Mattg4321

It's one of these https://www.mrcentralheating.co.uk/water-storage/unvented-cylinders/thermowave-18-litre-unvented-potable-expansion-vessel?gad_source=1&gclid=CjwKCAiAzba9BhBhEiwA7glbaqbL_VFwijXyCmtOYqZedccRbzUq-NnH4RZxg7MUGEn2gvyofQtMVBoC2ywQAvD_BwE

It tails off, so 28LPM wouldn't be sustained for too long. Will see how things go for a few weeks I think.

60 degrees

The EV provided by Joule isn't actually a (the) Joule product. It's a Global Water Solutions EV. As an update. I pumped the EV back up to 2.5 bar to see what would happen. Noise got much worse. Even just opening basin tap caused fairly loud noises from the EV/cylinder. I let it back down to 1.5 bar and if anything seems slightly better than before. Only opening the bath tap wide open suddenly causes the gurgling/vibrating noises. If opened gently it's just a moderate hiss as the EV empties presumably. Also notably I tried measuring flow at hot bath tap. Got 28 litres per minute. So significantly more than the outside tap directly off the main. I guess this is proof the EV is acting as an accumulator. I can only think it must be the large difference between static pressure and dynamic pressure causing the noise. Maybe the diaphragm bottoming out? For now it's only a minor problem in it's current state to be honest. I think the only way to fix is to get a better flow by upgrading the main.

Sorry for the poor picture. Yes, it’s after the PRV. Between that and the cylinder

Yes

Yes although EV from pipework to cylinder. Which looks fine from my research.

Not sure that I’ve ever seen or heard of an AAV on the DHW side! Fit where exactly and how would it help?

I've tested the pressure on the balanced cold/hot at 3 bar, so that rules out PRV leaking by? Both PRV and EV only been fitted a week or so - hope they are not faulty already! Gut feeling tells me its something to do with the way its plumbed or the supply rather than faulty components

Noise was much worse at 2.5 bar than at current 1.5 bar. The flow isn’t the main problem, I just want to stop the noise or mitigate it as best I can!

Well it’s not a million miles from what I’m getting when I measure it I suppose?

Looking at it properly I just measured the black alkathene main at 22mm external diameter. According to Google this could be either 15.5mm internal or 14.1 depending if Class C or D. Nominal size is 1/2 inch. This is approx 15m in length from street. Then I have approx 12m of 15mm copper pipe to position of outside tap and kitchen tap where I carried out the test. Internal diameter 13.6mm. Do you still think I have a restriction? The length in total is much further than your calcs - sorry if I provided duff info! EDIT. Also goes through a 15mm stop cock and numerous fittings - mostly copper but including 1 or 2 push fit plastic I seem to remember. Cylinder is 250 litres and the EV is 18 litres.

Stop cock in street looks new. Last 5-10 years. Blue pipe I seem to remember and definitely has a quarter turn handle on it. Operated by hand easily.

Just checking the EV instructions. I think it says 65% of max pressure. So 65% of 3 bar. Equals 1.95 bar However there is a pre charge acceptance factor table. But I don’t really know what it relates to at a glance through instructions.

I just repeated the test. Pressure measured at the kitchen sink directly off the main. New pipework so won’t be furred up etc Had the outside tap fully open. Also directly off the main. static pressure. 3.6 bar dynamic pressure. 1.4 bar with outside tap wide open flow rate at outside tap with it wide open. 18 litres per minute outside tap fed by 15mm copper not sure what that tells me!

Thanks. So it seems like I need to get a new main in. 25mm or perhaps even 32mm if there’s any benefit to that? Then fit a 3 bar PRV at stop cock to match the 3 bar PRV at cylinder. Should sort my dynamic pressure problem and potential backfeed problem at new kitchen tap? I tested dynamic pressure on the main. Ie before the cylinder and PRV. So it can only be a problem on the main or the stop cock (which is almost new and fully open) I think? Guessing that black pipe is just too small. The stop cock is 15mm copper as that’s apparently the size of the black main internally. Then steps up immediately to 22mm copper to cylinder.

Looking like this will be the new tap in the not too distant future. Assume it means I don’t need to worry as it says it’s protected against backflow with an integrated non return valve?

It’s in 22mm copper and around 800mm

At the moment it’s one where the hot and cold are separated right to the spout. But soon to be changed!!

I do have what I assume to be thermostatic shower. Also a couple of oldish mixer taps. Assume 15 years ish. Balanced cold feeds everything bar an outside tap and the kitchen tap which is teed off near stop cock

22mm non return valve on hot outlet (at top of cylinder) - not that I can see... No pressure reducing valve at stopcock. Mains pressure at kitchen sink is 4 bar. Everywhere else after combination valve adj to cylinder measured at 3 bar. Not sure what effect those 2 things would have. I've not noticed them on other jobs I've been on either though - not that I make a point of looking. Sure you'll enlighten me! (please) When bath tap is fully on, flow elsewhere upstairs slows to not much more than a strong trickle!

Yes retro fit into late 60's build with black alkathene main. As per first post I was told that I needed a bigger main, so this isn't a gripe with the plumbers really. More of a question as to whether I can do anything to mitigate the noise in the meantime before I get the main upgraded later this year. Sounds like it may not be wise to drop the EV pre charge below 1 bar, so perhaps it has to be lived with as is now. Plumbers saying 25mm blue MDPE needs to go in. I'm in a fairly large village/small town and water pressure is good (4 bar). Distance from road to stop cock around 15m. Perhaps 25mm is fine, but any benefit to 32mm? I guess it will have to be stepped down both ends to 25mm at meter and 22mm copper in house, so perhaps not really.

Thanks for the explanation. The gurgling/vibration noise has got better since the pre charge pressure was dropped to 1.5 bar. It doesn't seem to happen if a basin tap is turned on now. Mostly only the bath. With every other tap its a moderately loud hiss for a while until presumably the EV has emptied. It seems it's probably something I have to live with until we get the water main upgraded to 25mm blue MDPE? The dynamic flow pressure of 0.8 bar seems to be the root cause here and everything else is a compromise because of this?

Hi all Recently had a Joule 250l indirect unvented system fitted. Was told beforehand that incoming main probably needs upgrading. Currently 3/4 inch black MDPE. Around 15mm internal I believe. Plan to do so as soon as funds allow. When hot water is drawn off after it’s been heated/left for a while then we get a fairly loud gurgling noise from the expansion vessel/cylinder area. The plumbers been back and I think released some air from the expansion vessel, which seemed to have made it a slightly less aggressive, but not cured. Im struggling to get them back and just want to get this sorted it it’s something I can do. I’ve checked pressure on the main and on the balanced cold. 4 bar on the main and 3 bar on balanced cold. This drops to slightly around 0.8 bar with the bath tap fully open. A consequence of the main being undersized I think?? Ive checked the pre charge in expansion vessel (after shutting off cold supply and opening a tap to release pressure) and it’s about 1.5 bar. I think it was 3 bar from factory judging by the sticker. From what I’m reading the pre charge should be 0.2 bar below the dynamic flow pressure of 0.8 bar? Setting it to 0.6 bar seems low though and I don’t want to mess about with something I don’t fully understand without seeking some advice! Thanks in advance

I wouldn't be using a granny charger unless in an emergency. No PEN fault protection and doesn't comply with Section 722 of BS7671. Step the cable down to 6mm2 and do away with the socket or supply from a local circuit. If not familiar with Section 722 seek assistance.