Water Heater Under and Over Performs

[takeitapart2fix]

I have a water heater in my home that seems to be performing erratically.

There are 3 people in our house, and we all take hot showers at different times of day, but mostly in the morning. There is never enough hot water for more than a 5 minute shower.

However, the other day we had 2 guests staying at our house and all 5 of us took showers in the morning (probably 30-45 min apart) and we never ran out of hot water. I would guess that we each got at least a 10 minute shower.

Is there something wrong with the water heater or a part in it? The house is about 15 years old, and the water heater runs on gas.

[rmw]

Is your water heater high efficancy(pvc vent pipe) or standard efficency(metal vent pipe)? What size is your hot water tank? Are you showering with no other water being used or are other appliances using water at the same time as the shower? All this could play into the erratic performance.

To give you a place to start looking with out any extra information I would say you need to look at the thermostat it could be starting to fail in which case you could have plenty when it is working and not enough when it is not.