I would tend to believe and lean to what ijustluvit is saying. Those are the same units I installed.
Cassie, you did not say weather your hot water tank is gas or electric.
If gas, has the bottom of the tank ever been drained, to get any accumulated sediment out? It settles on the bottom and creates a barrier between the flame and the water.
If electric, if one element (there are two) burns out, then that one element works twice as hard, and cannot heat up that water efficiently.
Although I've seen some water heaters last 40 years...(really!!) Most have a lifespan of 10-15 years or so. Where there is really bad water, much less. I have a friend who actually replaces them every two years!!
The size depends on the load. how many people? Teenagers count as two
.....I would think that any house in TV, with usually two people, a 40 gallon would be fine. the newer units, (if you buy a higher priced one) have quicker recovery rates and better insulation....they will be more energy efficient then the older ones.
I'm just not that familiar with the way Florida water is......your cold water is already much warmer then our cold water is up north. having all the pipes under your slab is a bummer...i'm used to basements where I can work on any portion of pipe. It seems to take forever you me to get hot water to my kitchen sink....drives me nuts. I'm not used to that.
My hot water tank in my Florida home is now 15 years old. I'm thinking of replacing it this May when I'm down there with a new one. I want to do it MY way on MY time, rather then having a neighbor call me telling me it is leaking when I'm still up in NY. I also think I will install a small 110/4 or 6 gallon point of use water heater under my kitchen sink so I do not have to wait forever. I wish I could replumb everything down there...I would plumb a return line back to the hot water heater so the continuous loop would give me instant hot water always.......but I'm not going to bust up concrete to do it.
Carrie, let us know how you make out. Hope this info helped.
Frank D.