persume you are replacing //adding radiator and unable to move pipework that you are teeing into therefore you have purchased slide coupling when using this fitting cut the connecting pipework so that it is as colse as possible make a mark on the pipework so you can see how far the fitting has to be moved into central position the trouble you will find with push fit is that they are large fittings and when you are working in a tight space it can be difficult,you can use plastic pipe and fittings on heating systems and they will stand up to presuresd required however do not use within one meter of the boiler for safety reasons if boiler overheats
tony tsp heating, July 2007