combi boiler: plumber mistake?

pardo

I have a 10 year old combi boiler that started loosing pressure when central heating was switched off. When pressure was refilled to 1.1 bar, it then went up to no more than 1.8 bar with heating on. Then pressure was lost again overnight when heating was off.

Plumber said expansion vessel needed replacing with an external one. Said he ws sure that this would solve the problem. Did this job for £180 (£40 parts plus 30 mins work!). Boiler pressure went down again overnight when switched off.

Plumber comes back says that pressure relieve valve needs replacing. I said perhaps expansion vessel did not need replacing at all. Plumber says it definitely did, and that when the expansion vessel goes, the PRV can be damaged as well. He swears he is 100% sure expansion vessel was faulty and needed replacing.

I suspect that the only real problem was a faulty PRV and that I threw £180 down the drain. I also have an ugly cylinder that takes a lot of useful storage space. The fact that pressure did not go above 2 bar with heating on is one of the reasons I feel this way. Also, googling around I did not find that a faulty PRV is necessarily due to a faulty expansion vessel.

Have I been swindled?

Mee

Have you check he is registered? 

pardo

Yes, he is registered.

Hasbeen

Pressure relief valve is always first to look at. You could have checked this your self by observing any discharge by pipe on exterior wall. Is problem now fixed? After fitting valve.

Undervalued

pardo said:

Plumber said expansion vessel needed replacing with an external one. Said he ws sure that this would solve the problem. Did this job for £180 (£40 parts plus 30 mins work!). Boiler pressure went down again overnight when switched off.

Plumber comes back says that pressure relieve valve needs replacing. I said perhaps expansion vessel did not need replacing at all. Plumber says it definitely did, and that when the expansion vessel goes, the PRV can be damaged as well. He swears he is 100% sure expansion vessel was faulty and needed replacing.

I suspect that the only real problem was a faulty PRV and that I threw £180 down the drain. I also have an ugly cylinder that takes a lot of useful storage space. The fact that pressure did not go above 2 bar with heating on is one of the reasons I feel this way. Also, googling around I did not find that a faulty PRV is necessarily due to a faulty expansion vessel.

Have I been swindled?

Possibly / possibly not (although the price seems quite high even assuming the work was needed).

My layman's opinion based on what I have learnt from various heating people over the years.......

As I understand it, anything that causes the PRV valve to operate can leave it slightly leaking as dirty water / rust / grit from the system can get trapped in its seal. Sometimes giving them a deliberate blast out and snapping them closed will make them seal again but they can become like a slightly dripping tap. So if the pressure was fluctuating and going too high the old PRV may have suffered.

I am told that some makes of boilers are so badly designed you can't replace the internal expansion vessel without taking the boiler off the wall! Hence the quick and ugly fix of fitting an external one!

pardo

Hasbeen said:

Pressure relief valve is always first to look at. You could have checked this your self by observing any discharge by pipe on exterior wall. Is problem now fixed? After fitting valve.

It seems that pressure is holding at the moment, although if it is slowing decreasing it may take longer to detect. I also think that the PRV should have been checked first - that the plumber did not do as he was sure it was the problem was the expanding vessel.

Undervalued said:

As I understand it, anything that causes the PRV valve to operate can leave it slightly leaking as dirty water / rust / grit from the system can get trapped in its seal. Sometimes giving them a deliberate blast out and snapping them closed will make them seal again but they can become like a slightly dripping tap. So if the pressure was fluctuating and going too high the old PRV may have suffered.

Thanks. My question boils down to: can a PRV fail (and cause loss of pressure when heating is off) even if the expansion vessel is OK? If so, I believe the plumber has made a mistake in replacing the expanding vessel without checking the valve first.

Undervalued

pardo said:

Thanks. My question boils down to: can a PRV fail (and cause loss of pressure when heating is off) even if the expansion vessel is OK? If so, I believe the plumber has made a mistake in replacing the expanding vessel without checking the valve first.

