Unvented cylinder reduced flow

[Burt Stormberger]

Hi guys,

I have an unvented cylinder that I had fitted to my 1980's build house a couple of years ago. The incoming mains to the cylinder was also upgraded to 22mm at the same time.

All has been fine but the last couple of days when filling the bath, the flow rate and/or pressure (I know these are often confused!) gradually decreases to the point that if I then turn on another tap the flow almost stops.

What I have also noticed is that when the taps are turned off, I can hear the cylinder filling up in the airing cupboard for a minute or so afterwards implying to me that the cylinder has been emptying quicker than it has been filling, which seems strange as I was under the impression that the incoming mains water was what caused the hot water to come out.

Anyone got any ideas what is going on? Is something the matter with my system or is it likely to be something up with the local mains?

Thanks in advance!
Burt

 

[muggles]

When was your cylinder last serviced? Might need some attention from a G3-registered engineer. Could be a faulty PRV, or muck in the control set

 

[Burt Stormberger]

The cylinder was fitted 2 years ago and has not been serviced. I wasn't aware that these are supposed to be serviced. The guy who fitted it did not mention servicing and I had one in the last house that went 7 years without a service! I have the boiler serviced each year. I'll look in to getting someone to take a look. Thanks for your reply.

Burt

 

[ScottishGasMan]

The cylinder has "room" for expansion, either via an airbubble or a white expansion vessel.

When you first open a tap, the sudden rush of water pressure comes from here, when you close the tap the noise your hearing is the water filling backing to the expansion tank or airbubble.

Most likley there is reduced flow rate coming into the cylinder, as above, it could be the control saftey group is clogged, or something else before hand like an isolating valve or stop cock is partly closed or blocked, or as you said low flow rate from the mains.

Hows the cold water running?

Unfortuenetly as has been said, it needs a G3 Unvented registered engineer to look at the cylinder/control group, the rest of the incoming water installation can be done by any plumber.

 

[simond]

As a G3 registered technician, I take the view that any owner of an unvented would be unlikely to put themselves in danger providing they replace components with new identical ones.

 

[ScottishGasMan]

As a G3 registered technician for an unvented cylinder manufacturer, i see too many fitted incorrectly to think that an owner could tell if its safe before hand nevermind afterwards. Obviously there are multiple saftey controls and the likley hood of a steam explosion are admitadly tiny these days, while there are regs in force it would be advisable to get somone trained to work with the equipment.

 

[simond]

I agree, there are plenty of moody installs out there, on the basis of what we see, regulations don't seem to get in the way of 30% of the trade.

That's one of the reasons why I think a DIYer couldn't really do a lot worse, especially if he bothers to read the instructions.

 

[muggles]

The cylinder was fitted 2 years ago and has not been serviced. I wasn't aware that these are supposed to be serviced. The guy who fitted it did not mention servicing and I had one in the last house that went 7 years without a service! I have the boiler serviced each year. I'll look in to getting someone to take a look. Thanks for your reply.

Burt

If you don't get it serviced annually, your warranty will be declared null & void by the manufacturer.

 

[Burt Stormberger]

Thanks for all the replies.

To answer scottishgasman's question, the cold also runs at reduced flow once the bath has run for a while.

Does that indicate which bit could be at fault?

Looks like I'll need to get a G3 engineer out but it's always useful to be in the know in advance ☺

Cheers
Burt

 

[ScottishGasMan]

Depends. The cold could be run to the bath as a balanced supply from the same saftey group for the cylinder. Try the kitchen tap, more often than not the will be fed directly from the mains but not garunteed

 

[Burt Stormberger]

Yes the mains pressure in the kitchen is fine at all times including when the flow is reduced from the cylinder when showering or running the bath.

I guess this confirms the idea that there's a flow restriction somewhere before the cylinder ie the safety controls?

 

[ScottishGasMan]

Yea, def sounds like it, good news as it's fixable, water board arnt always that keen on fixing external pressure issues so saves the hassle of dealing with that

 

[spareshunter]

As a G3 registered technician for an unvented cylinder manufacturer, i see too many fitted incorrectly to think that an owner could tell if its safe before hand nevermind afterwards. Obviously there are multiple saftey controls and the likley hood of a steam explosion are admitadly tiny these days, while there are regs in force it would be advisable to get somone trained to work with the equipment.

I agree whole heartedly with that comment.


I have been looking today and still have to find where it says it’s mandatory to be G3 registered to install or service an unvented system over whatever Litres. Anyone point me in the right direction would be appreciated.

 

[Burt Stormberger]

Thanks ScottishGasMan. If blocked safety controls are a possibility is it worth considering removing the controls and trying to clear them out by flushing water through the opposite way or is this impractical / unsafe as a DIYer?

 

[St0rmer66]

Thanks ScottishGasMan. If blocked safety controls are a possibility is it worth considering removing the controls and trying to clear them out by flushing water through the opposite way or is this impractical / unsafe as a DIYer?

You should be qualified to work on it at all. The most a user can do is pump up expansion vessel/reset air bubble on a Megaflo (both amount to the same thing) or drain it/fill it.