American Water Heaters
Gas Water Heater

Model #N40T121-403 Official American Water Heaters water heater

Here are the diagrams and repair parts for American Water Heaters N40T121-403 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:

  • Click a diagram to see the parts shown on that diagram.
  • 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”.

We encourage you to save the model to your profile, so it’s easy to access parts and manuals for your appliance whenever you log in.

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

Owner’s manualError Codes

Showing 10 of 14 parts

Water Heater Burner (replaces 3110024)#13A

Water heater Diagram

Water heater burner (replaces 3110024)

Part #186063-000
BEST SELLER
In Stock
$42.87 | 
10% OFF 
Phone Price: $47.87
Water Heater Dip Tube#6

Water heater Diagram

Water heater dip tube

Part #4710745
This item is not returnable
In Stock
$18.49 | 
10% OFF 
Phone Price: $20.49
Water Heater Electronic Control Board#10

Water heater Diagram

In Stock
$163.19 | 
6% OFF 
Phone Price: $173.19
Water Heater Pilot Assembly#12

Water heater Diagram

In Stock
$44.91 | 
10% OFF 
Phone Price: $49.91
Temperature and Pressure Valve#8

Water heater Diagram

Temperature and pressure valve

Part #6900828

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

Water Heater Anode Rod (replaces 4700375, 9000279, 900029, 9000379, 9000707, 9001543)#7

Water heater Diagram

Anode rod

Part #4700375
Replaced by #9001453
?
Manufacturer substitution
This part replaces 4700375. Substitute parts can look different from the original.
In Stock
$84.82 | 
6% OFF 
Phone Price: $89.82
Water Heater Manifold Door and Burner Assembly (replaces 6911154)#14A

Water heater Diagram

Burner assembly

Part #6911154
Replaced by #100093991
?
Manufacturer substitution
This part replaces 6911154. Substitute parts can look different from the original.
In Stock
$101.23
Water Heater Drain Valve#9

Water heater Diagram

Drain valve

Part #6900820
Replaced by #9000058015
?
Manufacturer substitution
This part replaces 6900820. Substitute parts can look different from the original.
This item is not returnable
In Stock
$17.66 | 
10% OFF 
Phone Price: $19.66
Manifold Door Gasket#16

Water heater Diagram

Manifold door gasket

Part #9006141015

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

Outer Door#11

Water heater Diagram

Outer door

Part #321345-000

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

Symptoms common to all water heaters

Choose a symptom to see related water heater repairs.

Main causes: thermostat temperature set too high, thermostats need adjustment, faulty thermostat, shorted heating element
Main causes: faulty pressure relief valve, water is overheating
Main causes: broken heating element, thermostat failure, excessive tank sediment, tank size too small, burner valve assembly failure
Main causes: lack of power, no gas supply, thermostat limit switch tripped, bad element, bad thermostat, gas valve failure, bad thermocouple
Main causes: water supply needs chlorine treatment, anode rod too reactive
Main causes: thermostats need adjustment, water heater capacity too low, bad heating element, thermostat failure, excessive tank sediment
Main causes: loose water pipe fittings, leaky drain valve, bad temperature-pressure relief valve, leaky heating element, cracked tank

Articles and videos common to all water heaters

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

October 24, 2022

Easy DIY appliance repairs that anyone can do

Easy DIY appliance repairs that anyone can do

Get advice on simple DIY fixes for appliances that you can safely do on your own.

April 10, 2020

Cleaning your appliances after a drinking water advisory

Cleaning your appliances after a drinking water advisory

Find out how to clean and flush household appliances once a boil water advisory is lifted.

August 1, 2015

Easy DIY water heater repairs

Easy DIY water heater repairs

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