CH Drain point on boiler

3 Oct 2017
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United Kingdom
I want to drain the CH system and replace water and inhibitor. There are no drains on any of the radiators, but there is what looks like a drain on the bottom of the boiler. On the attached image look at the bottom of the left hand copper pipe. Only thing is, it's not below the level of the radiators, probably about 6" up from the bottom of each rad (single storey). There's also one rad that's lower than the rest and this drain point is about level with the top of that one.

1. Is it a drain point?
2. How can I get the rest of the water out, seeing as this higher than the bottom of the rads? Do I actually need to get it all out? (Water is clear, no debris, but no idea when inhibitor was last replaced - at least 5 years ago).


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I usually drain just enough water to allow me to add inhibitor into an upstairs towel rail.
Was told you shouldn't mix inhibitor types. As I don't know what's in there I wanted to drain it all and start fresh. Is that not needed? Or shall I just drain what I can and not worry about the dregs?

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