Hot water heater is leaking from one of the legs. We had turned the water temperature to "vacation" for a couple of days and then turned it back on and there was no water leaking for about a week and then it started again. It is a small puddle about the size of a large dinner plate and it seems to be coming from a leg hole.

Would you please give a little more specifics... but in the mean time check to assure the HWH is not set to "Vacation" temperature level.

I recommend safety changes to prevent ruptured water heater and assorted leaks.
135 degree hot water.
Maybe replace TP valve if it is dripping.
Drip pan under water heater with 3/4" drain line to outside.
Expansion tank on incoming cold water line to absorb pressure build-up, and prolong life of tank and plumbing.

Here's why:

1) Yes you can have scalding hot water.

2) I recommend 135 degrees since that will burn the evil right out of ya. And generally kill clothes washing bacteria.
http://waterheatertimer.org/How-to-adjust-water-heater-temperature.html

3) 150 is dangerous and can seriously burn skin in 1.5 seconds. Not safe around children and elderly.

4) Temperature settings on electric water heater are approximate, since thermostats are calibrated approximately, and read temperature through tank wall.

5) Also if you want to increase amount of hot water for high-consumption household, then setting tank temperature upward is one solution since more cold water is mixed with hot, so amount of hot inside tank goes further.

6) High temperature can cause TP valve to release water.
TP valve is pressure-temperature safety valve. Do NOT cap off.
Rating should be 125 psi and 180 degrees ... but all things water heater are approximate, and TP valves need replacement now and then.
It is not recommended by water heater manufactures to use 150 psi TP valve when water heater came with 125 psi. Rating shows in small print on end of TP. New TP valves sold at local hardware. Let tank cool before installing new one.

7) Higher temperature and high pressure can rupture tank.
Pressure over 80 psi shortens life of water heaters and plumbing fixtures. Put BTG100 pressure gauge on water heater drain valve to check pressure.

8) You need a drip pan with 3/4" drain line to outdoors, or to drain vent line, to prevent flood caused by ruptured water heater.
Turn water heater off when going on vacation.
Inspect water heater each 6 months.
Drip pan available at local home center or hardware:
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html#drip

9) Heated water expands and puts pressure on tank and pipes.
Water does not compress... so when water gets hotter it expands against tank wall and against pipes.
Especially in closed system (check valve present) when system is without expansion tank.
Expansion tank is installed on incoming cold water line.
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html#expansion

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Open following links for possible help:
http://waterheatertimer.org/How-to-adjust-temperature-on-water-heater.html
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Replace gas control valve.
The gas valve is the thermostat.

Vacation setting should be 50 degrees, or so, depending on exact gas control valve.
If gas water heater is not responding to temperature setting, then thermostat is suspect.

Open following link to help identify tank-type gas valve.
http://waterheatertimer.org/How-to-adjust-water-heater-temperature.html
Each gas valve should have identifying number on side.

Instructions how to replace typical gas control:
http://waterheatertimer.org/pdf/White-rodgers-gas-vale-replacement.pdf
http://waterheatertimer.org/pdf/How-to-replace-gas-control.pdf

Additional resources with service manuals:
http://waterheatertimer.org/How-to-install-gas-water-heater.html#troubleshoot

Add a comment for more help.

Take a moment and rate answer for accuracy:
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

Water inside tank-type water heater can remain hot for some time.
That's one advantage of well-insulated tank-type water heaters.
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html

Power outage can be related to failure of gas control.
Unplug stuff when power goes out. And then plug back in after power is restored.
Water heaters with electronics are not protected from surge.
Electronics can blow out during and after power outage. For example nearby lightning strike will cause current to run along household wires. With ordinary power outage, once power is restored, the surge can affect all kinds of electronic circuitry such as timers, water heaters, water softener, treadmill etc.

Sounds like you have intellivent gas control valve:
Open following link to identify gas control, and download typical manual, and download intellivent service manual with troubleshooting, error codes, etc.
http://waterheatertimer.org/How-to-adjust-temperature-on-water-heater.html#intelli

Take a moment and vote on answer:
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

It sounds like TP valve is releasing water, but you don't describe where water is located.
Run through process-of-elimination check list on following link:
http://waterheatertimer.org/Leaking-water-heater.html

1) If problem is TP valve, event could be caused by 'stacking'
Stacking is where you draw amounts of hot water many times in succession.
Top part of heater is plenty hot because water heater is keeping up with hot water draw.
Incoming cold water enters bottom of tank through dip tube causing thermostat to read cool temperature and activate burner or element. This causes higher than ordinary temperatures at upper part of tank and TP valve reacts by releasing water.

2) TP valve could be going bad.
http://waterheatertimer.org/How-to-replace-TP-valve.html

3) Improper venting can cause gas water heater to have water on top of tank or dripping down inside tank where it shows on floor after rusting out combustion chamber.

4) Thermostats are old or not reading correct temperature.
Turn down thermostats:
http://waterheatertimer.org/How-to-adjust-water-heater-temperature.html
Replace gas valve on gas water heater, and flush tank.
http://waterheatertimer.org/Clean-sediment-out-of-water-heater.html
Replace electric water heater thermostats
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html

5) Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, expert speaks with you over phone while you work on heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

There should be a temperature setting on the gas valve. It should be on top or front and have several settings normally vacation, warm and hot. Rotate dial towards hot setting to increase water temperature. Hope this helps. Thanks

Do you have the model number? There is usually a temperature control knob on the heater that you turn to VAC, that just keeps it lit. Usually, setting it to 120°F is adequate.

Hello check the temperature control knob setting. try turning it up.

Do you have an expansion tank tank  in the line leading into water heater? If not what is happening is that the water is no longer allowed to go back into the city supply.  You said that you had turned it off while you left so the water heats up and has no place to go so the preasure/ temperature P/T valve  opens and lets out the excess water from the expanded supply (heater water) that has no where else to go. It used to be that the extra expanded water just backed up into the supply pipe and back into the main. That is no longer possible in most places by the  National Plumbing code.    The answer may be to install the expansion tank into the incoming line. You can see then now at  all hardware stores where water heaters are sold.