Tried but can't drain hot water heater

cam130navFebruary 29, 2008

Did my online research to no avail.

Problem: Two of my faucet's water pressure died.

History: Have had a lot of sediment come out of my upstairs tub (no aerator) for the past year.

I have been renting my home for around a year now (built in '03) and have always seen a large amount of sediment come out of this particular outlet (again no aerator). The other day my wife turned on said faucet and the downstairs kitchen faucet's water pressure died along with the upstairs sink. I did a little searching around and found out that the sediment (duh) might be the culprit. I cleaned out the aerators and the water pressure came back to life. Then I looked into how to drain the hot water heater. I followed the instructions - turn off pilot light (gas), shut off the water supply valve, turned on hot water to sink next to heater to prevent vacuum, hooked up hose to drain valve and opened up valve. Drained water for an hour an a half and the tank never emptied. I did a test and determined that the water was draining at approx 2 gal/min so it's draining fine (FYI-40 gal tank). After an hour and a half, I gave up and closed the drain valve. It only took seconds for the tank to fill up. The way I knew this was because the sink I had turned on hot only took seconds to start shooting out water when I opened the cold water supply. I checked to see if the sediment was still an issue by running the water without an aerator and then turning it off and then installing the aerator, then running the water for a bit. I then took the aerator off and the sediment was already built up quit a bit.

So why did the water heater never drain?


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When one drains a water heater in the conventional manner it can prove to be a very frustrating operation as you have well found out, however there are a couple things that you can do to make it a very simple task.

The generally accepted procedure is to first turn the burner off, whether you turn the gas off for a gas water heater or pull the service disconnect on an electric water heater, then turn the cold water supply off, open a hot water faucet to vent air in as the tank drains, attach a garden hose to the water heater drain valve and open the drain valve. While this method will sometimes work, in the real world quite often we find that we cannot get a good flow. Why?

1.In all probability the sediments in the tank are also built up in the drain valve nipple.
2. A garden hose has an extremely high coefficient of friction, especially at the beginning when the hose is still dry inside.
3.We are relying on purely static head pressure to propel the water and given that the water heater vessel is approximately 4' high the actual pressure is only 4'x .434psi per vertical foot or 1.76psi.

Try this. First connect the garden hose to the water heater drain port and run the hose to a drain or outdoors, then open the valve while the water pressure is still applied to the tank. This will force water through the hose at full line pressure to blow the sediment out of the drain valve nipple and pre-wet the hose, thus dramatically reducing the line friction in the hose. Once the water is flowing full force through the hose you can now turn the water heater cold water supply valve off and open a hot water faucet to allow air to vent into the tank while it drains.

An even better solution is to get a "Wayne Drill Pump" and a washing machine supply line. A Wayne drill pump is a simple little plastic centrifical pump that you attach to an ordinary electric drill motor. The pump has a standard hose thread on both the input and output ports. A washing machine supply line has a standard hose fitting on each end so I attach one end to the water heater drain valve, the opposite end to the input of the pump and a 3/4" garden hose to the output of the pump. I then attach a drill motor to the pump input shaft. I then open the water heater drain valve and allow the line pressure to start the flow. Once I have water flow through the hose I turn the water heater cold water supply off, open a hot water faucet and start the drill motor, locking it in the on position. The Drill pump will pump about 4 or 5gpm so I can generally empty a tank in about 10 minutes.

You can find the Wayne Drill Pump motors at any hardware store in the section where they have utility pumps. Typical selling price of the pump is $7.95.

    Bookmark   March 1, 2008 at 12:53AM
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Yeah, don't turn the water off.
You want to blast out the debris not drain it.

    Bookmark   March 1, 2008 at 1:21AM
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Not to sound like an a** but WHAT??? lazypup, if you read my post I don't have an issue with flow - "I did a test and determined that the water was draining at approx 2 gal/min so it's draining fine (FYI-40 gal tank)." Anyone have any useful input?

    Bookmark   March 1, 2008 at 9:03AM
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2gpm is not nearly enough velocity to expect the water to carry the sediments...but what the hell do i know,,,i am just a dumb plumber

    Bookmark   March 1, 2008 at 9:17AM
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You are the tenant in/on this property? Most landlords I know strongly discourage tenant "repairs" to property. Most such that I have seen appear to have been done by a blindfolded person using an axe.

    Bookmark   March 1, 2008 at 9:19AM
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In the original post you stated that you left the drain valve open for an hour and a half, which is 1.5 x 60minutes for a total of 90minutes. You further stated that you tested the flow rate and determined that it was flowing at 2gpm. From this you would have us believe that you drained 90min x 2gpm = 180gal of water. Now I ask you this, how is it possible to drain 180gal of water from a 40gal tank?

One could make the argument that there is additional water standing in the house hot water distribution lines but; a ½" line contains one gallon for each 98 linear feet and a ¾" line contains one gallon for every 43.4ft. Based upon these facts I doubt seriously if your house has sufficient water lines to contain 120gal of water in the distribution piping.

You then stated that when you finally re-opened the water heater cold water supply valve the tank refilled in a matter of seconds. This confirms two facts. 1. The coldwater valve does turn off and hold water and 2. The tank was only partially empty.

From this evidence I would submit that you may have had a 2gpm flow rate at the moment when you made your test, but that flow rate only lasted for a few minutes at best which is consistent with my previous experiences on this issue and further, it takes us back to what I previously suggested.

