How to add inhibitor after system drain

[matt1976]

I've got to drain my central heating system to replace the mid-position valve as it has seized.

When I refill it when do I put the inhibitor in?

It's an open vented system, so do I just pour it in the header tank and turn the water on to fill it and let it mix in the system or is there more to it?

 

[Mark Br]

It's an open vented system, so do I just pour it in the header tank and turn the water on to fill it and let it mix in the system or is there more to it?

Yep, just poor it in the tank and refill

 

[45yearsagasman]

Clean out the exp tank thoroughly to prevent dirt entering the system during refilling.

 

[leakydave]

Fill the system and check it is leak free before adding the inhibitor.

 

[matt1976]

Next question is how do I get the valve out? All the pipes are secure and I can't see how there would be enough give to get it out. I'm worried about trying to force something and breaking the tank.

Untitled

• matt1976
• 3 Aug 2013
• 1

Cheer for the tip on filling the system to check for leaks, better than having to go buy more inhibitor. I looked in the tank and thought I might need to clean it.

 

[45yearsagasman]

Undo and remove the rear pipe to the valve. Slacken the union on the cylinder while ensuring the tank boss is not moved. 2 pairs of grips needed there. Once that is done the flow pipe to the cylinder should come out of the valve body after undoing all the nuts. If you are using the same make of valve then the nuts and olives will be reusable. Use a smear of joint compound during refitting.
You'd be surprised on how little movement is required to actually get those pipes out of the valve body. Good luck and be brave.

 

[matt1976]

Is there a specific tool for holding the tank boss or just use an adjustable?

 

[matt1976]

Got it off, cheers.

 

[matt1976]

It's fitted and filled. Just off to buy a radiator vent key as I can't find one as usual.

Should I run the boiler up to temperature to make sure it stays leak free before I add the inhibitor or is that unnecessary? If I do turn it all on, do I need to let it cool down before draining some of the water out to get the inhibitor into the system?

 

[leakydave]

I installed an entire new sealed system once, 22 rads and unvented cylinder. Filled it cold, all well, maintained pressure and no leaks. Waited for electricians to finish...

Week goes by, system wired up, so boiler fired up. Only THEN, once pipes were getting hot did I discover that I had forgotten to solder on 15mm tee in a cupboard and it started to leak like anything...

so yes, best run the system first but a compression fitting onto existing olives isn't really likely to leak...

much!