G3 unvented cylinder limited to 2 bar mains pressure?

Joined
5 Oct 2015
Messages
46
Reaction score
1
Country
United Kingdom
Hi All,
Just wondered what your take was on the following. I moved into my property 2.5 years ago. The boiler fitted is an Ideal iStor - I know they have a bad reputation but mine is serviced yearly and it hasn't caused me any problems to talk about really.

Anyway, the house did have an old lead supply which has since been changed to a new plastic pipe mains. Since then (over 6 months now) I've not noticed a difference at all in flow rate - if anything its worse than it was.

I've determined that next to my mains inlet is a PRV set to 2 bar yet I believe the house is receiving far in excess of 2 bar as it was measured on installation - I just cant remember what it was. On reading, the boiler manufacturer indicates that the 2 bar setting is indeed correct. The boiler advertises a flow rate of up to 35LPM and around 11 on an empty cylinder. I get 8/9 LPM - and that's on the taps next to it! All other outlets are the same as the house is limited from this PRV. Every pipe seems to be 22mm copper.

Now what I don't get is that I can manually increase the pressure on the PRV and the water flows much better to a point where the shower is great. However, the tudish begins to drip water assuming the pressure relief valve is giving way. So, if I set the PRV off the mains the at 2 bar (which is exactly how it is indicated in the ideal installation manual) I get poor flow rates. Why would a supposed mains fed boiler be limited to 2 bar? Should I actually be getting better flow or is this actually quite good?

I've ordered a new PRV and am just waiting for it to be delivered before i can try and fit it- I assumed something was wrong with that. Incidentally, the boiler company are not interested (as its not actually the boiler unit) and the last time they serviced it said there were no faults - the bloke actually didnt know what the PRV was until I told him!

Any advice would be appreciated. Thanks
 
Sponsored Links
Like DIY Gas advice, we really should not encourange someone to be playing about with G3 Cylinders especially the pressure controlls and PRV/PTRV as its not a DIY topic it requires certain qualifications outside normal scope of plumbing.
 
Dont worry I wont be playing around with the PRV - it was a one off to see the outcome of increased pressure on dial knowing the boiler had a Pressure relief valve fitted. I've let it sat at 2 bar ever since but its a nagging issue. Incidentally the pressure on the dial does change when I turn a tap on - it reduces. I assumed it would be static which is why I purchased a new PRV. Is it possible for a flow rate of up to 35lpm with 2bar restricted mains?
 
You prob have a cheap pressure reducing valve fitted. The cheap ones tend to drastically reduce flow if set below 3 bars.

Simple solution to your problem is to get someone qualified to work on unvented out to change the pressure reducing valve for a high flow one

I find the Reliance valves and the Honeywell valves are good. You pay a bit more for them, but they won't significantly reduce the flow rate when set to 2 bars
 
Last edited:
Sponsored Links
That's great. It does look like a cheapo one. The original Ideal valve is branded caleffi in the installation guide. This thing has no branding at all so I think you're spot on. I've order a JET PRV - not that I know anything about this kind of stuff it has a a simple way of setting the pressure so I assumed it would be decent. Hope I've not introduced another budget replacement!
 
If you were G3 registered, to replace the manufacturer supplied valve with a different one is frowned upon. As a DIYer, you are free to do what you see fit.

It is clear that you are exceeding the manufacturer metrics because the safety valve lets by at the higher inlet pressure setting.

Normally, a PRV is set to prevent the cylinder/store from being stressed outside its comfort zone; if you up the static pressure there is a real danger you will rupture the tank when the water expands by 5% or thereabouts by heating it - then you'll need a new boiler.
 
I've not fitted it yet but I did read a few posts on this website and the JET Name was mentioned a couple of times in relation to PRV's. Its not fitted yet anyway, but are there any technical reasons why the JET PRV is 'shyte'?
 
Had a neighbour install the PRV this evening set at 2 bar as recommended by Ideal. Flow has increased by a litre a minute or so but its still far below the 35lpm indicated in the boiler blurb and the 11lpm supposedly on a depleted tank - I dont get 11lpm on a full tank in the hot tap next to the boiler!
I couldnt help but look at the mains where it enters the house. Can anyone explain why the mains enters the house with a big pipe which seems to be instantly reduced to 15mm. This then attaches to the PRV which then leaves on a 22mm pipe. Could this be restricting flow? Can anyone shine any light on this?
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top