I see no reason why you can't.I'm purchasing a house that needs a liner. Oil furnace, no hot water tank. Can I wait till heating season to have it installed ?
If there's no fireplace, you can get a stainless steel liner kit of 30 feet for about $375. and do it yourself.
Who said you need a liner, not the chimney cleaning people I hope.
Not a reputable group in my opinion.