no hot water only luke warm water after long time

[prem44]

we just got new hot water tank installed in the house. it is bradford & white 40 gallon hot water tank. we set the thermostat all the way high to hot but we are getting luke warm water after running the faucet for a while in the laundry room, bathroom and kitchen. specially in kitchen we get cold water and we have to run it for a very long time (approx. 5 -7 minutes) to get the luke warm water. the hot water tank is producing the water hot but it is not flowing as hot in the house.
any suggestion will be greatly appreciate

[HayZee518]

which thermostat? there are two of them bottom and top. top should be slightly higher than the bottom because hot water stratifies to the top. cold water dip tube goes to the bottom of the tank off the cold water supply. is the heater receiving the full 240 supply? check breaker.

[LazyPup]

Although the post does not state why the water heater was changed out for the moment let us assume that at some point in the past the hot water system was functioning correctly and the water heater itself failed.

A kitchen faucett has a flow rate of 2.5gal/min and the post states it takes up 5 to 7 minutes for the hot water to arrive at the kitchen faucett.

A 1/2" water line contains one gallon of water for every 98 linear feet, therefore if the problems was residual water in the pipe cooling the minimum length of the line would have to be 5 x 98' = 490' to 7 x 98' = 686' long. It is hightly unlikely if your entire hot & cold water distribution system combined has 686' of pipe so we can rule out losses to pipe radiation.

The water heater is the only component in your distribution system that has been changed and the problem seems to be affecting the whole house so we can assume for the moment that the problem is at the water heater location.

The first step is to determine what the actual water temperature in the tank is when the thermostats are satisfied. To verify the internal temperature do not use any hot water for about 4 hours to insure the tank is at its demand temperature then draw about a quart off through the tank drain valve and measure the temperature with an accurate thermometer. This will be enough to get a good reading but not enough to be dramatically influenced by cold water dilution from incoming cold water.

If you have the thermostat set at the "Hot" position as stated the test sample should be in the order of 160 to 180degF. If the temperature tests okay at this point the water heater is working properly and we can rule out a defective thermostate, heating element or burner so the problem must be something related to the installation.

Look carefully at the top of the water heater where the lines connect to the tank. You will see a "C" and an "H" stamped on the top cover indicating to proper posistion of the Hot & cold lines. If those lines are reversed the incoming water will be delivered to the top of the tank and the outgoing hot water would be drawing up through the Dip Tube from the bottom of the heater. Understanding that the cold water from the supply is denser than the hot water it stands that the cold water will settle to the bottom of the tank and dilute the hot water as it exits through the dip tube.

Another possibility is that the dip tube may have been damaged either during manufacturing or installation and the incoming cold water will then take the path of least resistance by passing directly across under the top of the water heater vessel and exit out the hot water port causing the hot water to be diluted by the incoming cold water. If this proves to be the case a dip tube can easily be replaced. (for a new water heater it would be covered under warranty).

Another possibility is that you may have a "Whole House Tempering Valve" that was either reconnected incorrectly, it is out of adjustment or it is not functioning correctly.