"Hi, lately it seems as though there's barely enough hot water to take a
shower. I went downstairs to observe the hot water heater...
-There's no sign that the water heater has 'blown up' like seems to
happen whenever my dad's water heater expires
-The heater has the date 1990 on it, which I presume to be it's
installation date.
-The heater is natural gas. I didn't notice any smell... -The heater was
warm to the touch
-It hasn't been very cold here lately.
Do these things just fade away? Or do they always go out with a bang?
How do I assess the situation?
Thanks
Steve"

Bear in mind that as the ground temperature becomes colder, so does the
incoming cold water to the house. This takes the water heater alot
longer to heat the water up to its desired setting. Further, if your
hwh is a 1990...you can figure after 15 years of usage, that, there is
alot of sediment in the bottom of the tank which is displacing water
thus making your water heater of lower water holding capacity (IE : a 37
gallon tank instead of a 40 when it was new). Due to its age, it has
reached the end of its life., and, you are wise in changing it out asap.