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AR15.COM
2/19/2015 4:55:52 PM EDT
What is the proper method to flush a water heater?

Turn off heat, close inlet valve, hook hose to drain and let it run empty, or

Turn off heat, hook up hose, open the drain valve and let it run till clear......... or

some other method I'm not aware of.

Thanks for the help.
2/19/2015 5:31:59 PM EDT
[#1]
Make sure to turn power off.  Don't want to burn up the elements.

2/19/2015 5:37:57 PM EDT
[#2]
Buy replacement element and gasket.
Turn off power to heater.
Turn off water supply to heater.
Drain water heater.
Remove bottom element.
Use Shop-Vac with a piece of 3/4"-1" tube duct taped into the hose to vacuum out the lime build up.  (Jam tube through element hole in case it isn't obvious.)
Install new element.
Close drain.
Open a hot water tap somewhere.
Turn on supply.
Fill until air stops coming out of the hot water tap and water starts coming out.
Turn off tap.
Turn on power to heater.

Edit to add: if your drain is so clogged that it won't drain, you can backflush it using your cold water pressure.  
Hook up a washing machine hose to a water hose, run water hose to a spigot.  
Connect other end of washing machine hose to drain.  
Turn off cold supply to heater.  
Open a hot water tap somewhere.  
Open drain.  
Open spigot connected to water hose.
Cold water pressure will blast the drain clear.
Now you can drain the heater.

Draining or flushing using just the drain valve doesn't do anything for the kind of lime buildup I get in mine.  Maybe if I flushed it weekly...
2/19/2015 6:43:37 PM EDT
[#3]
Sorry, I forgot to mention it is a GAS water heater. Obviously the steps will be the same minus the element replacement. Thanks for the info!