Hey I am wanting to take off a radiator for decorating. I know to turn the valves off at both sides to do this. However I know some times these valves can pass. Before I have capped the valve if this is the case by putting a pice of 15mm copper into it with a nut and olive on and then a cap end. However the rad valve seems to be 3/4's on this rad. Is there any way of capping these type of valves incase they are passing?