Hot water problems

[Need-help]

When I turn on my warm / hot water from the tub faucett, it works - but only for 4 minutes and then turns cold. I have a Rheem water heater and it's only 1.5 years old, so I can't believe it has to be replaced. I've noticed the force of water pressure from that faucett is very great and thought "is the pressure too great that it empties out the hot water supply from the tank in four minutes?" In addition, I checked the hot water unit's troubleshooting guide where it states that the cause may be low gas pressure supplied to the unit OR a defective combustion system.

Are there valves I need to check to remedy this problem. If so, what & where are they? Could it be the water pressure and, if so, how can I adjust this? Please help point me in the right direction to a fast & easy solution (if possible). Thanks!

[LazyPup]

Unless we are talking about an extremely small water heater (25gal or less) I don't believe the problem is the water heater.

A tub spout is rated for a max flow of 4gpm therefore running the shower mixer to the tub spout would consume 4gpm x 4 minutes for an average of 16galllons.

Considering that this house is only 1.5 years old I would be more inclined to believe you have a thermostatic anti-scald mixer on your tub and it is not functioning correctly.

[Need-help]

The condo is 18 years old and the water heater is 1.5 years old with a 30 gallon capacity. Could it be that the water pressure needs to be adjusted / lowered?