How to drain combi boiler?

alexeix · 21 Mar 2015

Hi All,

I have a Worcester Bosch Greenstar 24i combi boiler and I had a scale inhibitor fitted one year ago, after the plate heat exchanger scaled up, only 2 years after the boiler was installed.

Unfortunately, I didn't check the installation of the scale inhibitor and it seems that the plumber didn't install isolation points on either side of it.
I didn't ask him to, but it strikes me as common sense that you would.
So, I now need to replace the inhibitor cartridge.

How do I empty the boiler?

All the information I've found on the web is about draining combi boiler heating systems, which I don't want to do.

I just want to make sure that I can remove the old cartridge without a load of water emptying out of the boiler. Obviously there will be a small amount from inside the cartridge.

Can anyone point me to any web sites with information/videos please?
Thanks!

Gasguru · 21 Mar 2015

You may have a plastic cover under the boiler that will just slide off to expose the valves.

Under the boiler you will see an isolating valve on the cold inlet...it's the second one along from the right hand side. Turn it a quarter turn and check a hot tap to ensure it's off.

Now turn off the mains stopcock and open a cold taps to confirm it's off.

Hopefully that should isolate sufficient to replace the cartridge.

alexeix · 21 Mar 2015

Thanks for the reply.

The pipework is all exposed under the boiler - I've attached photos.
I think you mean the brass fitting with the 'screw' inside (first picture) - I need to turn that clockwise by a quarter of a turn?

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Gasguru · 21 Mar 2015

No, the the slotted spindle inside the black surround underneath.

alexeix · 21 Mar 2015

Gasguru said:
You may have a plastic cover under the boiler that will just slide off to expose the valves.

Under the boiler you will see an isolating valve on the cold inlet...it's the second one along from the right hand side. Turn it a quarter turn and check a hot tap to ensure it's off.

Now turn off the mains stopcock and open a cold taps to confirm it's off.

Hopefully that should isolate sufficient to replace the cartridge.

Also, don't I need to drain the boiler of existing water?

Would I do that from that from here?:

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Gasguru · 21 Mar 2015

By scale inhibitor do you mean a device on the cold water main?

Post a picture of it.

alexeix · 21 Mar 2015

Sorry for delayed reply - for some reason I can no longer access Diynot.com via Virgin Media.

Here's the scale inhibitor cartridge, although the photo is on its side, the cartridge is actually upright.

Untitled

alexeix
21 Mar 2015
1

Gasguru · 21 Mar 2015

You've isolated the boiler with the valve underneath. There will be residual water in the vertical sections of pipe.

alexeix · 21 Mar 2015

So, I need to turn the isolating valve on the cold inlet by a quarter turn and check the hot tap.

Next, turn off the stopcock and run a cold water tap to check it's off.

Turn the boiler off (probably best to do ths first).

Remove the cartridge and fit the new one.

Gasguru · 21 Mar 2015

Yes but there will still be some water that escapes when you change the cartridge so be quick and have towels underneath.

alexeix · 30 Mar 2015

Thanks - cartridge changed and problem sorted hopefully!

kendo10 · 3 Jun 2017

alexeix said:
Thanks for the reply.

The pipework is all exposed under the boiler - I've attached photos.
I think you mean the brass fitting with the 'screw' inside (first picture) - I need to turn that clockwise by a quarter of a turn?

[/url]

kendo10 · 3 Jun 2017

Hi hopefully you can help, Been hunting all day to find answer to this conundrum Id like to know how you were able to turn the DCW valve screw under the black plastic what I think is a locking ring ? did you remove the ring without damaging it and how? did it replace easily?

Newboy · 3 Jun 2017

A flat bladed screwdriver in the slot and 1/4 turn opens/closes the supply. No need to remove anything.

Edit: If it's hard to turn then don't force it, try an adjustable wrench on it.

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How to drain combi boiler?

Newboy

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