Water heater question

[tmshort]

I have a "State select" electric water heater, was in the house when I moved in 5y ago, home built in 2005 so I'm guessing it's original.

Over the last week the limit switch on the top t-stat has been popping. I tested both t-stats and elements, and think I've fixed that issue.

I figured I'd drain / flush it while I was at it, and here's where it gets weird.

Power off at the main breaker. Hose on the drain to the sump pit. Supply off, and opened the drain. Water drained, not very hot. Drained it until just a trickle, then turned on the supply a few times figuring I'd flush it out a little. Water flowed from the hose until the supply was turned off.

Figuring I was done, I closed the drain, pulled off the hose, and opened the supply then went to turn on sinks and flush the air out.

There is still lots of hot water coming out ... not just lukewarm, but hot water!?!?!?

I can't think of how this is possible ... I drained it until nothing came out, then flushed a couple of times. Where the heck is the hot water coming from - the power was off the entire time, and is still off now.

Ideas??

 

[naturalgas]

There is a dip tube in water heater. As you draw hot water from the top cold replacement water is dropped in bottom of tank . Otherwise you would be drawing the cold water as it entered tank if no dip tube.To completely drain tank open relief valve to let air in or remove vacume valve.


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[brewchief]

It went into a vacuum, if no air can get into it from an open faucet it won't drain very much. Just opening the drain will often only let 5 gallons or so out.

 

[tmshort]

I had faucets open the entire time - no vacuum. It drained for an hour, until there was just a trickle.

Then I turned on the supply briefly in an attempt to flush it, water rushed out the hose again.

Perhaps it didn't drain completely ... that's the only thing I can think of. Unless there is so much sediment it has somehow partially divided the tank into two compartments ... ? Wouldn't make much sense. Aside from the limit switch tripping it's been working fine and making hot water.

 

[finn]

Imagine putting your thumb on a straw dipped into your soda and pulling the straw out.

The soda stays in the straw until you remove the thumb from the straw.

Next time you drain the heater, open the hot water faucet in the kitchen. (Shut off the cold water inlet to the water heater)

 

[KnurledNut]

Are you getting hot water at all other fixtures?
Is there another water heater?
Or a tankless electric heater under the sink?

 

[Richard Cranium]

was it the hot water that was already in the pipes.

 

[Angelfire]

When it was draining, was it draining pretty fast or seemed slow? If you have hard water, you may have buildup at the bottom that is limiting (or stopping outright) the speed at which it drains. We have pretty hard water and when I first opened up a the heater drain, nothing came out. I had to poke at it through the drain with a stiff wire before I could get any flow. Had to do this a few times as it would fill up with more debris as it drained.

 

[tmshort]

It's definitely not from another heater or under sink heater - like most of you on here, I've been through this house from top to bottom and know every nook and cranny, and have taken apart or repaired almost everything in it.

It drained pretty fast - about what I'd expect of gravity through a garden hose.

I don't have time to mess with it again this week, but when I get time again I'm going to drain it fully and pull the bottom element and peek around inside the tank with a light / inspection mirror.