The customer said he has gone off unvented hot water systems

[n2o]

I've just been to look at an old hot water system and suggested replacing it with an unvented system. The customer said he has gone off unvented systems because of the trouble they have had with 10 UV systems connected with their holiday flat. Apparently, one of the expansion vessels corroded and failed causing considerable consequential damage. He (on behalf of the residents committee) has been in touch with the manufacturers about this and their concerns for the other 9 vessels. Several letters have been exchanged, but he hasn't got anywhere so to avoid further trouble the committee replaced all 10 expansion vessels at their own cost.

All 10 systems were installed when the property was converted to flats 10 years ago. I don't know what sort of guarantee you should expect to get against corrosion for an expansion vessel, but I would expect the vessel to last as long as the accompanying cylinder.

Apparently, these vessels are of steel construction with a corrosion resistant coating. The manufacturers letters make no mention of this, they are only concerned as to whether the initial charge pressure was set to equal the incoming mains water pressure. Incorrect initial charge pressure causing the vessel to fail. I say that this is a total red herring and has nothing what so ever to do with the vessel failing.

Do you agree or disagree?

10 years old or not the fact that the manufacturer refuses to discuss the real reason for the failure leads me to conclude that these vessels were not fit for purpose and yet again the manufacturers would rather blame the original installer than admit that they are the ones at fault.

 

[LUNAT]

HI

typical of the manufacturers.always blame customers or installers.

 

[GforceJames]

10yrs for an expansion vessel, that seems like it did well. Considering the amount of work they do, I don't think it is that bad at all.

Why would 10 residents change them just for the sake of it, that is like saying ten people have the same car. Then after 10 years the alternator goes on 1 of them so all 10 change theres.

How long do you expect a appliance to last before things start to wear out.

James

 

[n2o]

Hello James,

It seems you are missing the point.

I would not expect an expansion vessel that has been designed for use with potable water to be manufactured from a material that will corrode and cause consequential damage to the property it has been installed in and I would not expect the manufacturer to claim that an incorrect initial charge was the cause of that failure. Diaphragm failure is not the issue here.

Nine residents changed them to avoid further consequential damage occurring to their property. I suspect you would have done the same if your property was at risk.

Wearing out is one thing, but this is something else!

 

[GforceJames]

What was the main cause of the corrosion, were they installed in a hard or soft water area. Is adequate water treatment present, the internal diaghraphm would have had to have failed for water to come in to contact with the metal of the expansion vessel.

Most potable water vessels use a condom style of diaghraham, with water only entering the inside of the rubber. Rather than one piece of rubber stretched between the two halves.

James

 

[n2o]

James,

Thank you for your interest in this matter.

You ask, what was the main cause of the corrosion and were they installed in a hard or soft water area, etc. I don’t know the answers because I haven’t seen the vessels and the properties concerned are way beyond my travelling radius. I would have thought that these are the type of questions that would be more relevant than whether or not the pre-charge pressure was equal to the incoming mains pressure.

Most expansion vessels of this type have a pre-charge pressure of about 3.5 bar. If that pressure is not suitable for the installation conditions the worst that can happen is loss of water to waste and definitely not for the vessel to fail or am I missing something?

 

[superdupergasman]

I think it is a small minority that fail, of the thousands I have seen and replaced or recharged I could count maybe 2 or 3 that have started to leak.

It would be unfair to say that anything is 100% reliable and there will always be floods, how main rads pinholing have brought ceilings down...I bet a fair few in comparasons to a fails exp vessle.

 

[Gasguru]

Was the pre-charge pressure checked annually as it should be under the service. If the pressure is not maintained the bladder is stretched more and more sometimes causing it to perforate as it wears against the vessel wall/seams. Once that happens ccorrosion of the vessel is inevitable.

Vessels are only £30 or £40 so a minor expense after 10 years. Most customers spend nothing on routine maintainence and then complain when it all goes wrong. Anyone ever bothered to check the pressure reducing valves are still correctly set?...most I see don't even have a guage plumbed in for simple checking.

 

[Paul Barker]

I have to agree any unvented aftermarket job i have ever been to has failed through 10 years of nil servicing.

They are such hasstle I won't go to them anymore.

For the handful I fitted I know the customers well and get access for maintenance and checking. Usually they have another plumbing issue at least once a year.

All of the unvented's fitted in bulk to newbuilds or conversions that I have seen were not commissioned and had installation faults.

One was ready to blow call in middle of night from insurance company i was only person with ticket anywhere near Pontefract had to go as an emergency 1 am van blew up on way but got me there on 3 cylinders system was a total bodge by a builder who had built a whole estate like it. i wrote to everybody and never got a bye your leave or a reply.

Van was terminal.

Insurance company never paid.

Don't try telling me it was installed correctly and maintained pull the other one.