said by nunya:
When I was finished (@ 11:30 PM and 17 trips to Lowe's Depot), I realized the water heater was now blocking access to the A-coil. I said f___-it until a few months ago when it was time to replace the furnace. In order to get the old furnace out and the new one in, I had to relocate that F___ING water heater 12 inches.
A former boss's custom built home had an issue with their furnace. Repair man came and and determined that the water heater was too close to the furnace, like in your case, but slightly different. In their case, it was so close to the furnace that the filter access door could not be removed, let alone the filter replaced. IIRC, they had lived there for 4 or 5 years at the time and never bothered to replace the filter.