Replaced hot water expansion tank, now droning noise from system.

[Red One]

My old hot water expansion tank was knackered (water coming out from valve on top)
I got a similar new tank fitted. (also checked the pressure pre fitting)

Ever since, on turning on any hot tap, there is a loud whining droning noise for about 5 seconds, then all is ok again.

How can I fix this, is it an airlock or something? Note: the system was not making any noise before the new expansion tank was fitted.

 

[Bonni]

Maybe Googling water hammer and trying some of those solutions may help.

 

[Madrab]

I take it you have an unvented cylinder?? Who replaced it & did they have the correct quals? They should have ensured everything was ok once replaced. If it's not right they need to return and sort it. It can be down to incorrect pressure in the EV or the pipe supplying the EV has air in it and that's being slightly over pressurised when the water heats up. Do you get a slight rush of hot water on opening the tap and it then settles?

 

[ianmcd]

you shouldn't have fitted the replacement expansion vessel yourself, post a pic of the new expansion vessel please

 

[Red One]

Its buried behind racks of clothes in the airing cupboard so difficult to photo. It was an exact replacement for what was there. A Grey coloured potable tank, I think it was 12 or 18 litres, but in any event, it was the same size and type as the original.
I checked the pressure on the top valve when I took it out of the box, and was pressured to what it said on the box, (which I can't remember now. It was fitted a few weeks ago.). On reading elsewhere, the one thing I didn't do was check the water pressure for my property and match the pressure in the expansion tank to that. Could that cause the noises, given there was no noise coming from the old vessel?

 

[Madrab]

That is not how it is set up, it is not calibrated to the mains pressure of your property. The manufacturer only sets the EV pre-charge generically and as each system can be different, it needs to be setup specifically to the individual installation. You need a qualified unvented HW engineer in.

Unvented cylinders and their safety devices are not DIY'able and have the potential to become very dangerous if they are not installed or maintained properly.

 

[Red One]

Yes I am aware of all that. I am also aware that many people do fit their own expansion tanks without issue.
I posted elsewhere of the issues a previous engineer caused with my hot water system, charging me a fortune and leaving the system in a worse state than it was when he first came in. I have asked for advice to see what would be causing this noise, as I believe it will be an easy enough fix ultimately. There are numerous articles and sites online that say the pressure in the exp vessel needs to be equal to the mains pressure in the house, and as far as I can see, that's the only thing so far I have not done, given it was a direct one for one replacement of an identical tank both in type and capacity.
Are you saying this is not the case? You stated the exp tank pressure is not calibrated to the mains pressure of the property and then in the next sentence you said because the pressure in the EV is set by the manufacturer generically it needs set up to the individual installation??

 

[Madrab]

I am sorry to hear of your previous experiences with an obviously dodgy engineer, I am the first to agree that our industry is plagued with unexperienced, unqualified chancers that if they're lucky haven't injured/killed anyone yet. That still doesn't detract from the fact that it can be potentially dangerous for a non qualified person to work on something that, if the safety devices fail due to lack of or incorrect servicing, can literally become a ticking time bomb.

Ultimately of course the decision is yours as to how you wish to proceed.

Returning to the OP ... that's not what I said ... what I said was the EV's pre-charge is not calibrated using the mains water pressure as a guide, my apologies if that wasn't clear. Any other information anywhere that states that is fundamentally incorrect. If that was the case then one of last weeks services would have had a pre-charge of over 5 bar

I also appreciate that it does all seem relatively easy to do but again, something that has the potential to extremely dangerous should, IMO, not be played with which is why it specifies that a qualified engineer needs to work and service these types of unvented systems.

 

[Red One]

I appreciate where you are coming from, but I do really get exasperated at the number of posts asking for advice on a DIY forum which get the immediate answer, "call an engineer". I have fitted a new central heating water pump, replaced burner jets, and added a magnetic filter to my heating system. I have bled the complete system and I have tore apart the burner and rebuilt it and I have serviced the oil pump. I have also carried out numerous other plumbing jobs myself without having to call in an engineer, because most jobs are not difficult if you are logical and decent at doing home repair work.
I am fully aware of the risks with pressurised systems, but I like to think I have a reasonable level of common sense, and I know my own limitations. I know where to draw the line. The risk of failure or explosion from an unvented cylinder is extremely remote and would take a catastrophic failure of several safety systems before such an event would happen. In any event, I cannot see how unbolting an EV and bolting on an exact same EV would increase the risk at all. Even manufacturers such as Kingspan have instructional videos on Youtube explaining how to change an EV, its hardly difficult.
On checking, droning and whining from the hot water system is a fairly regular occurrence, and all I am trying to do at the moment is get an idea for what I may have missed. I am sure this is an easy fix. There was no drone from the old EV installation, so I am fairly sure there is no valve failure. But if it comes to that ultimately, I would get an engineer in to check and replace a safety valve. I will however do what I can myself first with the help of advice from here, and what I can source elsewhere, which I have always done when faced with issues around the house.

 

[dilalio]

I do really get exasperated at the number of posts asking for advice on a DIY forum which get the immediate answer, "call an engineer".

Call an engineer

 

[Liamw23]

I take it you have an unvented cylinder?? Who replaced it & did they have the correct quals? They should have ensured everything was ok once replaced. If it's not right they need to return and sort it. It can be down to incorrect pressure in the EV or the pipe supplying the EV has air in it and that's being slightly over pressurised when the water heats up. Do you get a slight rush of hot water on opening the tap and it then settles?

That's the exact problem I'm getting at the minute!

 

[Liamw23]

Did you ever fine out the reason for the problem?

 

[HERTS P&D]

Did you ever fine out the reason for the problem?

No, he never found out, he called out an engineer who fixed it without tell him what he had done.

Andy

 

[Dangee]

Not many people bother doing there unvented qualification, even though I see potentially explosive installations regularly..... But they get away with it, no benchmark or notification, no comeback. New builds are the worst.