As above, with an unvented hot water system, I thought the hot water pressure should be the same mains pressure as the cold. It’s not - I’d say it was about 75% of the pressure. Can it be adjusted anywhere?
Can I adjust my hot water pressure - unvented system?
- Thread starter Mottie
- Start date
Sponsored Links
Do you actually mean pressure or do you mean flow rate ? they are not the same thing
If the cold is running higher than the hot unvented then the cold supply probably hasn't been piped from the combi valve, it'll be fed directly from the incoming mains (Before the reducing valve)
Sponsored Links
Yes, sorry. I think I meant flow rate. Can anything be adjusted or shall I just leave it alone - it’s not a major problem, I think I’ve just noticed it because I’ve changed my bath and basin taps.
There should be a balanced cold water supply at the unvented cylinder,
Just another question: When filling a glass of water from the cold tap in my basin, it’s gin clear. When filling a glass from the hot tap, it looks chalky but on closer inspection it’s tiny air bubbles that clear in about a minute. Any idea what’s causing this?
- Joined
- 22 Jan 2007
- Messages
- 8,310
- Reaction score
- 4,131
- Country
Air is released from the water easyer when its hot, see it on combis all the time between it being hot and having went through a turbulent flow. its nothing to worry about, its in the cold too just dissolved so you cant see it
May be a silly question but would it do any harm to have a pressure gauge like I have on the heating system permanently fitted to the hot water system to monitor the pressure? If so, where would that need to be fitted - to the inlet or outlet of the hot water cylinder (or would it make no difference) and would it be like a tyre gauge - do you check the pressure with nothing running?
pressure doesnt really mean anything, it is just simply what the pressure is when nothing is being used , when you run an outlet that is flow rate which is what you are concerned about
Ah right, thanks. So the valve I have, in addition to the red safety valve that goes to my tundish, has a grey cap with arrows pointing in either direction with + one side and a - on the other with a small black blanking plug in the middle. If I remove the plug there's an allen screw in there. If I turned the screw in the direction of the + will that increase the flow rate through the hot water cylinder (without affecting the pressure) and therefore give me more hot flow at my taps?
My valve looks like this: https://www.screwfix.com/p/strom-cold-water-inlet-control-group-22-x-22mm/1610v
Looking at the write up on it, it says that it 'reduces the water pressure to a safe and acceptable 3 bar for domestic water cylinders'. So, presumably that is factory set, non adjustable, and the adjustable screw only controls the flow?
My valve looks like this: https://www.screwfix.com/p/strom-cold-water-inlet-control-group-22-x-22mm/1610v
Looking at the write up on it, it says that it 'reduces the water pressure to a safe and acceptable 3 bar for domestic water cylinders'. So, presumably that is factory set, non adjustable, and the adjustable screw only controls the flow?
Last edited:
the red pressure relief valve is pre set and cant be adjusted, the grey regulator should be factory set but can be adjusted but to be honest it shouldnt need to be unless it is faulty, not something a Diyer should be doing though as you can upset the whole control group if you get it wrong
Unfortunately, my advice is that unless you are G3 (unvented) qualified you should not be working on an unvented HW system from the combination valve till after the EV on the hot side.
You could potentially cause a dangerous situation, without knowing it, especially if increasing the inlet pressure above the manufacturers specifications.
Do you know what your cold mains dynamic pressure and flow is?
You could potentially cause a dangerous situation, without knowing it, especially if increasing the inlet pressure above the manufacturers specifications.
Do you know what your cold mains dynamic pressure and flow is?
I think that’s true. In the picture above, mains feed goes in the top, feed to the hot water cylinder comes out the bottom, the port with the blanking plug goes to the white expansion cylinder, the 15mm connection goes to the tundish and the remaining 22mm compression connection is blanked off. Should the cold feed come out of that one?
Sorry, no idea on that.
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
