I am a computer guy, not a handy-man, so forgive the stupidity of my
I have a Rheem 40 gallon water heater.
240 volts, 4500 wattage, model number 81V40D C ...
My dad, a water heater inspector for TVA, tells me the top element is
probably bad (We have some hot water, but runs out pretty fast now... i
trust his judgement since he has done it for over 25 years).
So I go to home depot to grab a new element, and I am seeing screw in,
twist in, walk in, fly in, run in, etc... :^)
can someone just tell me what to get and where to get it? Pretend I am
your stupid son and feel sorry for me and hook me up. My dad just says
"Buy a new hot water heater, they dont cost much" but I dont have time
for all that, guests arrive in about 10 days.... I know all i will have
to do is turn the breaker off, let the water cool, drain the tank, and
pull (or twist, or unscrew) the element out and slap a new one in
However, I dont have an ohm meter.... i mean, does the average guy have
one of these lying around? Ive replaced light fixtures and ceiling
fans, but the more i read the more people seem to freak out about the
water heater still haveing power in it even after turning it off at the
breaker... what gives?
anyway, thanks in advance!
Your dad may be right about just replacing the whole thing. You need to open
the upper access panel, remove the insulation and check the two terminals on
the upper element with a volt meter to see that you indeed have 240 volts
across them, if not, you may need an upper thermostat, if you do, check to
see what holds the element into the tank, and remove it. Mind you, if its a
screw in, you need a pretty big socket wrench to get it out. With it
removed, bring it to a plumbing supply and get a replacement and gasket, and
Don't have time for all that? You might be a little mistaken about how hard
it is the install one. I myself had to install a new gas water heater and
that is by far more complicated - it took about 30 minutes once it was
on-site for me to do. Of course my buddy helped out, just because they are
empty doesn't mean they are light!
How old is your water heater - that would greatly help us provide more
get any hot water. That is the one that comes on first. That is the
"quick recovery element" to put some hot water in the top of the tank
right now. When the top thermostat is made it switches to the bottom
and heats up the rest of the tank. If top one is bad it won't make any
hot water to make the stat and flip to the bottom so you are stuck.
A quick look under the bottom cover will tell you what kind of element
it is. If it has 4 bolts around the wiring terminals (3" or so
pattern) it is bolt in. A screw in only has a big hex nut type end.
BE SURE TO TRIP THE BREAKER BEFORE YOU POKE AROUND IN THERE!
Also be sure water is running free out of a hot water faucet before
you turn it back on after replacing the element Let it run a minute or
more to be sure there isn't an air pocket in the top or you WILL have
a bad top element.
Disagree again. Bottom one comes on first because that's where the
coldest stored water is. Also, the cold water in dip tube goes to the
bottom of the tank.
Disagree. When the top thermostat says turn on, it shuts the bottom one,
which should already be on, off. When the top is up to temp, the bottom
will go back on to bring the lower half of the tank up to temp.
Hmmm. Now I am rethinking this (after posting of course!). If the top
one was bad the thermostat would apply the power to it but it never goes
on. It would always be on never switching to the lower. I eat my original
Assumptions: Two elements, an upper and a lower. Temp setting the same on
both. Same thermostats providing the same upper and lower limit swing.
State: No water being drawn. Tank just sitting.
Colder (denser) water will be at the bottom of the tank. Heat rises. When
the temp at the bottom of the tank goes below the lower thermostat limit,
the lower element goes on until the water at the bottom is up to temp.
Element goes off. Top element never comes on.
State: Hot water being drawn lightly/intermittently.
Hot water being drawn from the top of the tank. Cold water being fed into
bottom of tank from inlet/dip tube. When the temp at the bottom of the
tank goes below the lower thermostat limit, the lower element goes on.
Providing the demand is not high, the upper element will not go on
because the low limit of the upper thermostat is not reached. Bottom
water reaches temp and thermostat shuts off. Top element never comes on.
