Just like storm windows, a double pipe can keep the weather out, but PVC and steel pipes break in the winter even when they are insulated if they are single pipes. I have seen that pipes of any kind (plastic, steel, copper, etc.) used in any application come in any size you want them in. If you have a one inch pipe then you place the hardly useable insulation over it tightly, then you place a slightly larger pipe over it which provides a pocket of air around the inner pipe which will never...