When a gas water heater doesn’t provide enough hot water, perform the following diagnostics:

1. Turn the thermostat dial to a hotter setting. If the flame ignites when you do this, leave the dial at that setting and then check the temperature of the water in about an hour. To do this, put a meat thermometer into a cup and let hot water from a faucet flow into the cup for about a minute. Then read the temperature.

2. If you don't hear the water heater's burner ignite and/or the water just keeps getting colder, check the pilot light to be sure it hasn’t gone out. If it has, follow the manufacturer’s instructions on how to relight it. Relighting a water heater usually involves turning the water heater's gas valve to "Off" and then to "Pilot." You typically hold down a button, light the pilot, and wait until a status light signals that you can turn the dial from "Pilot" to "On."