Slow-Draining Water Heater Tank

[skeezix]

Just a follow-up question:

When I drained my old heater tank the water just dribbled out. After an hour or so it ran out a bit faster. This was after I had opened the hot water tap that is next to the tank and after I jammed a coat hanger into the drain valve to punch through the accumulated sediment. I also had closed the water shutoff valve on the inlet side.

After I installed my new tank I had to partially drain it too. I turned on the hot water tap as before but when I opened the drain valve, little if any water flowed through the drain hose. Then I loosened the inlet union. I heard a rush of air and what to my surprise, the water flowed out the hose nicely.

I thought that opening a hot water tap would let the air in so the tank would drain quickly. Any ideas why this didn't work as expected???

 

[RS]

It's pretty common to have scale built up to the drain hole, it proves you need to drain it more often. Even then you should run a wire in the drain to loosen up the scale. About it not draining until you loosened the union, some valves have backflow preventers to prevent thermosiphon circulation. If you have a different faucet nearby try that next time. We drain our water heaters every fall but I have an air compressor hooked to the system so the water comes out with a lot of force.

 

[Mitchell-DIY-Guy]

No explanation but this has happened to me more than once, different tanks. No sediment. You’d think the tall tank would force the water out, but nooooo....

 

[Jeff Handy]

There is a difference between the processes of DRAINING or FLUSHING a water heater tank.

When I flush sediment from a tank, I don’t close any valves, or turn off the heater, I just open the drain valve, and full house water pressure stirs up the sediment and forces it out.
Sometimes the drain valve needs to be fully opened and closed several times, to help unclog the valve.

This does waste some water, but works better than turning off the incoming cold water and draining/flushing by opening the drain valve and some hot water faucets, in my experience.

The only time I just DRAIN a tank is when I am hauling it away, or lowering the level inside for servicing valves or nipples, changing elements, or soldering pipes on top, or emptying it if I have to lay it down to change an anode.

 

[frodo]

Some mixing valve type faucets will not work with only cold or hot water

if you had but the handle in the middle. It may have worked

Your best bet is the hot side of the washing machine box