When taking a shower hot water goes away for about a minute or two and then comes back. It starts out hot and goes for about 5 minutes and then all of a sudden gets ice cold.

SOURCE: water only stays hot for 5 minutes when I take a shower

Unit needs a new "dip tube" It is cracked and allowing cold in water to mix with all hot water resulting in "lukewarm water". Need plumbing skills to change out at cold inlet top of heater,pull out old,buy new at hdepot 5.99 reinstall.

Please rate Thanks

jj505

SOURCE: Bosch AquaStar 125b ng suddenly goes cold during shower

Does it happen to any other fixture? If not, it's most likely your shower valve and not heater.

SOURCE: rheem tankless water heater error code C4 13??

check diaphrapm valve or micro/switch best of luck

SOURCE: The hot water shuts down for a few minuts then

your unit is undersized or you do not have enough gas supply to run the unit properly.
If you have to many water features running or you have to many gas items turn on at the same time it can cause problems.

SOURCE: My oil fired hot water

It sounds like your thermostat on the water heater isn't working properly. try turning it up higher and if this doesn't work I would have a service techy look at it.