Replacing 3 port valve

[l0ckm4]

Hi all,

I am going to be replacing my 3 port valve this weekend and understand that you need to drain the system down first.

My question is that looking at the piping my pump has 2 isolating valves either side of it. Can i not just close these and then replace the valve and then reopen them? i guess i will get a little leakage but a bucket will be close by!!

Sorry if this is a dumb question.

 

[ollski]

Not unless your feed and vent pipes are between them aswell. If you're feeling brave buy a bung kit when you get your valve otherwise just drain down from a drain point on the radiator pipework to below the level of the valve. Easiest just to turn water supply off completely while doing the valve to prevent tank form refilling.

 

[l0ckm4]

Cheers for the quick answer.

where do i put the bung kit - is it in the expansion tank (the smaller one in the loft) and how reliable are they?

 

[hi-spec plumbing heating]

where do i put the bung kit

don't bother you can't change a 3 port valve by bunging the system.

 

[l0ckm4]

i just found this -

Limitations:
Suitable for 15mm and 22mm pipework.
Not to be used on direct, unvented or primatic systems or auto-vented systems.
Not to be used on systems with a header tank more than 30ft (9 metres) above the systems lowest point.
No lubricating oils to be applied.
Only one section of pipework can be disconnected at a time e.g. No three-way valves - one two-way disconnection only.

does this mean i cant use a bung kit?

 

[ollski]

Cheers for the quick answer.

where do i put the bung kit - is it in the expansion tank (the smaller one in the loft) and how reliable are they?

Yes its the f & e tank, I've never failed with one although it can sometimes take nearly as long to pull a vacuum as it can to empty the top part of the system.

 

[l0ckm4]

thanks hi-spec - i must have been typing when you replied. Ok then - drain the system it is then. Anything i need to be aware of that could go wrong?

 

[l0ckm4]

now i am confused - one saying you cant and one saying they've never had one fail. I think i will play safe and drain

 

[ollski]

i just found this -

Limitations:
Suitable for 15mm and 22mm pipework.
Not to be used on direct, unvented or primatic systems or auto-vented systems.
Not to be used on systems with a header tank more than 30ft (9 metres) above the systems lowest point.
No lubricating oils to be applied.
Only one section of pipework can be disconnected at a time e.g. No three-way valves - one two-way disconnection only.

does this mean i cant use a bung kit?

I've changed hundreds on bungs, if you've got auto air vents shut them.

 

[nickso]

you can change anything on any system using bungs. i cant even remember the last time i drained a system down.....probably more than a year.

ive changed cylinders, boilers and many 3 port valves.

its just a case of how long it takes to get the vacuum. if you are changing a three port valve shut off both pump valves and it should stop the water quicker. shutting the bypass sometimes helps too.

you will probably get approx a bucket of water out of it.....maybe more maybe less.



edit...i lie....i drained my own system down 2 months ago when i replaced all of the pipework....dont try that on bungs