Nightmare time with Worcester Bosch repairs

[Cazza]

Hi

Was wandering if anyone can tell me if a competent boiler repair man should be able to detect a leak on an isolation valve to the boiler fairly easily. Worcester Bosch repair men came out 10 weeks ago to repair what was a leaking left flow unit. They also took boiler apart and replaced a few other things just in case that could leak (prv and expansion vessel). To cut a long story short I've had continuing pressure loss since they came out, one bar every 2 weeks. They kept telling me it couldn't be the boiler but I kept running isolation tests which proved to be the boiler. In all they've come out 7 times and 4 times there has been a leak on the left and right isolation valves. They tried tightening one, then replacing both washers, then replacing the right valve and now hopefully they are coming back to replace the left valve which still looks to be leaking.
Their attitude has been horrible, they are now unwilling to come out again they said if there is a continuing pressure loss after their visit today. I've had this worry for 10 weeks, had to run 4 isolation tests, had to take 8 days off work for their all day appointments getting up very early. I don't think I should have had to go through this. They kept telling me I had practically a new boiler so not to worry about the pressure drop. I think they should have ran some sort of isolation test on the second visit to determine where the leak was and properly diagnose it first (on the second visit they actually put in a new heat exchanger instead of finding the valve leak). Can any competent boiler repair man tell me what they think please?

 

[Cazza]

I will open all the radiators but I didn't want to put the pressure back up to 2 bar as by doing this aren't I adding air back into the boiler (which I would have just taken 2 weeks to let vent)? This would give a false pressure drop reading. I was just going to test it with 0.9 bar pressure.

 

[johnduffell]

around 50 litres is going to show a much bigger pressure loss with a cup full of water compared to a 10 rad system running at 100 litres

That's not true as water is incompressible for all practical purposes. The only bit that can expand when water is lost is the air in the expansion vessel.

I've had a system where the combi was in the loft in a bungalow, and bleeding a cup full of water out a radiator was enough to drop the pressure to nearly zero. So in my opinion, depending on the size of OPs system, yes a few drops from the isolation valves at the boiler is enough over a week, to drop 0.2bar of pressure.

That will have been a specific case where the expansion vessel no longer had any water in it. At the moment when the last water leaves the ev, the ev is full of air, so the air pressure has no effect on the system. This means the pressure on the boiler is the static head of water above the boiler. Which would be practically zero if the boiler is at the top of the system.

If the air in the ev was unconstrained, the pressure would carry on dropping smoothly.
Hope that is useful, even though irrelevant to the op.

 

[John.g]

I will open all the radiators but I didn't want to put the pressure back up to 2 bar as by doing this aren't I adding air back into the boiler (which I would have just taken 2 weeks to let vent)? This would give a false pressure drop reading. I was just going to test it with 0.9 bar pressure.

Just to be sure that we are talking about the same thing, pre pressure is the pressure at the air end of the E.vessel when its unconnected at the other (water) end, the filling (or test) pressure in your case is the pressure as shown at the boiler panel, you say you have a pre pressure of 1 bar, so if you just pressurised the system until exactly 1 bar then you will have no water (reserve) whatsoever in the E.vessel and theoretically if you drained a eggcup full of water from the system then that pressure will fall to 0, so how are you proposing to test the boiler at 0.9 bar?.
As stated above, assuming a prepressure of 1bar, a filling pressure of 2 bar will give you 2.67 litres of water (reserve) in the E.vessel, you will have 2.18 litres remaining when/if pressure falls to 1.75bar, 1.6 lires @ 1.5bar, 0.89 litre @ 1.25bar and 0 litres @ =or< 1.0 bar.

 

[Cazza]

Thanks John. I thought a Bosch guy said to me the gauge on the front of the boiler is showing you the water pressure, that the 1 bar pressure of air in the expansion vessel you can only measure with a meter connected to the expansion vessel. So I was thinking the two are separate and the gauge just measured the water sat in the heat exchanger part of the boiler. If I add water to the system until its 2 bar then I am adding air into the heat exchanger as well as water which will auto air vent and drop the pressure. I thought water only goes into the expansion vessel as the heat exchanger heats and expands the water, giving it somewhere to go.

