Retired plbg1
Are you talking about the angle radiator valve, you mean it is 1″ and your pipe is 1-1/4″. if that is case then you would have to use 1-1/4″ by 1″ reducer and a nipple, you would have to cut pipe. But if you can get below in base ment then take out 1-1/4″ pipe and put in acast iron bushing and run 1″ up to radiator valve, on heating you should use castiron fittings. To sole this go to plumbing supplyhouse and get a valve the right size, you can repack the old valve and buy washers for it at supplyhouse.
