Replacing a 3-way valve

[OJ]

but ya need to close 1 of the pump valves as well!

What? and where?

 

[gas_man_gaz]

ya pump should look like this and will have a valve at either side

http://cgi.ebay.com/GRUNDFOS-UPS-15...oryZ3191QQrdZ1QQssPageNameZWD2VQQcmdZViewItem

 

[ollski]

but ya need to close 1 of the pump valves as well!

You don't.

 

[OJ]

So much conflicting advice......

 

[AlanE]

So much conflicting advice......

Thats true but you must remember those that regularly change these valves, and I am one of those, have their own favourite methods. None are necessarily right and likewise none are necessarily wrong! Just different ways to the same end.

Most pros will look at the job in hand and decide what way would be the quickest in THAT situation it is not a case of always doing it the same way. I might drain down part of system, use bungs or if the pipes are cold might use the freezer and save the hassle of air locks. It all depends.

 

[Softus]

OJ - ignore all of the advice about bunging etc. The first time you do this work you'd be better off draining so that you can concentrate on the relatively difficult bit.

Your idea of replacing the frozen valve part is fine. However, you would have been better to have bought the entire valve and at least kept the actuator head as a spare, because the electrical and mechanical components of the head would have been strained by the frozen valve.

Anyway, your proposed sequence of steps is nearly perfect. Some comments on your questions...

1 - tie up the ballcock in the main tank (or the f&e tank) in the loft

I would just shut off the water supply to the F&E cistern, not the main tank, if the former has its own stop cock. If it doesn't then shut off to the whole house - it will only be for am hour or so.

Is there a valve on the hot water cylinder?

You don't need to drain the HW cylinder, and it would be unwise to open any drain off cocks near the cylinder.

4 - how do I kow when the system is sufficiently drained, other than by starting to undo the connection on the old 3 way valve?

Water will stop coming out of the end of the hose.

do I use boss white, ptfe, or?)

Personally, I use PTFE. If there is paste on the pipework then remove all traces of it first. The wind about 4 turns of tape over the wet side of the olive, and not on any threads.

6 - shut off the drain valve, and any open bleed valves.

I would always replace the washer in the drain off cock - when they're old they can harden and break up.

7 - add some (how much?) inhibitor (fernox?) to the tank in the attic, and untie the ballcock, to allow the system to re-fill.

Do one fill without the Fernox first, to (a) check for leaks and (b) check that the system actually fills - some dirty systems can form a blockage that prevents, or delays, them filling.

8 - bleed all rads (start downstairs, or doesn't it matter?)

It doesn't matter. On the final fill, i.e. with Fernox, it doesn't matter because you'll have to vent them again after a few days.

9 - fire up the boiler, and check that the switching works correctly.

Yes, but be absolutely sure that you get water from the highest rad vent first.

 

[gas_man_gaz]

but ya need to close 1 of the pump valves as well!

You don't.

it works beta if ya do!

 

[ollski]

but ya need to close 1 of the pump valves as well!

You don't.

it works beta if ya do!

it don't

 

[gas_man_gaz]

but ya need to close 1 of the pump valves as well!

You don't.

it works beta if ya do!

it don't

hmmm, i should say we'll hav to agree to disagree... but it does

 

[ollski]

The more volume of water you try and bung the quicker it holds, like the way 28mm is much easier and quicker than 15. Must confess I have never tried to bung the same job 2 different ways to compare though. I use an old smoke bomb tub to catch the water and it has almost never got more than 2 thirds full before the bungs hold so I do't think I will start turning off valves and risking leaks for an improvement on that.

 

[gas_man_gaz]

brave man ollski, i always use a rubble bag to catch the water - gives me a bit of time if it does go wrong!

 

[OJ]

OJ - ignore all of the advice about bunging etc. The first time you do this work you'd be better off draining so that you can concentrate on the relatively difficult bit.

Your idea of replacing the frozen valve part is fine. However, you would have been better to have bought the entire valve and at least kept the actuator head as a spare, because the electrical and mechanical components of the head would have been strained by the frozen valve.

Anyway, your proposed sequence of steps is nearly perfect. Some comments on your questions...

1 - tie up the ballcock in the main tank (or the f&e tank) in the loft

I would just shut off the water supply to the F&E cistern, not the main tank, if the former has its own stop cock. If it doesn't then shut off to the whole house - it will only be for am hour or so.

Is there a valve on the hot water cylinder?

You don't need to drain the HW cylinder, and it would be unwise to open any drain off cocks near the cylinder.

4 - how do I kow when the system is sufficiently drained, other than by starting to undo the connection on the old 3 way valve?

Water will stop coming out of the end of the hose.

do I use boss white, ptfe, or?)

Personally, I use PTFE. If there is paste on the pipework then remove all traces of it first. The wind about 4 turns of tape over the wet side of the olive, and not on any threads.

6 - shut off the drain valve, and any open bleed valves.

I would always replace the washer in the drain off cock - when they're old they can harden and break up.

7 - add some (how much?) inhibitor (fernox?) to the tank in the attic, and untie the ballcock, to allow the system to re-fill.

Do one fill without the Fernox first, to (a) check for leaks and (b) check that the system actually fills - some dirty systems can form a blockage that prevents, or delays, them filling.

8 - bleed all rads (start downstairs, or doesn't it matter?)

It doesn't matter. On the final fill, i.e. with Fernox, it doesn't matter because you'll have to vent them again after a few days.

9 - fire up the boiler, and check that the switching works correctly.

Yes, but be absolutely sure that you get water from the highest rad vent first.

Many thanks indeed, for your help, Softus.

OJ.