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]

Yes this is true and must affect their ability to be thorough. The crazy thing is because of their system of trying to save time on visits and repeat visits end up actually spending more time and money in the long run. If they had spent more time diagnosing and finding the isolation valve leak they wouldn't have replaced a heat exchanger! Perhaps Bosch should allow their engineers more time on a job (a stitch in time saves nine). I did find though all the Bosch men that arrived in pairs spent a lot of the time chatting between themselves about personal stuff, rather than fully concentrating on the job.

 

[Millsy 82]

When my dad was in hospital the nurses talked about their holidays to each other, when I go to a shop all the staff chat to each other about personal stuff. Everybody speaks about personal stuff.

I charge a fixed price for diagnosis because on average I spend about 20 minutes on breakdowns but sometimes a leak is extremely difficult to find.

 

[John.g]

If you suspected a boiler leak then with the apparent view that isolation valves don't hold, its obviously going to take longer than 20 minutes if you have to start blanking off.

 

[Cazza]

I've been in hospital before and seen patients wanting nurse attention ignored because nurses were too busy chatting. But yes of course colleagues will chat to one another and they should, what I meant was they didn't seem that motivated to fully diagnose the pressure loss. I think the ideas given in this thread says the Bosch men could have done more, things like test the isolation valves for leaking or block the airvent and see if there was a pressure rise. But they just seemed to want to do the bare minimum as quickly as possible, not to come back and move onto the next client. Even shouting at me almost that they can't come out again and saying I could have my money back, rather than get to the bottom of the issue as they promised they would if the gauge showed a drop in pressure, which it did.

 

[sammathias]

If half of your radiators are 'turnt off' then how can you test for a pressure loss successful?

 

[Cazza]

Hi. I'm not an expert, I'm no plumber and don't understand why this would make a difference as there is still water sat in the pipes. All the radiator valves have been checked for leaks (about 5 times) and there aren't any. The pressure loss test carried out by Bosch with the large gauges was on a (so say) isolated boiler and also on the radiator system at the same time. So at least it shouldn't have made any difference to the boiler test?

 

[John.g]

No it shouldn't but with "proper" isolation and two pressure gauges it should differentiate between the two systems, with both gauges falling together it certainly points to isolation valve(s) passing but doesn't tell which system is leaking.

 

[Riley]

This to and fro is kind of going in circles. If the OP gets nowhere with WB following this latest fix and contacting CEO then they will need to enlist an independent. Simplest option would be cut two ISO’s into the F & R temporarily if the ISO’s on the boiler are suspect. By the sound of it they’ve been replaced so I’d be dubious as to their failed functionality so soon . If you already have a primary filter on the return then you could isolate there.

 

[Cazza]

I'm going to leave it now for 2 weeks, to allow air to vent. If it drops down as low as 0.9 bar (from 1.3) then I will run an isolation test. If it still drops, then with it still isolated I will drain 250 ml from a radiator and watch the gauge to test the new isolation valves. If no further drop then I will assume its the boiler.
If the isolation valves are leaking I will assume it is the pipes (as my boiler sits higher than the radiators being on 2nd floor; so where the last isolation test showed both boiler and radiator leak I doubt a boiler leak would have shown up as a radiator leak).
The previous isolation test was done with a new right isolation valve, and an old left isolation valve. Now both are new. So I can't rule out the previous test had an isolation valve leak.
Thanks for all your thoughts everyone, I will put a note on my calendar to update this thread in a couple of weeks as so many have been interested. Feel free to comment further, but apologies if I don't reply as I need a break now from thinking about it ;-)

 

[sammathias]

Open 'all' the radiators...vent all the air out of radiators, when system is cold put pressure upto 2bar then isolate boiler....no drop over a day or 2 then boiler is fine, when isolation is turn back on and there's a drop then it's your rads or pipework.

 

[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.