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CampWrench
AppliancesModerateAbout 45 min

RV water heater is not producing hot water

Taps run cold, or hot water runs out almost immediately.

Applies to: Tank-style RV water heaters including Suburban and Dometic/Atwood units, and tankless models where noted.

Quick answer

Check the winterizing bypass valve first. If it is still set to bypass, cold water flows straight past the tank and you will never get hot water no matter what the heater does. After that, the diagnosis splits by power source: on propane, work through supply, the burner and the thermal cut-off; on electric, check the element's high-limit reset button, which trips when the heater is switched on with an empty tank. Running the electric element dry destroys it in seconds and is the most common self-inflicted failure.

What usually causes it

  • Winterizing bypass still engaged

    Most common

    The bypass routes water around the tank for winterizing. Left engaged after de-winterizing, hot water is impossible regardless of what the heater does.

  • Electric element burnt out from dry firing

    Most common

    Switching on the electric element with an empty tank burns it out almost immediately. This happens most often right after winterizing or a tank drain.

  • High-limit reset tripped

    Common

    There is a manual reset button on the electric thermostat, behind the exterior access panel. It trips on overheat and stays tripped until pressed.

  • No propane or blocked burner

    Common

    Same story as the furnace and the fridge: supply problems, spider nests in the burner tube, and blocked exterior vents.

  • Thermal cut-off open

    Common

    A one-shot or resettable thermal cut-off on the gas side opens if exhaust gases spill. It usually points to a blocked flue rather than a faulty switch.

  • Sediment or a spent anode rod

    Common

    Sediment insulates the bottom of the tank and reduces effective capacity, so hot water runs out fast. A spent anode rod in a steel Suburban tank leads to tank corrosion.

Step-by-step diagnosis

Work in this order. Each step is cheaper or safer than the one after it, so stop as soon as the symptom clears.

  1. Check the bypass valves

    Find the bypass at the back of the water heater, usually behind an interior panel. Depending on the design there are one, two or three valves. Set them to normal operation, not bypass. If the RV has been stored or winterized recently, expect the answer to be here.

  2. Confirm the tank is full before applying heat

    Open a hot tap and let it run until water flows steadily. Air coming out means the tank is still filling. Never switch on the electric element until you have hot water flowing from a tap, or you will destroy the element.

    Dry firing the electric element ruins it within seconds. Always fill first.

  3. Press the high-limit reset

    Open the exterior access panel and find the reset button on the thermostat assembly. Press it firmly; you should feel a click if it had tripped. If it trips again on the next cycle, there is a genuine overheat or thermostat fault to investigate.

  4. Test the electric side

    With shore power on and the electric switch on, check for 120V at the element and measure the element's resistance with power disconnected. An open circuit means the element has burnt out and needs replacing.

    Disconnect shore power before touching element terminals.

  5. Work the propane side

    Confirm gas at a stove burner, then inspect the burner tube for spider webs and the exterior vent for nests. Blow the tube out with compressed air. Watch the burner light: you want a crisp blue flame, not yellow or lifting.

  6. Check the thermal cut-off and flue

    If the burner will not stay lit, check the thermal cut-off for continuity. Before replacing it, look for the blocked flue or spillage condition that made it open. Replacing the switch without fixing the cause simply moves the failure a week down the road.

  7. Flush the tank and inspect the anode

    Drain the tank and flush with a wand to remove sediment. On Suburban steel tanks, pull the anode rod and replace it once it is significantly consumed. Dometic and Atwood aluminum tanks do not use a sacrificial anode, so do not go looking for one.

  8. Set expectations for capacity

    A six gallon RV water heater is a small tank. Even in perfect condition it gives a short shower. If your complaint is that hot water runs out quickly rather than that there is none, the answer may be sediment, a low thermostat setting, or simply the tank size.

Safety notes

  • Never switch on the electric element with an empty tank.
  • Shut propane off at the tank before working on the burner.
  • Let the tank cool and relieve pressure before removing the anode rod or drain plug. Scalding water under pressure causes serious injury.

When to call a professional

Gas valve replacement, a leaking tank, and any repeated thermal cut-off trip after the flue has been cleared. A leaking steel tank is not repairable and needs replacement.

Frequently asked questions

Where is the reset button on an RV water heater?

Behind the exterior access panel, on the thermostat assembly attached to the tank. It is a small button that trips on overheat and must be pressed manually to restore operation.

Why did my water heater element fail right after winterizing?

Because it was switched on with an empty or partly drained tank. Dry firing burns the element out in seconds. Always fill the tank and confirm water flows from a hot tap before turning on the electric side.

Does my RV water heater have an anode rod?

Only if it has a steel tank, which typically means a Suburban unit. Dometic and Atwood tanks are aluminum and use no sacrificial anode. Fitting one where it does not belong causes problems rather than solving them.

How long should hot water last in an RV?

A six gallon tank supports roughly one short navy-style shower. If it drains far faster than that, flush the tank for sediment and check the thermostat setting before assuming a fault.

Also described as

  • rv water heater not working
  • suburban water heater no hot water
  • atwood water heater wont light
  • rv water heater reset button

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