State: Hot water being drawn heavily like shower or hot water wash.
Hot water being drawn from top of tank. Cold water inlet being fed to
bottom of tank via dip tube. Bottom element goes on. Demand is faster
than lower element can heat. Lower limit of upper thermostat is reached.
Upper element goes on. Lower element turns off. Upper element stays on
until the water in upper tank is up to temp. Upper element goes off.
Lower element goes back on until water at bottom of tank is up to temp.
I'm no plumber, heating guy or any of that. This is just my
If they are both the same age I would think the bottom one would go first.
It goes on first since cooler water will be at the bottom of the tank. See
diagram at http://home.howstuffworks.com/water-heater1.htm
My guess is one of two things. The bottom one is bad. If the top was bad,
that would try to turn on. When the top turns on the bottom shuts off.
Since the top is bad, water never heats and bottom never comes on.
No experience personally but I have heard of cases of a cracked/broken dip
tube inside the tank near the top. Cold water gets fed to the top of the
tank instead of the bottom.
Turn the breaker off then run a hot water tap until it is cold. Much faster
than waiting for it to cool.
Open hot water faucets and the pressure relief valve too.
If you have high lime/calcium in your water, I had a personal situation
where it built up around the lower element to the point the bad element
would not come out of the hole. When i finally got it out by breaking it,
the bottom of the tank was full of white crud. Nightmare.
Go get a cheap AC tester. You'll find other uses for it. FYI, don't get a
cheap analog/digital multimeter. It will probably be low impedance and give
you inaccurate readings in some cases.
I don't know what the symptoms are when the top element is bad, but
when I had the same symptoms as you, it was the bottom element. I
figured that out by using a volt-ohmmeter. Sometimes called a
multi-meter. They have them at Radio-Shack for under 20 dollars. If I
recall what they sell, I wouldn't get the cheapest little one with a
needle movement, but the next one up, which happens to be digital.
(Nothing wrong with an "analog" meter, one with a needle, but the
cheap one they sell is just too small. Digital meters do have
advantages, though, such as usually auto-polarity. Even when
measuring a DC voltage, like testing a battery, you don't have to have
the red on positive and the black on negative. It will just show a
negative sign if you connect it backwards. Some digital meters have
auto-ranging, but one can live without that....)
As someone said, if you take the cover panel off (to check which one
you need, and if you need the heater or the thermostat -- neither are
hard to replace) you'll see if you want screw in or bolt-in.
OTOH, if you went to a Rheem dealer, he would know. OT3H, who are you
going to believe, the dealer or your own eyes? I doubt the dealer
would make a mistake, but if you see 4 screws arranged in a square
around the element, it's bolt in. If there are no screws, it's screw
in. That is, the whole element screws in.
The easiest way to check the element to see if it is bad is to turn
off the breaker for the water heater, use the scale of the voltmeter
that is higher than 220 volts AC to measure the voltage between the
two screw terminals on the element (always measure voltage before
measuring resistance, to see if it is safe for the meter to measure
When you see that there is no voltage, use the continuity setting,
the buzzer, to see if the heating element is continuous from one screw
to the next. Aha, but since the water is fairly cold by now, both
thermostats may be on, so if one heating element is bad, it is still
in parallel with the other heating element maybe, probably, so you
need to disconnect one wire from the heating element, and then measure
the continuity of the heating element. It will show as bad now if it
is bad. You can also use any of the ohm scales, especially the lowest
one, to measure ohms. If the heater is good, it will show zero or
close to it. If the heater is bad, it will not change from when the
probes are not touching anything. The reading will be blank, or
dashes, or something like that. You can verify the meter is working
by connecting its two probes right together and it should say zero or
very close to zero.
If it is not the heating element, again (remember that the power is
still off. At least you were supposed to have turned it off) then put
the two probes on the two screw connectors of the thermostat, which is
a square thing with a dial on it right next to the element. Same
thing as above. Since the water is cold now, at least cold enough
that the heater should be heating, the thermostat should be closed.
