I have the 40 gal Whirlpool electric.. same problem here, after two minutes (not even 10 gallons) the water gets cold or barely warm with the shower valve all the way to hot.. Very disapointed with Whirlpool.. my old tank was working like a champ before it started leaking.. I recomand Keenmore next time..

Hi Sam and welcome to The Plumbing Page at AskMeHelpDesk.com You are responding to a 5 year old dead thread so I gave you one of your own. Please check the date before you post. Thanks,
Several things could cause this problem.
1. A burned out element **or** And this is what sounds like happened.
2 The installer put too much heat on the cold water inlet and melted the plastic flange on the dip tube allowing the dip tube to fall into the tank.
The dip tube directs the cold water to the bottom of the tank. (see image) where it's heated by the bottom element. If the dip tube fails then every time you make a hot water draw you're allowing cold water to enter at the top and cool off your draw.
Shut the power and water off to the heater and open up the cold water inlet to check the tube. If you have ton replace the tube come off the inlet with a 4" brass nipple before you do any soldering. Good luck, Tom
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