On the other hand, as was pointed out by Buss Driver, you further stated that you are renting this house. In most jurisdictions the Landlord & Tenant law strictly prohibits a tenant from performing any maintenance or alterations on a structure without the expressed written consent of the property owner.

    Bookmark   March 1, 2008 at 1:04PM
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This was a flow rate that allowed me to use the drain in my basement without getting water everywhere due to the drain cover. I had planned on partially filling the tank back up and then fully opening the drain valve to blast out the sediment by using a bucket versus the drain but never got the chance for obvious reasons.

I was in my basement the entire time it was draining and it stayed at that flow rate the entire time. I initially thought that it was standing water in the water distribution line but like you said seems a bit impossible.

My landlord asked if I would help out by doing this so not an issue.

BTW wasn't trying to infer that you were a "dumb plumber" but you have to admit your initial response had nothing to do with my post.

So no ideas as to why my water heater won't drain?

    Bookmark   March 1, 2008 at 4:27PM
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I find at times, I get frustrated when trying to correct a problem, my good sir Cam, you received very good info, and I"m not a plumber. After reading your intial post, I also thought there has to be supply water still entering the tank. Please read above again and you'll see lazypup gave you your answer.

    Bookmark   March 1, 2008 at 5:56PM
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ctbosox thank you for your reply but i am not frustrated. I am baffled! I understand that I have upset the folks here but that was not my intent. I am simply trying to get an answer to my question. And after reading lazypup's reply above again, no sir - he/she did not answer my question. WHY HASN'T MY HOT WATER HEATER DRAINED? I'm not trying to stump the dummy or piss folks off. I'm just your everyday American using the internet as a tool/venue. If you don't have an answer for me just say so. I'm not looking for a someone to blow pixie dust dust up my hoo hah!
I'm not trying to ge into a pissing match just looking for an answer. If ther isn't one - such is life.

So to recap I've followed the advice/instructions from the net, above and the owners manual of my hot water heater to drain it. I've had no luck as stated above and if anyone has any insight please reply. I think I'm doing something wrong but can't find anything to refute it.

    Bookmark   March 2, 2008 at 2:23AM
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I believe that there is still water entering the tank even after you shut off the valve. After letting it drain for an hour and a half, at 2gpm as you said, I would try using another shutoff valve feeding that line. If needed, shutoff the main coming into the house.

    Bookmark   March 2, 2008 at 7:44AM
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It is very easy to test the water heater shutoff valve. Just open any hot water faucet then close the water heater shutoff. If you continue to get full pressure flow from the faucet the water heater valve is not shutting off properly, in which case you would need to shut the water off at a zone valve or at the house main water shutoff valve.

    Bookmark   March 2, 2008 at 10:56AM
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ctbosox-I think there is too but can't figure out from where. There are only two ways in - the hot water line and the cold. I will try shutting off the water at the main line - any special considerations there.

lazypup-When I was trying to drain the tank I had the hot water faucet on in the bathroom in the basement. When the valve was off there was no water coming out. When I turned the valve back on the flow would obviously come back but with only 1-2 second delay - further proving that I never drained the tank. When I turn the valve back on, I hear rushing water so I think the valve is functioning properly. I tell you what this has really thrown me for a loop.
I guess I will try the shutoff valve to the house and will post back with result.

    Bookmark   March 2, 2008 at 11:28AM
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It won't hurt to double check the hot and cold shutoff valves, they both look the same to me, not sure but I think the tanks are marked inlet, outlet. shutting off the outlet, or hot, would give you same results your getting now.

    Bookmark   March 2, 2008 at 7:42PM
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my WH has 2 shut offs, one in for the cold supply and one out for the hot to the house. maybe yours does too and you cut off the wrong one? let the hot water run for a minute and feel the valve, if it is warm to teh thouch, then it is shutting off the hot to the house.

the shut off SHOULD be on the cold side, but who knows what some previous person did.

    Bookmark   March 3, 2008 at 11:31AM
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Could you have a faucet somewhere that is letting cold water run back through the hot water lines and into the tank? I know this can happen, I turned on the cold water in a faucet while my husband was dealing with hot water lines in the basement. Good thing he can yell real loud.

Also did you check the temp of the water you were draining? It should have stayed pretty hot, if it was getting cold then cold water was still entering the heater.

Seriously, if your flow rate was as you state, then water had to be entering the heater from somewhere -


    Bookmark   March 4, 2008 at 4:07PM
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Sounds like the same problem we had. The tank was hooked up backwards. The cold water side was actually feeding into the house with the "shut-off" valve in place, the hot side was receiving the outside water. When we shut what we thougt was the inlet valve and then opened the drain, water gushed out but the tank never drained - it was just maintaining the status quo. We had to shut off the water at the street/main in order to finally drain the tank.

    Bookmark   July 8, 2008 at 11:58PM
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Alternatively, your shut off valve may be stuck open or only partially closing. Best bet would be to go to the street/main to make sure the water is turned off.

    Bookmark   July 9, 2008 at 12:01AM
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Sounds like its air locked too. Clean your spigot with a piece of wire our blow it out with the cold water pressure. When you get the sediment out, engage the t&p valve (pop-off) This will break the air lock and drain the tank....

    Bookmark   July 9, 2008 at 5:19PM
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This is what worked for me. My water heater has a brass drain and I could not get a wire coat hanger up and through the bonnet. I removed the bonnet of the valve and then jammed a wire coat hanger though it and BANG! It busted through the blockage and white milky water came rushing out. I quickly replaced the bonnet and the water heater drained. GOOD LUCK!

    Bookmark   August 25, 2012 at 12:16PM
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