vessel has failed and this means when the boiler runs, there's nowhere for the hw to expand and the prv operates until 3 bar is established, then everything is tickety until the heating goes off, water cools, pressure drops and next morning boiler wont work due to low system pressure. So ask engineer to check expn vessel first before looking at prv and other leak possibilities.

from memory doesn't gsr state you shouldn't work on a gas appliance without access to the mfis

 

[stevetheplumber]

we are not actually supposed to work on any appliance with out the manufacturers instructions present a lot of engineers will have a laptop with them onyears ago we had a plate on the boiler which told us everything we needed to know now the plate would need to be as big as the boiler