Our 15 year old water heater has been giving us this problem since earlier this year, but the cold fronts we've had in Texas this winter has made it worse enough for me to finally get off my lazy butt to attempt to fix it :p

Shower provides hot water at the proper temp, but turns lukewarm only after ONE ten minute shower.

My initial guess was the thermostat or heating elements, so I tried out this really helpful guide to diagnose : How to Test a Water Heater Thermostat - wikiHow (http://www.wikihow.com/Test-a-Water-Heater-Thermostat)

Screenshot of the water heater:
http://i254.photobucket.com/albums/hh114/nugentoffer/misc/HPIM1089.jpg

The heating elements measured 13.4ohms , and 12.8ohms for top and bottom respectively. Both thermostats also delivered 240V properly to the heating elements when turning each thermostat on max and making the other minimum temp. I did notice that I could never get BOTH heating elements to be operating at the same time even when both thermostats were set at max temperature, I assume this is supposed to happen?

So now I'm not too sure what the problem could be, as I think the water heater is operating correctly. I currently have set bot top and bottom thermostats back to 130F.

You guys have been really great helping me in the past so thanks in advance for any advice... I'm lost :confused::confused:

Hot water heaters work harder during winter. Your hot water delivery is also effected by non-insulated pipes - and, by type of shower head you are using.

Presently, you have 50gln heater. If you are using 4 gln/m shower head than your timing is just about correct. In fact, it should be even less. If you install water saving shower head, you'll get longer hot showers.

Without looking at it, and with both elements working, I think your heater is fine.

However, plumbing is like health: it is all about prevention. Start thinking about replacing it with energy efficient unit in the near future.

Good luck... Milo

Take a 5 min shower... :)