Gate valve mystery

[DLaing]

I may be about to show my ignorance but....

My hot water cylinder has (amongst others) two pipes of interest: one exiting mid-way up and connecting to a 3-way electronic valve that's wired to my boiler timer and the other exiting at the bottom and linking up to the middle down pipe of the 3-way valve (stay with me!) via a gate valve (the one with the round red handle). This valve is now leaking.

I'd imagined that it would be fairly simple to replace the valve: turn off the water, drain the tank, fit new valve etc. My only concern is that the pipework gets hot when the central heating is turned on. I have a sealed pressurised system that I had (perhaps naively!) assumed was completely independent of the hot water system.

Am I missing something here or are the two systems in some way linked and the job is not as easy as I imagine, or is it some strange coincidence and the job a straightforward one?

 

[kevplumb]

any chance of a pic ?
where is the valve leaking from ?

 

[DLaing]

I think I'm getting a better understanding here! Have a look at this link:

http://www.diydoctor.org.uk/projects/domestic_hot_water_systems.htm

My system looks like the picture on the right (indirect cylinder): Pipe #3 is connected to the leaking gate valve and pipe #4 to the 3-way electronic valve.

The implication from this article is that the hot water is heated as a by-product of the central heating system. My hot water can be heated independently from the heating, so is it possible that the electronic 3-way valve (connected to the boiler timer) is used to select either a direct boiler feed or a feed from the heating system?

So where does that leave me? I'm not sure what I have to drain to remove the valve!

By the way, the valve is leaking from the point the spindle enters the body.

 

[kevplumb]

try tighteniny the nut where its leaking may only be the gland

 

[DLaing]

I tried tightening but that briefly made things worse! I may have another go and see if I can stop the leak.

If that doesn't work, any ideas on what to drain?

I'm moving in January, so plan B may be to put a drip tray under it for now until it becomes someone elses problem!

 

[kevplumb]

would think its a balancing walve for the hot water side
if you turn the system off
close the valve (count the turns )
remove the red wheelhead
remove the gland nut (top of the valve )where the spindle enters
wrap a couple of turns of thread tape round replace the nut/head etc
open the valve to where it was then tighten the nut a little more

if you need to renew it its a drain down

 

[fitz1]

its the by-pass valve. i:e. a gate valve

 

[kevplumb]

if its a by pass why is it connected to the cylinder