Air pocket.......air pocket....air pocket
Water can not be compressed...........air can be compressed
No air pocket.....PRV weeps

nomad297 wrote:
Now, if your temperature is at or above 210 degrees, there's nothing you can do except have a professional service it, but for the short term, work out which fuel mode (electric, gas) is causing the high temperature condition and make sure the heater is set to the mode that will not overheat the water. Hopefully one or the other will work properly.
Sure there is......replace the set of t-stats.
Normal t-stat should stop heating at 130*F or 140*F
AND the ECO (High temp t-stat) should shut down heating (if normal fails) at 170*F or 180*F (depending on which brand of water heater)
That is IF WH is overheating and not just LOSS OF AIR POCKET