I want to attach a garden hose pipe to this 25mm OD male thread on the Rad valve so that I can flush this part of my cental heating system. Any ideas what connectors/adaptors I will need ?
3/4” tap connector to 15mm compression then short bit of 15mm copper pipe. A hose pipe will usually push over a bit of 15mm and can be secured by a jubilee clip if necessary.
Do you already have an outside tap? The connection for your outside tap will probably fit straight on that valve.