Water Heaters - I think my drain valve is clogged

Does anyone have suggestions for how to deal with a potentially clogged drain valve?

My dishwasher repair guy said that my clogged up dishwasher fill valve was likely caused by gunk in my hot water heater and that I needed to drain it.

So, I turned off the power (it's electric), turned off the water where it enters the house, turned on a hot water faucet at a sink, attached a hose to the drain valve, and opened the valve to drain the tank. The water started flowing nicely so I left it to drain.

When I came back later, the water had slowed to a trickle so I assumed that the tank was empty. I closed the valve and turned back on the water where it enters the house. (I left the water faucet open to let the air out.) When the air was mostly out, I was surprised that there was hot water coming out. So I let it run for a while... and hot water continued to come out. I was puzzled by this (I thought it would have been cold by then). But I continued restoring things to normal.

I disconnected the hose from the drain valve and a very slow trickle (just slightly more than a drip) of water came out... and it continued... and continued... even after a thorough drying. "Uh oh" I thought to myself.

So I reconnected the hose, turned off the main water, turned on the sink faucet and opened the drain valve again. I was expecting a nice flow like before but there was only a trickle. "Oh no" I thought again.

So I turned on the water to the house again and when the pressure built up, water was pouring out of the faucet. Feeling brave, I slowly turned off the faucet leaving the drain valve open. Still nothing more than a trickle came out of the hose.

I then closed the drain valve and disconnected the hose. The same slow trickle that I had seen before came out and I couldn't close the valve any more to stop it.

At this point, I think I have a clogged drain valve and whatever is clogging it appears to also prevent the valve from closing fully. I think this is a ball type valve because the handle only makes about a 1/4 turn to go from open to closed.

The heater is about 10 years old and although I've never drained it in the 3 years I've lived here, someone has because half of the plastic knob on the drain valve is broken off.

Does anyone have suggestions for what to do next?

One thought I had was to try to backwash the valve (assuming there is no backflow prevention on it). I was thinking I could get a nice, new clean piece of hose and put two female fittings on the ends. I'd connect one end of the hose to the drain valve and the other end to the male fitting on the utility sink nearby. Then instead of turning off the water to the house, I could turn off the water using the cutoff at the heater. I'd then open the drain valve, turn on the water at the utility sink and then open the overflow valve at the top of the heater. I am somewhat concerned about a backwash because it will likely contaminate the inside of the water heater with things like bacteria from the exterior of the drain valve or the hose. Is this a safe thing to do?

My thinking is that the backwash might be enough to unblock the drain valve and then I could do a proper "flush" instead of simply a "drain". (Gosh I wish I had come here before I started... I never thought about doing a "flush" until I saw it here.) However, if the debris clogging the drain valve is large enough, a flush would likely still result in another clogged drain valve and I'd be back to square one.

First a correction... the water heater is 20 years old and not 10.

Also, now that I've read further in this forum and seen how the T&P valve works, I tried using the T&P valve to be the vent. The result is essentially the same.

Turned off cold supply at water heater. Opened drain valve and then opened T&P valve. Nothing came out drain valve. Next opened the nearby hot water faucet. Nothing came out drain valve. Then opened T&P valve while hot water faucet and drain valve were open. Water drained out of the hot water faucet into the utility sink.

I've also tried repeatedly opening and closing the drain valve to no effect. I've also tried leaving the drain valve at 1/2 way open with nothing coming out either.

The heater is well beyond normal life expectancy. Anyway, I think your tank is full of mineral deposits. Probably 5 or more gallons worth. Sometimes you can get them to drain by leaving the supply valve open and the drain valve open. This may in some cases, clear a path through the debris in the tank. Once a good flow has been established, you can close the supply valve and open the t&p. If this doesn't work, you can proceed to plan two.

Plan 2:
Close the supply valve and open the drain valve. Get a stiff wire (a piece of 12 gauge copper wire works well) and run it into the valve. If done properly, the wire will clear a path through the debris. You may have to do this several times. I have successfully done this numerous times. If this fails go to plan 3.

Plan 3:
Shut off supply valve and unscrew (remove) the drain valve completely. Have a large bucket or other way of catching the water and junk that will flow. This method is ideal if your heater is located in an area where the resulting flow of water won't do any damage. One work of caution; some of those cheap plastic valves will break if not careful.

After you have completed the drain and flush, don't be surprised if your t&p drips. Also plan on replacing the drain valve as that will likely drip too. Your tank may start leaking as well. Not that draining causes leaks, but the sediment is likely stopping an existing leak. Sediment is a great leak stopper, as documented by the blocked drain valve.

Given the age of the tank, we went ahead and replaced it. The service guys disconnected it and hauled it outside (full of water) on a hand truck. To drain the tank, they knocked the drain valve off with a hammer. The valve was completely clogged with sediment.

We now have one of those Bradford White models that you aren't supposed to have to flush.

Thanks for letting us know how it turned out. We wish more people would.

Moving a full water heater is no easy task unless you have a helper or two. Let's see 50 gallons of water = 415 pounds, plus the heater will total about 550 pounds. If you have more muscle than time, that's the way to go.