What would cause a pilot light in a gas water heater to blow out repeatedly?

Every time I light my water heater it lights the burner heats the water but soon after goes out. I usually light it before bed so I can take a semi hot shower but every morning it is out. I was hoping someone could offer some advice so I could try fixing it and not have to call a plumber to do it. I wouldnt be so upset about it but its less than a year old so Im hoping its something simple.

As a couple of others have stated, the most common cause of a pilot light going out, is the thermocouple. Its a relatively inexpensive part, and not too hard to change out.

You mention this was less than a year old though...
Did your installer run a new exhaust vent through the roof? If so, they may not have gotten the stack tall enough, and you could be having a down draft blowing the pilot light out.

One other cause, could be a central air system...Ive seen a couple of cases where a fresh air intake was cut off to the HVAC system, and it literally sucked air down the water heater exhaust vent. That's dangerous because it is pulling the exhaust fumes right back into the home. That's easy to check for though, by placing a carbon monoxide detector in with the water heater. If it goes off, your exhaust fumes are being pulled back into the home, either because of a vent stack the wrong height, or the HVAC pulling it back in.

A less likely cause would be the gas valve on the unit acting up, or air in the lines. You'd only have air in the line if some work had been done recently (replacing pipes, etc), and would be temporary.

The thermocouple is probably the least expensive thing to replace, so you might start with that. I'd suggest actually taking the old one off, and take it to the store with you, to get a matching replacement. At the very least, take your brand name, and model number with you. Some hardware stores carry these, and most appliance stores.

Good Luck

If the pilot looks "healthy" its probably the thermocouple. The thermocouple is the copper or aluminum tube which leads from the gas valve to the pilot assembly, in which the pilot flame impinges on. Length is what you go by to get a replacement as most come with a variety of mounting hardware.

If its less than a year old, it should still be under warranty. Might check your paper work that came with it.

I do agree with the other person, it sounds like the thermocouple has gone bad. They are not costly and if you are handy at all, you can probably change it out yourself. You can buy them at any home store, hard ware store and some big places like Walmart.

a draft from somewhere