Why doesn't my water heater drain?

I am going to replace my water heater. No problems, but it is 24 years old and I figure it is pretty full of debris.
I shut off the inlet, opened the drain, opened a few hot water taps to act as vents, and nothing happens. I opened the inlet and water comes out the drain. Shut the inlet and nothing comes out.
Shouldn't it just drain out? I suppose I could put compressed air on the inlet, but that wasn't necessary on other water heaters I have drained. Any suggestions?
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open the tpr valve DAVE
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A little bit drips out with the TPR open, but not much..
I will try compressed air next. Even if it does not push it out the drain, it should push most of it out the hot water pipes. Or so I would think...
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Toller wrote:>I am going to replace my water heater. No problems, but it is 24 years old

Try removing the supply fitting also. You don't suppose the drain is clogged with the sediment, do you? Tom Work at your leisure!
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Maybe it's full of debris?
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That's what I thought until I tried it with the inlet open. Then it ran fine.
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try pulling the bottom element out ;)

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toller wrote:

You're correct, it sure shouldn't work that way. Sounds like a classic case of crud at the bottom of the tank.
Try unscrewing the drain valve from the boss in the tank and probing around through the hole with a piece of coat hanger wire or similar to stir up and disloge what's there.
If it is electric, you could take out the lower element, but that'd make a big mess. But if you have a drain pan system, it wouldn't be too bad. With the lower element out you can stir up the crud on the bottom with a curved rod stuck through the element hole.
I presume you shut off those opened hot water taps when you opened the inlet valve and got water to come out the drain. If so, I suspect what's happening is that there's so much gunk down there that it takes full line pressure to push the water through.
HTH,
Jeff
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My name is Jeff Wisnia and I approved this message....

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Depending on your hot water pipe layout, it may just be air locked even with the faucets open. Try loosening ont of the top connections or opening the relief valve at the top of the heater to let air in. Don Young

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toller wrote:

If nothing else works, siphon it out.
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A professional trick I observed on a gas heater is to remove the gas valve/thermostat assembly (cut the pipes to the burner and the whole thing unscrews) and you'll get most of the water out. Tip the whole thing forward to get the last bit of water out.
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