I have a.O. Smith gas water heater. When I leave the house for a few weeks (I leave the water heater on, set to the normal temperature) and then return, the water temperature is luke warm. If I run a fair amount of hot water, as in taking a shower, the water heater will then come on and the temperature will come up to where it should be. It has also done this a time or two after just one day. Any suggestions?

Sounds like you have a bad thermostat. Likley the testing could be over your head or do you have some elctrical skills? BTW if you are gone for weeks at a time you can set it to pilot only and save more gas.

Thanks for the reply. I have some electrical skills, so how would I go about checking the thermostat?

Before we start with that have you flushed the heater in the past 6 months? If not lets get that done. Open the drain spigot with ahiose attached and directed to a drain. Allow the heater to flush, leave the main on full, for about 5 minutes or until it runs clear and no spoecs for a minute. This may give you a give all by itself.

Ok, thanks. I'll try that, so it may be awhile until I can tell if it's done anything. What would be the next step?

If flushing the heater fixes your problem you will know in a day. It should go back to acting the way it used to. Where do you have your thermostat set right now?

The temperature is set to "B." I don't know what the actual temperature is, because it's not marked. The water heater has been in use for 6 years and we have had softened water all that time. I've not had a chance yet to flush the tank, hopefully tomorrow.