 

[John.g]

The E.vessel contains a rubber "bladder" (called a diaphragm) like a heavy duty baloon, this is pumped up with air to whatever pressure is required, ie 0.5 bar to 1.0 bar depending on the E.vessel duty. The diaphragm will then be resting hard up against the opposite end of the E.vessel where the water connection is attached so in this state will contain 8 litres of air or whatever its capacity is.
You then open the filling valve and no water will be admitted to the E.vessel until the water side pressure is > than the prepressure, in your case (if it has been pumped up properly) 1 bar, the E.vessel will contain a certain amount of water based on this differential pressure and will compress the air on the opposite side of the bladder. Again in your case a 8 litre E.vessel with 1 bar prepressure and 2 bar filling pressure will contain 2.67 litres of water. As the boiler/system water heats up then the expanded water will be forced into the E.vessel and add to the existing 2.67 litres and the E.vessel (+boiler) pressure will rise further. There is no mixing of water and air in the E.vessel.

 

[Cazza]

Thanks for your reply John. I am still not sure what the gauge on the combi boiler is showing me exactly. Is it just the water pressure or boiler pressure (i.e. air in the expansion vessel plus the water pressure in heat exchanger and expansion vessel) ? Or is it just measuring the expansion vessel pressure water ?

 

[johnduffell]

Just to pick up where the other John left off, under normal working conditions the two will be identical. It's only setting the initial charge that it needs to be only air in there. Once your charge is set correctly and confirmed correct, you only need to worry about the overall system pressure.
The guage measures the water pressure though, hence when when the ev becomes empty it no longer reads the air pressure.

 

[Cazza]

So if the boiler gauge is only reading the water pressure and I'm doing an isolation test with the boiler off (so no water going into the ev) then I should be able to start the test with 0.9 bar water pressure

 

[Riley]

I am not being rude but this is getting needlessly complicated

 

[Cazza]

Can you not just answer my question Riley?

 

[Riley]

Yes I’ll happily give more free advice!! Seriously, remember people are giving their time here for nothing. Again I’m not being rude Cazza, this thread has leapt from one extreme to the other originally you were complaining about WB, then you were going to contact the CEO, which were it me I’d still do irrespective of whether they’ve fixed it this time or not because of appalling customer service. Now we have got to the fine tuning of a boiler which you can’t do and the chaps giving advice above should really know better as you can’t take your boiler case off as you’re not Gas Safe.

Quite simply you either have a leak or not. Leave it the two weeks you said you would and see if it’s lost pressure. As said above let the system be completely cold before setting your pressure then just monitor it. You haven't even given this latest fix a chance yet. If they have replaced the two valves on the boiler then I’d be very surprised if they are not shutting off properly for potential future isolation tests.

Ultimately this comes down to what you sort with WB as I still feel that the buck stops with them. But if they wash their hands of it then enlist a local recommended engineer to come in and look for you and build a rapport don’t go on the attack with him. Sometimes finding a leak requires a couple of visits, it’s not always incompetence

 

[Cazza]

I know people are giving their time and I thanked everyone in one of my last posts and said I wanted to leave it 2 weeks. But then John came back saying it won't work. So now I am just trying to understand why that is. Thats all Riley! No need to patronise me or say I am ungrateful. I take offense you are saying to me not to go on the attack with a new engineer. I was extremely patient with all the 8 Bosch visits to my property always being polite and offering many cups of coffee and tea. Never once raised my voice or criticised. Yet I do feel I was unfairly treated by them.
Like I keep saying I can't top it up to 2 bar because that is putting AIR into the boiler which will give a false reading.
I thank again all the people trying to help me on this forum and its a shame some people's motive for helping seems to belittle and put others down (as often happens on internet forums just to make themselves feel better because they are having a bad day)

 

[John.g]

So if the boiler gauge is only reading the water pressure and I'm doing an isolation test with the boiler off (so no water going into the ev) then I should be able to start the test with 0.9 bar water pressure

So if the boiler gauge is only reading the water pressure and I'm doing an isolation test with the boiler off (so no water going into the ev) then I should be able to start the test with 0.9 bar water pressure

So if the boiler gauge is only reading the water pressure and I'm doing an isolation test with the boiler off (so no water going into the ev) then I should be able to start the test with 0.9 bar water pressure

Because water is incompressible then if you do the test at 0.9bar, the pressure should drop to 0 as soon as the tiniest amount of water leaks or is released. In practice, there is all ways some small amounts of air entrained in the water so this will act as a sort of E.vessel in itself, the point is that you will have no idea what amount of air is entrained so the pressure may drop to zero very rapidly or very slowly. That is why it is advisable to pressurise higher than the pre pressure as air is compressible and you can get a accurate feel (time wise) for any drop in pressure as the amount of water released will be exactly the same each time.
OK, if you pressurise only to 0.9 bar and you then have NO subsequent fall off in pressure then it would be hard to argue that there is any leak present.

 

[Riley]

Right I’m out. A leak is a leak. There’s no more benefit putting 2 bar in as there is 1.5 it’s maths. If it drops you have a leak. You have an automatic air vent on the boiler to deal with air. If the Ev is set correctly then you shouldn’t have issue there either.

