You seem well versed in the area of plumbing, thank you for your insight and explanations.

Perhaps you can answer for me a question of strategy.

My hot water heater has two propane burners and two small (11-liter each) tanks, the tanks are connected in series so that the first burner/tank preheats the water for the second. This seems like a reasonable compromise all around, with the small tanks reducing the heat loss between usage yet enough of a buffer to handle heavier usage such as showers. It allows the use of smaller burners as well, which may (or perhaps not?) add to efficiency.

The question? How to set the thermostats (each burner/tank has its own) to minimize propane consumption and still provide enough hot water to meet demand. Both at maximum temperature? Both at the minimum temperature that satisfies? Some intermediate setting? Low on the first burner, high on the second?

There are a lot of possible permutations here.

The technicians who serviced the heater last week (new thermostats, new pilot lights, new igniters and new pressure relief valve) just cranked both thermostats to maximum hot and left it at that. Is that the best way to go?

In the next few months I will be adding a passive solar system to pre-heat the water before it goes into the water heater, so perhaps it doesn't matter too much anyway. Currently I am paying $38 a month for propane (cooking and hot water), $7 a month for water, $15 a month for telephone and $16 a month for electricity. With propane accounting for 50% of my total utilities bills, it is the one to focus on.

tanstaafl.