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AO Smith
Electric Water Heater

Model # ESM20 Official AO Smith water heater

Here are the diagrams and repair parts for Official AO Smith ESM20 water heater, as well as links to manuals and error code tables, if available.

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  • In the search box below, enter all or part of the part number or the part’s name.

Not all parts are shown on the diagrams—those parts are labeled NI, for “not illustrated”.

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Error Codes

Model diagram and schematic

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Showing 10 of 21 parts  |
Owner's Manual 184639-000
#NI

Water heater diagram

Owner's manual

Part #184639-000

$9.99
In Stock
Ao Smith Panel 195888-000
#1

Water heater diagram

Ao smith panel

Part #195888-000

This item is not returnable
$7.49
In Stock
Bracket 184608-000
#11

Water heater diagram

Bracket

Part #184608-000

Replaced by #100108380

?
Manufacturer substitution
This part replaces 184608-000. Substitute parts can look different from the original.
$27.78
In Stock
Terminal Cover 182360-000
#10

Water heater diagram

Terminal cover

Part #182360-000

Replaced by #100109598

?
Manufacturer substitution
This part replaces 182360-000. Substitute parts can look different from the original.
$22.86
In Stock
Anode Rod 183523-016
#8

Water heater diagram

Anode rod

Part #183523-016

Replaced by #100109624

?
Manufacturer substitution
This part replaces 183523-016. Substitute parts can look different from the original.
$31.11
In Stock
Insulation 181639-003
#17

Water heater diagram

Insulation

Part #181639-003

Replaced by #9003971005

?
Manufacturer substitution
This part replaces 181639-003. Substitute parts can look different from the original.
$21.99
In Stock
Temperature Valve 043151-000
#9

Water heater diagram

Temperature valve

Part #043151-000

The manufacturer no longer makes this part, and there's no substitute part

Box Cover 184660-000
#19

Water heater diagram

Box cover

Part #184660-000

Replaced by #184660-000

?
Manufacturer substitution
This part replaces 184660-000. Substitute parts can look different from the original.
$17.99
In Stock
Insulation 183256-000
#16

Water heater diagram

Insulation

Part #183256-000

Replaced by #9003716005

?
Manufacturer substitution
This part replaces 183256-000. Substitute parts can look different from the original.
$23.49
In Stock
Drain Valve 042037-001
#3

Water heater diagram

Drain valve

Part #042037-001

Replaced by #100108443

?
Manufacturer substitution
This part replaces 042037-001. Substitute parts can look different from the original.
$26.67
In Stock

Most common symptoms to help you fix your water heaters

Choose a symptom to see related water heater repairs.

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Why isn't my water heater heating my water?

Main causes: lack of power, no gas supply, thermostat limit switch tripped, bad element, bad thermostat, gas valve failu…

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Why is there water in my water heater's drain pan?

Main causes: loose water pipe fittings, leaky drain valve, bad temperature-pressure relief valve, leaky heating element,…

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Why does my hot water smell like rotten eggs?

Main causes: water supply needs chlorine treatment, anode rod too reactive…

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Why isn't my water heater making enough hot water?

Main causes: broken heating element, thermostat failure, excessive tank sediment, tank size too small, burner valve asse…

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Why is my water heater's pressure relief valve dripping water?

Main causes: faulty pressure relief valve, water is overheating…

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Why isn't my water heater making the water hot enough?

Main causes: thermostats need adjustment, water heater capacity too low, bad heating element, thermostat failure, excess…

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Why is my water heater making the water too hot?

Main causes: thermostat temperature set too high, thermostats need adjustment, faulty thermostat, shorted heating elemen…

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Repair guides for electric water heaters

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How to replace a water heater element

How to replace a water heater element

If your water heater runs out of hot water quickly and one of the two heating elements has failed, replace the element f…

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Repair difficulty
Time required
 30 minutes or less
How to replace an electric water heater anode rod

How to replace an electric water heater anode rod

If your hot water begins to smell like rotten eggs, replace the anode rod with a zinc-aluminum anode rod following the i…

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Repair difficulty
Time required
 15 minutes or less
How to replace an electric water heater thermostat

How to replace an electric water heater thermostat

If the water temperature fluctuates or you don't get enough hot water, follow these instructions to replace your water h…

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Repair difficulty
Time required
 30 minutes or less

Effective articles & videos to help repair your water heaters

Use the advice and tips in these articles and videos to get the most out of your water heater.

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How to read a wiring schematic video

How to read a wiring schematic video

Learn how to decipher symbols so you can buy the right part for your problem.…

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Easy DIY water heater repairs

Easy DIY water heater repairs

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Water heater common questions

Water heater common questions

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