Suburban & Atwood/Dometic Water Heater Troubleshooting Guide

Suburban (steel tank)  Uses a replaceable magnesium or aluminum anode rod, 3/4” NPT, removed with a 1-1/16” socket. Check it every 3 months. Suburban recommends replacing it yearly, or sooner if more than 75% is consumed. Seal the threads with potable-water-rated thread tape
Atwood/Dometic (aluminum tank)  NO anode rod — uses a plastic drain plug instead. The aluminum-clad tank lining is self-protecting; there is nothing to periodically replace for corrosion control
Anode torque  No RV-specific factory torque spec is published; hand-tight plus a quarter turn with a wrench is standard field practice — over-torquing cracks the fitting boss on aluminum-adjacent housings

FIELD NOTE

If a customer asks for an “anode rod replacement” on an Atwood/Dometic unit, confirm the tank material first — selling or installing an anode on an aluminum tank heater is a wasted trip and a part that doesn’t fit correctly.

ECO location  Reset buttons live under the rubber cover on the water heater door/face, near the top — right-hand button typically resets the 12V DC/gas ECO (hi-limit) thermostat
1.  Confirm propane supply and that the tank isn’t empty or the valve isn’t bled down
2.  Check the exterior manual on/off switch — verify it’s actually in the ON position
3.  Check the 12V DC fuse feeding the water heater control board in the main panel
4.  Listen for the igniter clicking at the burner — no click with good 12V and gas points to the control board or igniter
5.  Click with no flame points to a gas supply, orifice, or electrode gap problem, not the board

Burn chamber clogged  Carbon flakes in the chamber block proper ignition — clean it out before replacing any electrical component
Electrode gap/corrosion  Clean electrodes with a soft brush; wide or corroded gaps cause intermittent DSI-FLT codes
Lockout after three tries  Suburban DSI runs a 15-second purge, then sparks, and tries three times before locking out. The red reset light stays on in lockout. Press the switch to reset after you fix the cause
No thermocouple on DSI  DSI units prove flame electronically through the electrode and board, so there is no thermocouple to test. Repeated lockouts usually come down to the electrode gap or wire, LP supply pressure, or low 12V DC or a poor ground at the board
Electric mode failure  Relies on the heating element, thermostat, and ECO — completely separate failure path from the gas/DSI side, so a gas-mode fault doesn’t mean electric mode is affected and vice versa

FIELD NOTE

Replacing the ignition board is often the last thing tried and the first thing quoted — it’s the most expensive part in the system. Work the burn chamber, electrode, LP pressure and 12V supply/ground first; boards fail less often than the internet suggests.

Suburban anode inspection  Every 3 months if usage is heavy; minimum annual check
Suburban anode replacement  At 75% consumption or annually, whichever comes first
Tank flush (both brands)  Every 3–6 months, more often in hard water areas or if the unit sits in storage
Atwood/Dometic aluminum tank  No anode service — just periodic drain-plug removal and flush