generally . no , they dont have the btu's necessary to keep up,
a long shower or several huge laundry loads , could deplete it , and catch up
time would be neccessary .

Tankless water heaters on the other hand , can keep up with demand as they are
designed for this ,
pros, you dont have 40 -50 gallons of water being kept hot all the time,
you always have alll the hot water you need ,
you will realize enrgy savings !!

cons , about twice the cost of normal tank water heaters
they need to be mounted on an outside wall . for purpose of venting



"Robert11" wrote:
Hi,phHave a gas fired vertical tank hot water heater for the house.
Relatively bnew unit.85Question: if wife takes one of her infinitely long
showers, are these units 8(typically) supposed to have the heating ability to
keep the flowing water 4at the set point temperature as the hot water flows
out, and the new cold water flows in ?4cOr, must one typically just stop
using water to give the tank a chance "to 5catch up" ?36Thanks,aBob