Pressure Dropping, but not completely

[pressuredrop]

Hi,

So I have Vaillant Ecotec Pro 24 boiler.

It was working fine for the 2 years I was living here and started to drop pressure when it was off - sitting at around 0.4 bar. Every now and then it would flag up a F22 and need refilling - twice in 6 months. Then as autumn rolled around it started to happen more frequently - it would take 3 weeks, then 2 weeks then 1 week, now it only takes a day to drop from 1.5 bar to 0.3/4. But it never drops to zero. Which was puzzling as if it a leak it surely must empty all the way to zero pressure?

Once it started to happen after 2 weeks I started to look for a leak - thankfully although i'm in a late 50s concrete tower block - the pipes are mostly external to the wall - only the ballroom pipes are boxed in mdf, the rest are out in the open. None of the pipes have wet spots under them, and the boxed in area isn't damp (and now it drops daily you would think there would be quite a bit of damp now!). Which again was puzzling.

As I started using the CH I noticed as it was on, the pressure would steadily rise till it 3bar and then dump it out the system. At this point the lightbulb above my head went off and figured the expansion vessel had gone flat. Considering the boiler hadn't had a service - I got it serviced, and the expansion vessel charged again, and was told that should probably fix it.

Unfortunately it hasn't, it's still dropping from 1.5 to 0.4 over 24hours. I've placed a bag over the pipe that goes outside - and it hasn't collected anything despite the boiler dropping pressure. I've also collected from the other pipe that leaves the boiler and heads to the main stack (See photo: is this the PRV? - it's the furtherest to right, white plastic pipe behind the copper one). This has collected a small amount of water over 6 hours today (probably about a quarter of a shot). If that is the PRV how can I check it? Anyone got any instructions for me to follow or how to replace? Or will it be a call to the plumber again?

If that's meant to do that, any idea what else it could be and how to diagnose? I haven't been able to find instructions on how to isolate the boiler in the vaillant manual. If anyone could offer any help to do that I could at least be able to determine whether the leak is in the boiler or in my system somewhere.

Any help appreciated.

Thanks,

A

 

[picasso]

The bad news is it looks like your heat exchanger has a pinhole in it, easiest way to confirm is to top up boiler and using a 4mm allen key close the isolating valves under the boiler, don't use the boiler for 24hrs and if the pressure drops its the heat exchanger.

 

[pressuredrop]

Ah ok. Thanks.

Where do I find the isolating valves? And what do I have to do to the boiler beforehand? - I'm guessing turn it off? Any rough idea how much it would cost if it is the exchanger?

 

[oph]

Ah ok. Thanks.

Where do I find the isolating valves?

Those X2 brass valves attached to the x2 outer 22mm pipes either side.

4mm allen key required..................

 

[picasso]

Depending on how old it is it might be more cost effective to replace the whole boiler. Did I mention the 4mm allen key ?

 

[pressuredrop]

really? that bad it's only 5 years old.

I have a 4mm allen key. So I close (from left to right) the first pipe on the left and then the 5th pipe?

 

[picasso]

With these long warranties it might be worth checking its not still covered .

 

[pressuredrop]

Ok. This may sound like a stupid question, but how am I meant to know the valve is shut? And conversely how am I meant to know the valve is open again when I turn them the other way tomorrow?

 

[picasso]

If you look at the valve it will only turn one way and it will only go so far, then tomorrow turn them back to where you started.

 

[lightning]

Get Vaillant out on a fix price repair

 

[picasso]

You really think vaillant are going to change a main heat exchanger on fpr ?

 

[hertsboilers]

The bad news is it looks like your heat exchanger has a pinhole in it, easiest way to confirm is to top up boiler and using a 4mm allen key close the isolating valves under the boiler, don't use the boiler for 24hrs and if the pressure drops its the heat exchanger.

Hi @picasso , one case in last week, a Vaillant ecoTEC MK1 system boiler installed in a loft space, it need top up on a daily basis. I made total three visits, ie, isolated the boiler from the rest, of course the system wasn't running, surprised me there were no leaking on both sides. So restored the system, again, once heating is on, it lost its pressure at the same rate again. I suspected it is the main heat exchanger having crack(s) only appearing when combustion is on.

Advised Vaillant fixed price repair, which is booked next week. We will see if Vaillant will replace this main hex by their FPR.

 

[lightning]

Yes as they have done it for a couple of my customers

 

[picasso]

I remember seeing a list of what they would repair on fpr and the heat ex was not on it, maybe they have changed over the last few years.

 

[hertsboilers]

I remember seeing a list of what they would repair on fpr and the heat ex was not on it, maybe they have changed over the last few years.

I will let you know in next week.