On 2007-05-29 16:33:11 -0400, "HeyBub" said:

Michael wrote:
We have an old AO Smith 40 gallon gas water heater which seems to have
some leakage issues.

We have been anticipating replacing it for some time now but I need
some advice.

There are five of us in the house (including my 15 year old daughter,
who takes very extended showers!)

The current unit seems to poop out after 2 or 3 showers and we will
not run the dishwasher or washing machine in anticipation of
showering.
For a new unit, should we go with a larger unit (75 gallon) or are we
better off with a smaller 50 or 65 gallon with a faster recovery time?
What about the "instant," tankless water heaters?

What gives the best performance, balancing efficiency and hot water
availability?

You may be trying to solve the wrong problem.

Replace the shower head with a hand-operated sprayer on a hose. Then
everyone can take a "Navy Shower:" Wet, lather, rinse. Total water usage,
1.6 gallons.

Unfortunately my daughter has been blessed with a head of THICK, CURLY,
LONG hair...just the shampooing portion takes a while...then there's
conditioning, etc.