Best way to drain system

Hello to all you super people, well I have a bit of a predicament, I am in the process of changing a radiator in the upstairs bathroom for a towel radiator. I am scared to death to drain the system as we have been here 18 years and its never been done the system consists of a glowworm boiler, hot water storage tank in the bath room, with a feeder tank above that, then a header tank in the loft. I have heard of way were you don’t have to drain down the system by doing the following put a cork in the header tank feed pipe also in the breather pipe that’s above the header tank thus causing a vacuum letting you work on the system with out water coming out the system….? Can any one verify but if I have to drain the system I have two pipes very near the boiler with drain taps on them would one be for up stairs one for down ?

If the new towel rail fits the existing valve then no need to drain down - just close both valves and drain the existing radiator, fit new rail and Bob's your uncle.

If you need to replace the rad valves or pipework then the two cork system will work providing that you only replace one valve at a time - only have one open pipe other wise you will have an unplanned drain down!

You will still have some water leak out until the vacuum is sufficient to hold the water in the pipework.

Rather than corks you could invest in two rubber bungs made for the purpose - avoids any risk of the cork breaking off in the pipework.

The two drain points near the boiler are likely to be on the flow and return.

Thanks newboy for the reply yes i am changeig the valves so i will try one side at a time...................... if the worse comes to worse flow and return pipes which would i use to drain ?