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Jason.W 07-10-2011 03:08 PM

Just flushed my hot water heater...
Hi all,

I just flushed my hot water heater and after turning back on the water, I notice the tank was making quite a bit of fuss while filling up - a lot of rushing water. So I checked the cold water inlet and it was wide open. So I left it there and my hot water heater filled up. I was hesitant though that things weren't just right and I opened up the emergency valve (close to the top) and a blast was muddy water came out (into a pot, thank God). Any ideas on what this could be from?

Also, I notice my cold water inlet valve doesn't seem to be shutting off. I'm afraid that my tank could overfill and explode? Yeah, maybe a little dramatic but I'm trying to err on caution. Could my tank overfill? Also, do I need to keep the water off until I can replace the valve on the cold water inlet?

Any thoughts? I would appreciate any guidance!!


Daniel Holzman 07-10-2011 04:22 PM

You said you flushed the hot water tank, then turned the water back on. By this, I assume you mean that you shut off the water supply to the hot water tank prior to flushing it. I am not sure this is necessary, perhaps one of the plumbing experts can comment, I believe a lot of people flush their tanks with the inlet valve left open.

Anyway, when you turned the water back on, "the tank made a fuss". I am not sure what that means. Since you had to refill the tank, you should anticipate the sound of water running into the tank and filling it. You also normally open a hot water faucet downstream to let the air out of the hot water line. My guess is when you opened the "emergency valve" (which I am guessing is the temperature and pressure valve (T&P) near the top of the tank, the air in the hot water line that had gotten in there when you drained the tank got expelled. That valve normally lets out hot water, and you need to be very careful about opening it, since you can easily burn yourself.

Now you seem to be concerned that the cold water inlet valve "doesn't seem to be shutting off". I am not certain I understand what you are saying. The cold water inlet valve is normally left in the open position, otherwise when you use hot water there would be no way to fill the tank back up. Are you saying that cold water seems to be constantly running into the tank through the cold water inlet valve? It should only run into the tank for as long as it takes to fill the tank, which will be a long time if you forget to open a hot water faucet downstream of the tank to let the air out. That may be why you are hearing water running. Try opening a faucet, if you get air out of it, that is the problem.

The T&P valve is meant to allow hot water to escape the tank in the event there is an overpressure or excessive temperature condition. That valve is not meant to be used to drain the tank, and it is not meant as an air vent.

AllanJ 07-10-2011 08:43 PM

I hope you shut off the gas or power before doing this flushing project. And have water gushing from a hot faucet upstairs biefore turning the heater back on.

A water heater run empty will be damaged by overheating. If electric, only a quarter of the tank emptied will leave the top heating element high and dry and it will burn out.

A small amount of rust can accumulate in the pressure relief valve but I would not know where a large amount of mud up there could come from.

The water heater is supposed to withstand the normal pressure of the water system and some more. There is no such thing as a water heater exploding from overfilling*. Normally the inlet valve is left open all the time; it does not open and shut like a toilet tank inlet valve.

* It can explode from overpressure caused by steam from overheating, or can spring a leak if rusted out.

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