A few guesses, since I can't see that clearly from he
Assuming it's a gas heater.

"back draft" (downflow in flue) with pilot-only simply indicates
negative gauge pressure in house- maybe from exhaust fan(s), or
chimney-effect in whole-house. With burner on, exhaust is not vented-
a major safety problem. I'd suggest you call the gas company, and
make sure.

"poor rate of rise"? Ask him what he means by this. (Did he use a
thermometer and stop-watch? Not bloody likely.) Ask the gas company
what your recovery rate should be, given the water capacity and input
rate. Ask gas co rep how that compares with "rate of rise", in
writing if possible.

More important, most water heaters are guesstimated to have 10-year
lifetime, so you might be best off to just replace heater- what else
could the buyer be angling for? Better efficiency, peace-of-mind,
happy buyer, better safety in case of combustible fumes, etc., etc.
And check on stack draft, besides.

Heater and installation are so inexpensive, it's a waste of time to
quibble in the context of a house sale.

Tack on a few bucks to the selling price, and everyone's happy. Or
.... knock off a couple against purchase/installation, and let her/him
do it later.

John

"Les" wrote in message ...
I am in process of selling my home. It has a 20 yr old water heater that
has seems to work just fine for me. There is no rust, no leaks, and the
temperature of the water is plenty hot when I need it.

The buyer's home inspector has just indicated that "water heater has slight
back draft and poor rate of rise" and buyer requests this to be repaired
prior to closing. What is he talking about? How significant is this?
(also costwise) Is it something worthwhile repairing, or should water
heater really be replaced?