Well anything can fail! It is basically just a spring holding a rubber tap washer shut. It is not very likely to start leaking unless, as I mentioned, something or somebody activated it and either the washer started breaking up or a bit of grit got stuck in it. The plumber may well have used it to drop the pressure prior to replacing the expansion vessel. However, that doesn't necessarily make it his fault or mean that the vessel wasn't faulty first.

neilmcl

Generally PRV and expansion vessel failure go hand in hand so it doesn't surprise me you need both doing. In any case I'm not sure how you're going to prove that the expansion vessel was perfectly OK now that it's long gone.

nofoollikeold

1. A faulty expansion vessel can cause the PRV top operate.
2. As stated above, once operated, the PRV can often allow water past even below its operating pressure.
3. I don't think you have been "swindled", but it is possible the plumber got it wrong.  It happens.
4. £40 for parts and £140 for 30 minutes labour suggests he / she was charging £280 per hour.  Bit steep even for Central London.  I'd struggle to fit one in 30 minutes, I'd be looking at an hour, more if access difficult.
5. If it were me who had fitted the new expansion vessel, I think I'd compromise by fitting a new PRV for the cost of the part, i.e. no labour charge, provided its not a "boiler off the wall" job, like some Worcester Bosch's.
6. If it is an off the wall job, consider getting the internal expansion vessel checked / replaced at the same time.
7. Probably best to chalk it up to experience.  Otherwise you'll need someone else (qualified) to check the original expansion vessel, and give an opinion on whether it could reasonably have been though faulty or not.  That won't be cheap, and to say nothing of the hassle of pursuing the first plumber.

pardo

neilmcl said:

Generally PRV and expansion vessel failure go hand in hand so it doesn't surprise me you need both doing. In any case I'm not sure how you're going to prove that the expansion vessel was perfectly OK now that it's long gone.

The old expansion vessel is still there and I don't think it has been touched at all, so in principle it may be possible to check if it is faulty. Having said this, I don't intend to make a claim against the plumber, as the amount of money involved is not worth the time and hassle. The main reason I want to understand this is this plumber was reccommended by  a friend of mine and I want to be sure of my case before I give her any feedback. I don't think I will use him again, personally.

nofoollikeold said:
3. I don't think you have been "swindled", but it is possible the plumber got it wrong.  It happens.

I agree, we all make mistakes. In this case however the plumber did not accept any responsibility and just told me that the expansion vessel was "100% faulty".  I am not convinced that one can be sure of this, although I accept it is possible.

nofoollikeold said:
4. £40 for parts and £140 for 30 minutes labour suggests he / she was charging £280 per hour.  Bit steep even for Central London.  I'd struggle to fit one in 30 minutes, I'd be looking at an hour, more if access difficult.

It is not in London! The job took 30 mins (I was there). All he did was to add a T junction on the loop and connect it to the external cylinder, that he had previously anchored to the wall. He did not drain the system and did not put any additives. He claimed that there were no additives in first place because the water in the system was rusty (based on its colour), and therefore there was no point in adding any chemicals at this point.

nofoollikeold said:
5. If it were me who had fitted the new expansion vessel, I think I'd compromise by fitting a new PRV for the cost of the part, i.e. no labour charge, provided its not a "boiler off the wall" job, like some Worcester Bosch's.

He did fit the new PRV free of charge. This took him 15 mins. The part looked quite inexpensive, but he did not charge me anyway.

nofoollikeold said:

7. Probably best to chalk it up to experience. 

Indeed! As I said, I just want to make sure I have a case before I give my friend a feedback on him. She has found him many jobs in the past and may find more in the future. I take professional reputation seriously and don't want to say anything unfair.

bris

It sounds like the expansion vessel was a fault though so not sure why you think it wasn't. Pressure rising and water being ejected through the PRV is an expansion vessel fault. The PRV cant cause the pressure to rise, even it it was leaking the pressure would just go down not up.

The simple test for an expansion vessel is to test the valve, if water comes out then its kaput, if a little air then it's a recharge.
It's also true about replacing internal vessels, some are just not worth replacing and external ones are much quicker and cheaper (well yours wasn't cheaper thats for sure). I do external ones for about £120 (including parts which are about £40). 
I only recommend them when there is a cupboard  they can be hidden away in though.