Question about changing the taps on a boiler filling loop...

I need to change the boiler side tap on the filling loop of my gas boiler. I changed the feed side tap a few months ago and now the second one has gone too.

The question I have is this...

If I remove the boiler side tap from the filling loop will it drain the boiler system or is there some sort of non-return valve that means I can just unscrew it and fit a new tap?

Cheers for any help on this.

Usually the non-return valve is built into the valve itself, therefore you will need to drain down the system to change. I have a freeze machine to freeze the pipe but that is not much good to you.

OK... so it just got a bit more involved....

How do I drain it down? Its a Baxi 35/80 if that makes any difference.

There should be a drain valve somewhere on the system. Usually at it's lowest point.

If the valve can function open, then you only need to attach a new valve to the old one without draining down, i.e. leave the old valve in situ & leave in the open position, turning off at the new valve.