Because I didn't know I could get heating elements at a hardware
store, I got up early and went to the AOSmith dealer in town (I had an
AOSmith heater iirc) and he sold me what I needed, and because I talk
a lot (as you can see here) I said something like this, and he said
there was no need to drain the tank, which is time-consuming and
wastes water and hot water. IIRC, he had me turn off the main water
supply to the house, hot and cold, then open the lowest HOT water
faucet in the house, the basement sink. Some water will come out, but
after a few minutes, no more will. Because if new water can't get in
the other end, water can't come out this end. Air pressure, growing
Then go to the water heater, have the new element ready, the wires
disconnected from the old element, remove the element and as quickly
as possible put the new element in and start screwing it in or bolting
That's what I did and I didn't lose more than 2 or 3 tablespoons to a
quarter cup of water. Not positive because some went into the
insulation inside the water heater, but it was very little. Because
of turning off the water to the house and opening the hot water
faucet, there was no pressure so the water idn't come out with force
and there was no problem putting the new element in, which there would
have been I guess if the water pressure were on.
You could use the USB port. Just go into DOS, or Command I guess it
is called, and type "voltmeter". That will measure the voltage at the
first USB port. Wait a second.... No, that was just a dream I had
once. You need a separate meter.
It's the air conditioning where this happens because there are two
breakers powering the AC, but you really shouldn't be doing anything
electrical more than changing a lightbulb wihtout a meter. Maybe you
turn off the breaker and a helpful family member turns it back on.
Maybe you develop geriatric dyslexia and turn off the wrong breaker.
You need someway to see the electricty, and the meter is the best way.
Never measure ohms until after you have measured voltage. There
should be no voltage when you are measuring ohms.
loved the DOS joke... lol!
I bought two elements today, called rheem customer support and they
told me what to get, i also bought the tool used to screw them in
(since they are screw in). Figured id replace bouth.
I was thinking "the heater is 12 years old, ill just buy a new one" but
the installed price was like over $700, so I fugured I would try this
Yeah, my dad told me about the "quick draw" mehtod, but all the same i
think I will drain it, in case there are any sediments...
if you guys dont hear from me by this weekend, it went well... if it
was a disaster, ill prob be back.
PS... yes, tennessee valley authority. Honestly, he has worked there my
whole life and retired recently,... and still, to this day, I cant tell
anyone what my dad does or did... i always jut say "He works for TVA"
that either stumps them or they nod in understanding... either way they
12 years ain't that old so replacing the element was probably a good call.
I would definitely drain it before working on it, in doing so you might also
get rid of whatever it was that caused the problem - like all that rust and
Watch the drain, sometimes they don't want to shut off after you open them,
might just try to flush the drain with water if it doesn't want to close all
the way - sometimes rust and or minerals get caught in the valve.
Saw a guy change a pressure relief valve doing "quick draw" as you call
it. Neat. With risk of soaking stuff due to lack of personal experience,
I drain. And like said, suppose to periodically drain from valve anyway
to extend lower element life.
Called rheem, asked them exactly what to buy at home depot, installed
it in only a few hours (would have been less than an hour but my
neighbor took his time bringing my screwdriver back that i lent him
I did drain, and, as everyone suspected, it was the bottom element (but
i replaced them both).
OOops. If the heater is good, it will show a low value, but not zero.
With analog meters, where the ohmmeter part has to be "zeroed", and
where different scales zero maybe a bit differently, I got used to
thinking, in places where the actual value wasn't critical, where I
was using the meter to decide if there was continuity or not, of
anything close to zero as zero.
I'd get your dad to help plumb a natural gas line and put in to new
water heater. Electric water heaters are inefficient. Ofcourse, you
could also forget the element, and put a solar panel on the roof to put
hot water in there.
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