Just FYI I wasn’t patronising. It’s very easy to vent into the guy coming in to fix someone else’s cock up. Was just giving you a heads up. But as you seem to think it’s now our fault you can’t get it sorted then I wish you luck

 

[Cazza]

Riley I never said it was anyone's fault on this forum.

Many thanks for explaining John. The pressure gauge hasn't dropped from 1.3 bar since Saturday morning (even with a firm flick). So i'm hoping replacement of the leaking valves has done the trick.

 

[SimonG]

Is this still ongoing?

I'm sure that a visit from a competent engineer would have had you sorted.

 

[sammathias]

How is topping up pressure to two bar adding a load of air into system. Please explain?

 

[Cazza]

UPDATE: The boiler gauge has still lost pressure from 1.5 bar to 1.2 bar within exactly a week. So I've decided to write to Martyn Bridges, top technical person at Worcester Bosch with all that's happened. I will let you know IF I hear back.

 

[John.g]

Not sure if this is with the boiler isolated or not for the week?. One way or the other the boiler or boiler/system is after losing almost 0.9 litres of water or else air is still being released through the boiler auto air vent.

 

[Cazza]

Hi. No not isolated, just normal. I've started an isolation test this morning. Not adding anymore water to it (1.2 bar start off) in case of adding back in any air. My gut feeling is it's not auto air venting, especially as i've got new lot of inhibitor in the system. The two new isolation valves don't appear to be leaking, so I think they fixed that. I have seen on google that if the pump setting is too high this can cause a pressure loss (something to do with cavitation don't really understand) so maybe its that I don't know if Worcester checked this.
It will be interesting to see, with the two new isolation valves, if there is any pressure loss whilst boiler isolated. But I wrote off to Marytn Bridges because like Bosch themselves told me it shouldn't be me still worrying about it, after Bosch found a pressure drop on the boiler gauge.

 

[sammathias]

Blah blah. Going around in circles and yet still don't listen to a word suggested.

 

[Cazza]

I've taken on board what everyone has said. Well I ran the isolation test for the last 24 hours and it dropped 0.15 bar at least. I've just taken 200 ml out of a radiator with it still isolated and it doesn't drop on the gauge. This is telling me its definately the boiler losing pressure. Whether that is because of air still venting 9 days later I don't know. But my guess is its still just going to keep on dropping as that's what its always done.
I wrote to Martyn Bridges but had an out of office reply that he is not back for 2.5 weeks. Just my luck.
I guess I will have to get out my own engineer and send the bill to Bosch because if there is a leak they've caused it?

 

[Cazza]

I've reversed the isolation test and i'm going to carry on giving it the obligatory two weeks, so if after the 18th April it keeps on dropping pressure then i'll know for sure its not just air venting and can update Mr Bridges with the information.

 

[Riley]

I've taken on board what everyone has said. Well I ran the isolation test for the last 24 hours and it dropped 0.15 bar at least. I've just taken 200 ml out of a radiator with it still isolated and it doesn't drop on the gauge. This is telling me its definately the boiler losing pressure. Whether that is because of air still venting 9 days later I don't know. But my guess is its still just going to keep on dropping as that's what its always done.
I wrote to Martyn Bridges but had an out of office reply that he is not back for 2.5 weeks. Just my luck.
I guess I will have to get out my own engineer and send the bill to Bosch because if there is a leak they've caused it?

I realise your frustration Cazza but seriously how have they caused it?? No one will set out to purposely cause an issue with your boiler. You do realise that there is a good chance that your boiler may just have had more than one issue. I went out to a WB the other day and there were three separate leaks on it. The third was an absolute nightmare to locate and I only found it because of a drip passing through the beam of my torch. Don’t be so aggressive and I’m sure you will get there. If you don’t then keep on at WB but I would not lead with them causing leaks as they will just not take you seriously. Be factual

 

[Cazza]

Well my conclusion is in the last 6 days it has not dropped (hardly anything anyway). Its now been over 2 weeks since WB last came. I've not had the heating on much. But if there was a leak it would have shown even switched off i'm guessing. When I put the heating on next winter if it starts losing pressure again then all I can think it is the pump setting is too high and causing air venting (would explain the vibration noise I get as well). So when I get it serviced next year I will ask them to check this and slow it down a bit. So i've no need to go back to WB. But I am glad I persevered with them and got them back out because on their very last visit they did fix the isolation valve leaks which needed to be done. I don't think my last post was aggressive, I even had a question mark as to question if they caused the leak. Anyway no point in arguing.
Thanks everyone for your thoughts, just glad I can leave it be now.