Hot water in bathroom 20 degrees colder than water heater

[miamihoosier]

I have been chasing a lack of hot water for a couple of years in my new house. My plumbing installer passed away. I've just been trying to figure it out myself. Anyway... I have a standard water heater set to 120 degrees (small children in the house). All of my piping is copper. My line runs vertical for three feet and attaches to my main hot water line. It tees. To the right, it runs to my kitchen, about 15 foot run where the temperature is almost 120 degrees out of the faucets. To the left it runs to the rest of my house. Farthest run is about 30 feet to my master bath. The hot water coming out of my faucets in the showers or sinks attached to this run is 97 degrees, regardless of how long it runs. There is no plumbing on any outside wall. It all runs above my head in the basement. I have inspected the plumbing many times. I can not see any obvious error in its installation. I am on a well and run my hard water through a water softener before it goes to my hot water heater. I do not remember the brand of my kitchen faucets, but they are not Delta. All of the faucets with the "colder" water are either Delta centermount faucets or Delta shower faucets with the round control for hot to the left and cold to the right. Could one faucet be backfeeding cold water into the hot water line? In my master shower I do have two valves, mounted side by side. One feeds the main shower head. The other feeds the overhead shower head. Any feedback to ideas for troubleshooting this issue would certainly be appreciated. Thanks!

I do not have a re-circulation pump/system. I am not aware of any one-way valves in my system which could be sticking.

 

[phishfood]

Turn off the water to both of the sink faucets, then test the shower valve. Also, test the temperature of the water coming out of the hot supply valve under one of the sinks and see what you have there.

 

[miamihoosier]

Great idea to turn off all the faucets and start from the beginning! I did that and started testing. My temperature out of my spa tub started at 130. I've never seen that before! It did drop quickly to 112. I started thinking that maybe I had a hole in the dip tube. I have checked and re-checked the elements. They always check good. I pulled out the dip tube. Great shape. I put an amp meter on the top element. 18 amps, or so. Perfect. However it flickered. Now 2 amps. I shut it down and pulled out the element. There was a pinhole in the element. I could wiggle it around and change the resistance. Now I have two new elements installed. Both thermostats check perfectly. Tomorrow, I'll see what the temp is and start my quest again to see if I do also have a faucet problem.