noisy 3 way valve - position of CH header tank

[tim48]

Domestic pumped hot water and central heating system.
whining noise from 3 way valve in airing cupboard, if I bleed air from bleed valve adjacent to it - noise stops, however noise starts again 30min to hour later and I bleed the valve again - any ideas where all this air is coming from?

Reading through the other posts - has lead me to ask another question?

Should the central heating header tank be higher than the the cold water storage Tank and if so, by what part of it and by how much?

I replaced the Cold water tank a year ago - and placed the new plastic one on top of the old galvanised steel one. Which resulted in the bottom of the central heating header tank being 25mm lower than the new Cold water tank. Therefore the top of the water in the header tank is 250mm lower than the top of the water in the cold water tank. Could this be causing the problem of the water in the header tank being HOT! and over flowing regularly.

 

[seco services]

better to have the f/e lower than the cws.

if you get a faulty coil in your cylinder the cws water will pass to your f/e tank.
better than central heating water in your bath water.

you maybe drawing in air down your f/e vent pipe.
get a jug of water and place the vent pipe init see if it draws all the water in.

 

[twgas]

Your problem is nothing to do with the relative position of your tanks. The problem is either ; the cold feed and open vent wrongly configured and/or a restriction in the pipework around where the cold feed and open vent join the system. This needs to be sorted as soon as possible becuse you will have sludge building up all round the system causing the efficiency to drop.

 

[tim48]

Thanks for the speedy response
I have just tried the jug test with my son holding the jug under the vent pipe with 500cc of clean water in it, while I bled the bleed valve in the airing cupboard again. Water level went down to 400cc then up to 550cc back to down to 150cc before discharging discoloured water up and over the top of the 750cc jug.
The indirect hot water cylinder is dated 1995, we live in a very hard water area,and I have had on average 5 adults living in the house, having showers.

 

[tim48]

Thank you for your help
The cold feed from the header tank drops to the attic floor with an isolation valve and then a tee off to form the vent pipe which rises back up and over the top of header tank. The feed then continues through the airing cupboard to somewhere? without visable connections.
I have seen in CH diagrams that the tee off for the vent pipe should be in the airing cupboard or nearer the valves?