Adding a new rad, draining a sealed system

[SwitchTheElectricsOff]

Hi everyone

I'm adding a new rad in our upstairs wc on the 15mm pipe (only 2 rads attached to it), I was looking at either freezing the pipe, or draining the system, and think I'll drain the system and re-fill.

Unfortunately I've only drained a gravity fed system - no experience on a sealed system so am unsure what I need to do, and wondered if the group experts can help me!

I've attached photos of my boiler with all kit around it - eventually this will be boxed in when I eventually do my kitchen :S

Apologies for the embedded images, I have no idea how to do a link to the album!

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[Iamchamps]

Turn off all valves on all other radiators and use drain valve probably down stairs on a radiator to drain below the point you wish to add new rad. Install new rad and then repressurise. Don’t wast money on a freeze kit for such a simple job.

 

[SwitchTheElectricsOff]

Thankyou for the advice

I've had a nose around, the only drain point I can see is under the black magnetic thing beside the boiler, above the magnetic thing there is an isolating valve, should I leave that how it is?

A couple of questions (so I understand what I'm going to do)

• Why do the rad valves need to be switched off?
• Do I need to add inhibitor afterwards? If so, what joint should I be looking for to put it in?
• Are there any gotchas based on your experience I should watch out for?
• Do I need to switch off the main water supply, or because it's on its own separate system I don't need to?

In terms of the process, do I do this:

1. Switch off c/heating section of boiler
2. Plug pipe in to the outlet I can see
3. Close the rads off (most of them have been taken off upstairs due to decorating)
4. Let loose with the water outlet
5. Have a cuppa
6. Cut my 15mm pipe, whack in equal tees (I've got compression fittings)
7. Cap them off above the flooring ready for my rad
8. Close off the tap thing
9. Somehow re-fill the heating system
10. Grab a pizza

Turn off all valves on all other radiators and use drain valve probably down stairs on a radiator to drain below the point you wish to add new rad. Install new rad and then repressurise. Don’t wast money on a freeze kit for such a simple job.

 

[endecotp]

I've had a nose around, the only drain point I can see is under the black magnetic thing beside the boiler

Keep looking. I found my drain valve under the floorboards in my spare bedroom, cleverly connecting to an overflow pipe that drains outside, but entirely useless because I’m sure no-one knew it was there.

If the boiler is downstairs and you’re working upstairs then yes I guess you could drain from the filter.

Why do the rad valves need to be switched off?

This keeps the water in the radiators so that you only need to drain the contents of the pipes.
One advantage of that is that the inhibitor chemical is only diluted when you re-fill, not completely removed, so you probably don’t need to add any more - at least not every time you do this.

Do I need to add inhibitor afterwards? If so, what joint should I be looking for to put it in?

If you decide to do this, as you have a magnetic filter you may decide to put it in there; I find it the most convenient point in my system but others may have other preferences.

Are there any gotchas based on your experience I should watch out for?

Roll back the carpets and prepare yourself with towels, buckets, push-fit stop ends and a spare person and ... nothing will go wrong.

Do I need to switch off the main water supply

No.

 

[polesapart]

Somehow re-fill the heating system

You're aware, of course, of the filling loop kindly provided for this purpose and clearly visible in pic3?

 

[McCombi]

You can use the filling loop on boiler to drain the system. You wouldn’t have to drain all of it’s just upstairs needing drained.

Disconnect flexible hose from filling loop then open valve on right side of loop and water will drain out, open vent plugs on upstairs rads to assist draining until drains below bottom of pipes upstairs.

 

[SwitchTheElectricsOff]

Aye yes

For some reason one of those filling valves is open, whilst the other side is closed, shouldn't both be closed? I know it's a dumb question, but if you don't ask, you'll never know!

You're aware, of course, of the filling loop kindly provided for this purpose and clearly visible in pic3?

 

[SwitchTheElectricsOff]

I didn't think of that, that's quite logical thinking! So I make sure the mains water end is properly closed and then literally just open the other and drain whatever is left?

Above the black magnetic box, I have a turn valve, should I leave that open or close it? I have no idea what it really does, I assume it's either pushing water up, or receiving return from the c/h? In which case, a follow up question (if I may) where on earth is the tap hot water pipe?!

I wish I had infrastructure plans of this house

You can use the filling loop on boiler to drain the system. You wouldn’t have to drain all of it’s just upstairs needing drained.

Disconnect flexible hose from filling loop then open valve on right side of loop and water will drain out, open vent plugs on upstairs rads to assist draining until drains below bottom of pipes upstairs.

 

[endecotp]

where on earth is the tap hot water pipe?!

Looking at the bottom of the boiler in your third photo, the pipes are from left to right:

Condensate drain
Central heating flow
Tap hot water
Gas
Cold water in
Central heating return
Pressure relief outlet

 

[SwitchTheElectricsOff]

Thanks for that, I'm going to find a manual and label each one, with what way each flow goes, at least it's a better one than my really old vokera boiler

Looking at the bottom of the boiler in your third photo, the pipes are from left to right:

Condensate drain
Central heating flow
Tap hot water
Gas
Cold water in
Central heating return
Pressure relief outlet

 

[SwitchTheElectricsOff]

I've opened up the flooring, and can see the following pipework

I put the CH on and noted that the green is hot, and the silver is cool.

So I presume the green sandpaper pipe will go into the inlet of this infamous rad, and the return to the silver sandpaper pipe?

The 22mm stuff, one of those is hot, I can't track it as it's going along the joists, we used to have a water tank in the loft (now removed, shoddy workmanship though) so assuming it's going up there and returning back down for something, the OH said she might have had the hot water on in the sink in the downstairs kitchen she can't remember...


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[endecotp]

I put the CH on and noted that the green is hot, and the silver is cool.

So I presume the green sandpaper pipe will go into the inlet of this infamous rad, and the return to the silver sandpaper pipe?

It may not matter which way around you connect them; many valves are bi-directional.

 

[SwitchTheElectricsOff]

Didn't know that - thankyou! One thing I did notice is there is an existing equal T between the green/silver going downwards, I've been trying to see if I can find their route, but it looks like they are going into a false block in the kitchen.

At the moment, does it look like I'm going about it the right way? I'm supposed to be starting to study plumbing in Sep so this is all good experience for me

It may not matter which way around you connect them; many valves are bi-directional.