.Water heater problem?.

An elderly neighbor claims she has a water heater problem because she has a very limited amount of hot water available for use. I said I would check on it for her and here's what I did/didn't find:
1. It's an electric 40 gal. water heater with upper & lower 4500w elements. 2. Both heating elements continuity checked ok with one lead at a time disconnected. 3. The thermostats are 90-150 degrees and both set at 140. 4. With the hot water running, the lower thermostat & element kicked in within a few seconds. 5. With the water still running for a minute or two, the top element kicked in while the bottom one turned off. 6. After another minute or two the water went lukewarm. 7. During the reheat process the above sequence reversed - top first, then bottom.
Assuming that the process was correct and everything working, I thought of sediment in the tank. I hooked up a hose to the drain faucet and ran it into a bucket. The water was full force and clear.
I asked her if this was a new or old problem. She said the tank was about 10 years old and had worked fine until a month ago.
I'm stumped. Any other thoughts?
Bob
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Disclaimer: I don't know if this is true but a plumber told me the following:
Cold water enters a hot water heater from the top. The discharge is from the bottom because there is a tube inside the HW heater that makes it draw the water off of the bottom (even though the discharge is physically on the top). The tube is rusted out on the one you are working on so it is picking up the cold water that enters the tank. A jury rig that you can do is take a piece of copper (biggest that will fit) and stick it down inside the hot water discharge to near the bottom of the tank -- you can flare the top so it won't drop on in. It won't have to be really tight but it should make it draw off the bottom. The gentleman that told me this claimed that there were probably millions of HW heaters thrown away due to this.

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Sounds like your plumber friend doesn't know what he's talking about or you got it backwards.
Cold water is heavier than hot water. Cold water should enter the water heater and pass through the dip tube to near the bottom of the tank. The heated (hot) water is then extracted from the top of the tank. The dip tubes are usually plastic and may fail (there were many with cheap plastic dip tubes that failed in prior years). Replacing the dip tube with a copper tube will resolve the failed dip tube problem.
RB
Ken wrote:

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Ken,
You have it exactly backwards. Yes, the cold water enters the water heater at the top of the unit (on most water heaters) BUT it is the cold water that uses the dip tube to go to the bottom of the water heater. The hot water comes off the top of the water heater.
Think about it ...... ...... ...... heat rises. The hottest water will be at the top of the water heater so that is where you want to draw the hot water from. And you don't want to mix cold water with hot water you have heated with expensive electricity or gas so you want the cold water entering the water heater to go directly to the bottom (ergo, the dip tube).
Bob,
Check the water heater and make sure the connections are correct (i.e., cold water supply connected to the Cold connection and not vice versa). If the connections are backwards then you have what Ken described ... cold water entering the water heater at the top and warm water (not hot) being drawn off the bottom.
As an aside, I call them "water heaters", not "hot water heaters". Why would you want to heat hot water? If it is already hot then it doesn't need to be heated, does it?

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Bad dip tube is a problem. On some units.
On a correctly working WH, the dip tube goes on the pipe, under the cold fitting. Its purpose is to carry the cold water down to the bottom of the tank. Hot water exits at the top.
The hot fitting does not get a dip tube.
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The dip tube may have failed. However, at 10 years the water heater is a flood waiting to happen. I'd replace it.
RB
Bob S. wrote:

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"Bob S." wrote:

Not sure, but the sequence of heating doesn't sound correct. #5 doesn't sound right--the bottom shouldn't click off and the top go on and #7 doesn't sound right. The bottom should probably be on whenever the tank is cool enough that the top element goes on. I think you probably have a problem with the thermostats or a bad element is screwing up the action of the thermostats.
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I wondered about that too, but decided that since the cold water goes to the bottom of the tank, the bottom thermostat would activate first.
Since that is happening, I think much of the cold water is getting to the bottom of the tank, however the tube could very well be rusted/cracked and leaking cold water higher up the tank.
I also wondered about the thermostats. Is 140 degree typical? I would have thought 170-180 degrees would be normal but that is outside the range of the thermostat.
Bob
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Is there a mixing valve somewhere? Maybe on the shower control? Maybe you can check how much hot water is available in the bathroom where the shower is. Check the temp and number of gallons. You will have to chop into the tiled wall to replace the valve, so you want to be sure you're not chasing a red herring.
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"Bob S." wrote:

With normal use, most of the heating is done by the bottom element whether or not there is a tube to send the cold inlet to the bottom. A high flow through the heater would cause both elements to be on. Yep, 140 degrees is a recommended maximum for safety by various groups, some recommend a much lower temperature if there a small kids. Some dishwashers require/suggesst 140 degree water but everything else works ok at lower temperatures. 130-135 is a reasonable temperature for an electric heater.
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This one doesn't work that way - only one element at a time. Each element is 4500W, which corresponds to almost 20A. The heater circuit is only 30A total. It couldn't handle both elements on at the same time.

I figured it must be something like that. But on a side note, what about a gas heater? They seem to put out much hotter water.
Bob
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This is Turtle.
It just to me leaves the Dip Tube off or Bottom thermostat sticking or Top thermostat not turning the power over to the bottom thermostat at any given time. I don't know here for i would have to be there to try to decide who what or ever.
TURTLE
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