My reliance 606 water heater drain valve is leaking..what size do I need to replace it

Shut off water open lowest drian/ tap off water will run off there .It will take the pressure off

Anode might be leaking ... or water heater is rusted out:
Following link has troubleshoot walk-thru:
http://waterheatertimer.org/Leaking-water-heater.html

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

Sounds like rusted tank gave out:
http://waterheatertimer.org/Leaking-water-heater.html

thermostat.Check Settings,and if you turned it up or down while power was still on, thenchange them both. also t+p valve may be weak from temp overshoot.Change it if it continues after replacing thermostats

No reset button.
The gas control valve is the thermostat
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

Intellivent gas control can be reset, and Honeywell can be reset under some circumstances.
Otherwise, bad thermostat means replace gas control valve

Gene

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

Reliance is AO Smith.
Each gas control has identifying information on side of gas control valve. Make sure you order for NG natural gas or LP propane gas, since these are two different gas control valves.
Google search the gas control number and results will show.
Copy following links for more help:
http://waterheatertimer.org/pdf/How-to-replace-water-heater-gas-valve.pdf
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

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

You have water leak that you can hear running water.
Could be broken pipe under house.
Could be water running out of tank at TP valve.

Turn off all water taps and put ear against each pipe at tank.
If TP valve is leaking, then replace TP valve.
If pipe is broken under house, then call contractor.
Copy following links for troubleshoot walk-thru.
http://waterheatertimer.org/images/Ear-against-pipe-200.jpg
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#listen

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

Reliance 606 240Volt water heater.
This water heater is fully repairable by homeowner

You have some hot water so that says upper element is good.
It also says electricity to water heater is good.
Also your reset button is not tripped. water heater is not overheating.
And covers and insulation are installed properly on water heater.
Water pipes are not clogged, and tank is not leaking water on floor.

Here are the suspects:
1) Leaking faucet or TP valve is running hot water continuously. Check for leaks.
http://waterheatertimer.org/How-to-replace-TP-valve.html

2) Loose wire/ bad wire: remove covers and check for loose wire and signs of high heat and burning.
Also do full troubleshoot:
http://waterheatertimer.org/How-to-troubleshoot-electric-water-heater.html

3) Bad lower element, possibly due to sediment build up: Test element.
http://waterheatertimer.org/How-to-test-water-heater-element.html
http://waterheatertimer.org/How-to-clean-sediment-out-of-electric-water-heater.html

4) Bad upper or lower thermostat: Replace both thermostats for $28.
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html

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 water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

Here is the link for the users manuals for the RELIANCE 606 30 GALLON GAS WATER HEATER, depending on the style you have - tall, short, etc.
http://www.reliancewaterheaters.com/lit/om/g606.html

You will want to use the long shank temp-preasure relief valve.