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
2. Both heating elements continuity checked ok with one lead at a time
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,
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?
Disclaimer: I don't know if this is true but a plumber told me the
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.
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.
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).
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?
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
The hot fitting does not get a dip tube.
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.
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.
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.
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.
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.
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.
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