gravity hot water

[tplus2]

have been ask to install a zone valve linked to a cylinder stat on the primaries from a gravity hot water boiler incorparating a bypass valve just before the zone valve.
everything tells me this is not the way to do this and something tells me it may not comply with regs.
I have always been taught that gravity pipes you do not restrict and the only solution is to convert to fully pumped.
Please can some one confirm if i am right or wrong please.

 

[seco services]

read up on c plan system

your not restricting vent pipe etc as the zone valve is fitted on the return

 

[tplus2]

thank you for that advice

 

[JohnD]

I did something similar recently on my mum's old system. The 28mm 2-port valve is quite expensive, but I happened to have one, and a additional pump which I fitted, but on consideration it would probably have been better to fit a 28mm 3-port and make it fully pumped that way.

I am not very good at plumbing and was scared of having to alter a lot of pipes in a cramped space, but my BiL kindly helped me.

BTW, although I had previously fitted a Magnaclean and given it a thorough chemical clean, when I changed the HW to pumped, a lot of old sediment was dislodged from the previous gravity circuit, where I imagine there had not previously been enough flow to shift it.

Changing to fully pumped also makes the cylinder heat up much faster, and reduces boiler cycling. On Gravity with no cylinder temp control, the boiler just kept itself hot all day. Looking at the gas meter usage, it appears to be running cheaper since the change. I insulated the DHW pipes as well, they have a long and wasteful run.

I am a householder not a pro

 

[tplus2]

thanks for feed back johnD,will proberly convert to fully pumped