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An RV tankless water heater heats water as it flows through the unit, providing hot water without waiting for a storage tank to recover. Consistent operation depends on adequate water flow, fuel and electrical power. “On demand” does not mean instant delivery or unlimited water while boondocking. Master Technicians Matt and Bart explain the basics, including temperature control, low-pressure troubleshooting and winterization.
When you open a hot-water faucet, water flows through the heater. Once the unit detects sufficient flow and its operating requirements are met, the burner heats water passing through the heat exchanger.
Closing the faucet stops the demand for heat.
Unlike a traditional tank-style heater, a tankless unit does not maintain a stored tank of hot water. This avoids repeatedly heating that stored volume between uses, although actual energy consumption depends on your equipment and habits.
Controls and requirements vary by model, so identify your installed heater before changing settings or following a maintenance procedure.
No. The heater needs time to begin heating, and water already sitting in the plumbing must pass through before hot water reaches the faucet.
The delay depends partly on the distance between the heater and the fixture. A bathroom or kitchen faucet farther from the heater may take longer to warm.
Allow the temperature to stabilize before making repeated adjustments. When practical, collect clean startup water in a container for another use rather than sending it directly into the gray tank.
A tankless heater does not have a storage tank that runs out and needs reheating. It can continue heating while its operating requirements are met, subject to any model-specific operating limits.
However, it still needs water, fuel and electrical power.
At a full-hookup campsite, your available water supply and wastewater connection may support longer use. Without hookups, freshwater capacity, gray-tank space, propane and battery charge remain limited.
Plan shower length around those resources. A tankless heater does not increase the capacity of your RV’s holding tanks.
Start with the temperature-control procedure in your heater’s manual.
If the unit has an adjustable controller, choose a comfortable setting rather than automatically selecting the highest temperature. Some systems work best with hot water alone at the faucet; others permit mixing with cold water as described in their instructions.
Check the water carefully before showering or washing, particularly for children or anyone sensitive to temperature changes.
Avoid treating faucet mixing and controller adjustment as interchangeable on every heater. The best method depends on the unit’s design.
Tankless heaters need a minimum flow to activate and continue operating. Reducing flow too far can cause the burner to shut off, even though water is still coming from the faucet.
Higher flow also requires the heater to warm more water at once. Depending on incoming water temperature and heater capacity, that can affect the delivered temperature.
Use a steady flow within the manufacturer’s requirements. Running another fixture while someone showers may change the flow and temperature.
Closing a showerhead’s pause valve can interrupt heating. When flow resumes, allow the temperature to stabilize again.
Low or fluctuating campground pressure can prevent reliable tankless operation.
Start with accessible checks:
Do not remove required pressure protection or increase pressure beyond your RV’s limits to make the heater operate.
If the campground supply remains inadequate, filling the freshwater tank and using the onboard pump may provide a more consistent source. Follow the RV’s instructions for switching water sources. Girard’s guidance identifies this as an option when low city-water pressure cannot be resolved.
Yes, when the installed heater’s requirements are met. Many RV tankless units use propane for heat and 12-volt power for controls, ignition and other operating components. The water pump also needs power when drawing from the freshwater tank.
Before relying on the heater without hookups, check:
Use shorter showers and avoid unnecessary temperature adjustments that send more water down the drain while you wait.
Yes. Its procedure may differ from a conventional storage-tank heater, but it still requires freeze protection.
Do not assume that having no storage tank means no water remains inside. Water trapped in the heat exchanger or plumbing can freeze and cause damage.
Bypass requirements are model-specific. Girard’s referenced guidance does not recommend winterization bypass kits for its tankless system, but that instruction should not be applied to every brand or installation.
Follow your RV and heater manuals for approved draining, compressed-air or RV-antifreeze procedures. Built-in freeze protection, if equipped, is not a substitute for storage winterization unless the manufacturer explicitly says otherwise.
Confirm the selected temperature, steady water flow, propane supply and electrical power. Note any error code and use the heater’s troubleshooting instructions.
If the problem persists, contact an authorized service technician. Burner adjustments, gas-pressure testing and internal electrical repairs require the appropriate training and equipment.
Special thanks to JonesIn2Go for helping create the video content.
Review your tankless water heater’s manual before your next trip to confirm its operating and winterization requirements.
Disclaimer: The information contained in this article is deemed to be true and accurate at the time of publication. However, due to the evolving nature of our products and services, there may be changes or updates that occur after this article was published. We encourage users to verify the contents and consult with their dealer or Keystone RV for the most current information. If you have any questions or require further clarification, please do not hesitate to contact your dealer or reach out to Keystone RV directly.