The tenant called to say it wasn't an emergency; he had the temperature on the water heater all the way up and they were getting good enough showers with all hot water and just a little cold water to keep it from burning. The water heater is so blocked up with hard-water residue that only a tiny bit of water is actually heating and getting to the house.
So I got after it! I called plumbers and my husband. I went to Lowe's and 2 Home Depots. I got opinions about the building code. I Googled the building code.
The question was about where the line from the new drain pan should empty. The heater had been upgraded to code in 1998 by a plumber, but it didn't have a drain pan. The current code definitely calls for a drain pan. The drain pan is a simple pan that goes under the heater, but it holds only an inch or two of water. It has a plug that attaches to PVC piping so that if more than a small leak occurs, the water will be carried away from the heater and the house.
The tenant said he'd install the heater and end the drain line where the air-conditioner condensation line is. An Inspector who works at Home Depot said it can't drain there, and that if we did that, when it comes time to sell the house, the Inspector will note it and the buyer will make us fix it to code or pay to have it fixed.
The plumber said the pan needs to drain outside, ie, the plumber will install the water heater and run the drain piping to the wall and drill a hole through the brick wall of the garage so the water can drain outside for approximately $800.
Another Home Depot salesman who is also an Inspector called his boss for me. His boss said the drain line can end over the edge of the little step in the garage (just a few feet from the water heater, which is on the little step). This way, in the unlikely case of any overflow; the water would drain onto the garage floor, which is slanted toward the driveway.
The code says the pan drain must "...terminate over a suitably located indirect waster receptor or ... to the exterior of the building." Google says "did you mean waste receptor?"
I phoned the city to help me interpret whether using the garage floor for the potential draining would be OK. The city engineer agreed that we could just end the drain line over the little step. Just so that no part of the inside of the house would be damaged in case of a water heater flood.
The water heater research and shopping took 2 days.