Need water heater overflow help

IHELP! have been struggling with my 50 gal Bradford White electric hot water heater (approx. 8 yrs old) for a week now. Woke up the other day to find my garage floor soaked and hot water draining out the overflow tube. I emptied and flushed tank, refilled, only for the problem to repeat itself as soon as the water got hot...Note: it has seemed hotter than normal the night before in the sink.
Since then I replaced both thermostats but as soon as I get the electricity back on within 10 minutes the drain tube had a pretty good flow coming from it..not just dripping! And the water is not THAT hot at the point. Do I take it that my next step should be replacing the pressure relief valve? Or is it a blockage in something else? Currently I am cutting electricity on only a few minutes as needed while catching overflow in buckets/tubs. I am attempting to make these repairs without incurring huge bills as I have just had to have both my roof and a/c units replaced.
What should be my plan of action on finding the correct fix? Thanks.
--
broke and fixing it

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broke and fixing it wrote:

Sounds like a bad pressure relief valve. I'd replace it and then see if problem wasn't solved.
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I find that "hotter than normal" worrisome, whatever ever else you do, do NOT plug the valve or cap the pipe attached to it, even as a temporary measure...
http://www.safteng.net/Accident%20Photos/Hot%20Water%20heater%20explosion.htm
and THAT was only a 5 gal unit.
Michael Thomas Paragon Home inspection, LLC Chicago, IL mdtATparagoninspectsDOTcom eight47G5-5668
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broke,
I'm betting that your "overflow" tube attaches to the pressure relief valve. With the water heater off and the water inside it fairly cool open and close this valve a few times. If that doesn't stop the leak then you should replace the valve.
Dave M.
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message

That should have been an earlier step. The do go bad, they do leak. Once they start leaking they never stop.
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Edwin Pawlowski wrote:

I agree. I definitely would have done that before screwing around with the thermostats. If the water was hot enough to cause the TPR to open, it would be noticeable at the hot water faucets. 99% of the time, the cause of water coming from the valve is a problem with the valve itself, not an over pressure or temp condition.
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*Probably* it's a defective TPRV.
But original poster noted that the water "seemed hotter than normal the night before", from the description it does not sound like the TPRV is "leaking", it sounds like it's open - which means *some* sort of event opened it - from the post it does not sound like it was opened by the owner (for example, for testing).
All of which is enough to red flag it for me as a "Turn it off, and call the plumber" issue, at least if you want to be conservative and err on the side of safety.
For readers with a high speed connection, this is IMO sorta' interesting:
http://www.waterheaterblast.com/waterheaterblast.wmv
Something along these lines happens around 50 times a year in the US.
Michael Thomas Paragon Home inspection, LLC Chicago, IL mdtATparagoninspectsDOTcom eight47G5-5668
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