I'm in the middle of renovating our 19'.  We have taken out all the dinette, water, electrical box and cabinetry.  I'm looking at my water heater and the exterior access has a hole rusted clean through about an inch across.  Is the "flange" that connects the heater to the trailer a replaceable part or is it time for a whole new unit?  It looks like I can replace the whole unit from the outside of the trailer.  Is there any reason why I should do it NOW while the cabinets are out?  Can I patch it and replace it later?  We have a 2000 19 deluxe.  Gas only, I'm assuming it is the same as wat they are still putting in it today.  Atwood G6A-7.  I'm not opposed to replacing it but if it is just a matter of replacing the flange that'd be great.