Help needed to understand the purpose of another pipe and valve for expansion tank

[papaya]

Evening guys,

I'm slowly learning how my central heating system works and I would like to ask for your help to understand the purpose of the pipe and valve used with my expansion tank as I can't see the point there :disappointed:


I understand that the white pipe (bended) is overflow and the one with green insulation is the cold feed to the F+E and the other high paper clip type pipe is the expansion pipe for extra protection as all water through it will eventually drop back to the tank BUT I don't seem to understand the one on the right with the valve (circled).



The reason is that this valve controls the water from expansion tank to flow with the hot water from the left through the heater pump. If I turn it off, just the hot water from left will come through to the pump but if I turn it on, it will mix with the hot water comes from left and results in only cold water come through the pump. So what's the purpose of that and should I leave it on or off? I know it sounds stupid but I can't figure out why...


In addition, I would also like to know how could I check if the copper coil in my water cylinder has pinholes?

Many thanks! :blush5:

 

[Whyme]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

The valve is on the cold feed to ur heating, leave it open as expanding water uses it. Why do you think the coil has pin holes ??

 

[ecowarm]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

In addition, I would also like to know how could I check if the copper coil in my water cylinder has pinholes?

If your copper coil had pinholes the f&e tank would be constantly overflowing as the level in the 2 tanks try to equalise
​

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Whyme, many thanks for your quick reply.

For the pinholes, it is because my overflow is always dripping when the boiler is not on and I had discoloured hot water. I thought it was a coincidence as the discoloured water just happened after Wessex water did some work but when I called a plumber in to change our faulty motorised valve, he told me there are pinholes in the coil. The reason is that when he disconnected primary flow to replace the 3 port valve, there was water dripping from it and I could hear some hissing.

Any suggestions?

Thanks again!

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

ecowarm, thanks but mine stops when the boiler is working - either heating or hot water or both.

 

[diamondgas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It is a NO---NO .. to have a valve where you have!!!

Dodgy DIYer or plumber ALERT!!! :50:

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I agree. It's actually illegal under the water regs (of all things) to have any sort of isolating or service valve on the outlet of an F&E tank in a domestic dwelling.

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It is a NO---NO .. to have a valve where you have!!!

Dodgy DIYer or plumber ALERT!!! :50:

Thanks to clarify this but what's the purpose to have one then if this is not a good idea? I'm just trying to understand it.

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

This is the cold feed to the heating system. The pipe needs to be there but not the valve.

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I agree. It's actually illegal under the water regs (of all things) to have any sort of isolating or service valve on the outlet of an F&E tank in a domestic dwelling.

I know the previous owner of my flat is a builder and I'm not sure whether he did that or not... :-(

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I know the previous owner of my flat is a builder and I'm not sure whether he did that or not... :-(

I've seen plenty fitted by people who should know better.

 

[diamondgas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Thanks to clarify this but what's the purpose to have one then if this is not a good idea? I'm just trying to understand it.

It's a 'lazy man's' way of not having to drain off the bucket of water in the header tank!! BUT can cause all sorts of grief if inadvertently closed and left that way!! It also closes off the means of accomodating system water expansion so therfore the open vent pipe has to take over its roll!!

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

So does it mean the cold feed is used in conjunction with TRVs of radiators to control temperature?

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It's a 'lazy man's' way of not having to drain off the bucket of water in the header tank!! BUT can cause all sorts of grief if inadvertently closed and left that way!! It also closes off the means of accomodating system water expansion so therfore the open vent pipe has to take over its roll!!

It sounds scary but thanks for explaining this!

 

[diamondgas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

So does it mean the cold feed is used in conjunction with TRVs of radiators to control temperature?

What's your concern papaya?

Your pictures show a close coupled feed and vent and a concern regards the pump getting cold water drawn through it!! The set up is asking for trouble with the potential for ingress of 'fresh' water, it being 'close coupled' ...

What's your concern though? TRV's have nothing to do with the header tank!