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AO Smith
Electric Water Heater

Model # ESTT40 Official AO Smith water heater

Here are the diagrams and repair parts for Official AO Smith ESTT40 water heater, as well as links to manuals and error code tables, if available.

There are a couple of ways to find the part or diagram you need:

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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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For DIY troubleshooting advice and repair guides, visit our repair help section.

Error Codes

Model diagram and schematic

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ALL PARTS
Showing 10 of 21 parts  |
Thermostat 183534-000
#12

Water heater diagram

Thermostat

Part #183534-000

Replaced by #9001954015

?
Manufacturer substitution
This part replaces 183534-000. Substitute parts can look different from the original.
BEST SELLER
$28.93 | 
17% OFF Phone Price : $34.93
Back Order
Element 042286-022
#6

Water heater diagram

Element

Part #042286-022

Replaced by #100108290

?
Manufacturer substitution
This part replaces 042286-022. Substitute parts can look different from the original.
$33.33
Back Order
Cover 183529-000
#19

Water heater diagram

Cover

Part #183529-000

Replaced by #9002276

?
Manufacturer substitution
This part replaces 183529-000. Substitute parts can look different from the original.
This item is not returnable
$17.69 | 
10% OFF Phone Price : $19.69
In Stock
Box Cover 184660-000
#14

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
Owner's Manual 183795-000
#NI

Water heater diagram

Owner's manual

Part #183795-000

$9.49
In Stock
Thermostat 183532-000
#20

Water heater diagram

Thermostat

Part #183532-000

Replaced by #9000507015

?
Manufacturer substitution
This part replaces 183532-000. Substitute parts can look different from the original.
$33.17 | 
15% OFF Phone Price : $39.17
In Stock
Bracket 184608-000
#11

Water heater diagram

Bracket

Part #184608-000

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

Drain Valve 042037-000
#4

Water heater diagram

Drain valve

Part #042037-000

Replaced by #100108778

?
Manufacturer substitution
This part replaces 042037-000. Substitute parts can look different from the original.
$18.57
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
Release Valve 076527-000
#9

Water heater diagram

Release valve

Part #076527-000

Replaced by #100108279

?
Manufacturer substitution
This part replaces 076527-000. Substitute parts can look different from the original.
$32.22
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 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 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 making the water too hot?

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

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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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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…

Read more
Repair difficulty
Time required
 30 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…

Read more
Repair difficulty
Time required
 30 minutes or less
How to replace a water heater temperature and pressure (T&P) relief valve

How to replace a water heater temperature and pressure (T&P) relief valve

Replace a broken temperature/pressure (T&P) relief valve on an electric water heater using these instructions.…

Read more
Repair difficulty
Time required
 15 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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Wiring schematic symbols explained video

Wiring schematic symbols explained video

Learn some of the most common symbols found in a wiring diagram and what they mean.…

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Using a wiring schematic to trace a current video

Using a wiring schematic to trace a current video

Find out what’s wrong with your appliance by following a circuit.…

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Easy DIY water heater repairs

Easy DIY water heater repairs

Read about some water heater repairs that you can easily do yourself.…

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