Inconsistent water heater?

[e rock]

Water heaters are one of the few things I've never taken apart to see how they work. It seems like a simple enough concept, but maybe there's something I don't get that explains this...


Whenever the hot water doesn't get used for an extended period of time (like at least a day or two), there seems to be very little available, and not as hot as it should be. After running the hot water for a bit, everything will be back to normal within an hour.

For normal day-to-day use, there has never been a problem. The thermostat works just fine for regulating the temp during normal usage patterns, and I've never noticed any other anomalies.

It doesn't bother me, except that when we come home from being gone for a few days, my wife will be drawing a bath before I've even got the suitcases in the door. When the bath only gets half full before the water starts running cold, somehow it's my fault, so here I am.

It's natural gas, 50-gallon, roughly 6 or 7 years old. Our water is very good, no excess minerals.


One person mentioned something about the "dip tube"? If that sounds like a reasonable culprit, would someone mind explaining?

 

[Toyo FJ40]

Dip tube runs the cold water to the bottom of the tank without it mixing with the hot. The hot water floats on the cold water because the cold water is denser. If the dip tube fails (AO smith and Bradford White both had bad batches of dip tubes about 5-6 years ago) Then the cold water entering the tank will mix with the hot water and there will be fluctuations in the temperature because some of the cold water is being pushed out the hot pipe and some is mixing with the hot.

The dip tube is a plastic tube that sits in the inlet (cold side) of the tank. On bradford white they sit in the die-electric nipple. On AO smith they sit in the threaded inlet of the tank.

 

[KLF]

I had a kinda similar problem with a State propane-fired water heater in my last house. It was like the thermostat was "lazy" and wouldn't fire the burner when the temp got to the low temp point, and the water in the tank wasn't hot enough. Usually the first shower of the day was lukewarm, then if you waited an hour or so there was plenty of hot water. If I knew I was gonna be taking a shower and the thing hadn't cycled recently, I would run down to the basement and tap on the big temp setting knob a few times and sure enough it would fire off and start heating water.

The thing was still under warranty, so I complained to the place where I bought it, which fortunately was also the place that delivered my propane, so they came out and put a new thermostat on it for free. It was much better for awhile, the started with it's old habit again, but by then it went out of warranty. Then I sold the house.