You're supposed to test the valve once in a while, along with checking GFCIs.
I never have checked the valve because if it's opened temporarily for the test and it doesn't fully close, this could be a problem.
So I'd do this test in the morning of a day when plumbing supply stores are open, if I ever do it.
And the drain valve at the bottom of your heater should be the gate valve type so it doesn't obstruct the blobs of minerals that may collect the bottom of your heater and will not want to come out with a regular valve, see "doesn't fully close", above.
Last edited by Wuzzat?; 07-22-2014 at 05:52 PM.