Question for plumbing experts - Unvented system

BoxerfanUK

Hi all,

We've lived in our current house for a couple of years and it's the first house we've lived in with a Megaflo unvented system.

When we moved in I was looking forward to high pressure showers without the need for a pump to boost it but I've been sadly disappointed as the pressure really hasn't been that good from either the showers or upstairs taps, quite pathetic TBH.

Anyway I'll get to the point. Today I was clearing out the airing cupboard and I noticed the pressure gauge on the red CH expansion vessel was only reading 0.4 BAR when as far as I know it should be around 1 BAR. I opened the filling loop and heard water/pressure going through but the maximum it would go to was 0.9 BAR. Correct me if I'm wrong but I thought it should go much higher than this and closing the loop when it reached 1 BAR.

I'm now wondering could it be that the 3 BAR pressure reducing valve is faulty and or the strainer is blocked? And if so could that be the reason for the poor pressure at my upstairs showers/taps.

As it is I'm going to get the PRV replaced as the cold water shut off built into it is seized and I can't shut off the water from here if I want to recharge the Megaflo.

NB: Static Pressure at mains inlet to kitchen cold tap is around 3.5- 4.0 BAR

Opinions very welcome.

Alex1983

Yes I would say it's very likely that the combination valve has failed. It will be easier to replace the complete block, I'd be very surprised if you can get the strainer out. You would need a G3 registered plumber to carry out the work.

BoxerfanUK

Hi Alex, thanks, yes I'm going to get the complete combination valve replaced anyway as the cold water shut off is seized open.

I wouldn't attempt to remove the strainer and yes I know it needs to be someone G3 registered.

Primarily I was just looking for advice as to whether this could be why my upstairs pressure is so poor.

Alex1983

Yes, I had it a few times, poor upstairs and liveable downstairs, last one about 2 months ago on a megaflo, the new combination valve is a lot smaller, they just need to tell the supplier the reducer pressure, usually 3.5bar and the pressure relief pressure usually around 5bar.

BoxerfanUK

Alex, the one I have is the same as the one below in the link although as you say the strainer part in my old one is longer. I was thinking of buying this and getting someone in to fit it.

https://www.amazon.co.uk/dp/B00GRQXB16/?coliid=I341LHY8U64AY9&colid=15OVZPJGRSS7T&psc=0&ref_=lv_ov_lig_dp_it

I've seen another type that has a pressure relief valve on it as well, although on mine the pressure relief valve is fitted separately a bit further along the pipe.

I didn't realize the reducer pressure could vary I thought they were all set at 3.0 BAR!!

Alex1983

I normally fit the one with the new pressure relief valve as well to be honest.

Just make sure which ever you buy the pressures match. It will say the pressures on top of the strainer and prv.

BoxerfanUK

Cheers Alex thanks for your advice, much appreciated.

SimonEnnis

Personally for things like this I would contact an expert.

Try city plumbing or easymerchant.co.uk and see if they can advise on exactly what you need.