We have new construction. There will be a concrete slab. I dont want to go through the attic space to go from the hot water heater to a bathroom across the hall. The bathroom wall will accommodate a 4" vent so there will enough room. My question is there some kind of flexible supply lines I can run from the utility room (where the hot water heater is) through a 4" secondary pipe under the slab ? I want to do this if I can just in case there ever is a leak. Is there such an installation procedure ?