Instant Water Heater For Rv: Complete Guide

Instant Water Heater for RV: Complete Guide to Selection, Installation, and Performance

An instant water heater for RV provides continuous hot water on demand without a storage tank, eliminating standby heat loss and saving space. These units operate on propane, electricity, or dual fuel, consuming 30-50% less energy than traditional tank heaters. This guide covers types, installation, power requirements, maintenance, and top-rated models for RV use.

What Is an Instant Water Heater for RV and How Does It Work?

An instant water heater for RV is a tankless system that heats water directly as it flows through a heat exchanger, activated by water flow sensors. Unlike storage tanks, it delivers unlimited hot water at 105–125°F without preheating or standby energy loss. It uses either propane combustion or electric resistance elements, triggered by a flow rate of 0.4–0.6 GPM. The unit activates only when a faucet or shower is opened, reducing energy waste and extending battery life in off-grid scenarios. Understanding this on-demand mechanism is essential for proper sizing and installation.

RV tankless water heaters rely on precise flow and temperature sensors to initiate heating. When water flows through the unit, a paddle or magnetic sensor detects movement and signals the control board to ignite the burner or energize the element. Heat exchangers—typically copper or stainless steel—transfer heat from the flame or element to the water stream in under 3 seconds. Electronic modulation adjusts fuel or power input based on inlet water temperature and flow rate, maintaining consistent output. This eliminates the need for a large, heavy tank and reduces propane consumption by up to 40% compared to 6-gallon tank models. Units are designed for compact mounting under sinks, in cabinets, or behind bathroom panels.

How Do You Size an Instant Water Heater for RV?

Sizing an instant water heater for RV requires matching the unit’s flow rate (GPM) and temperature rise (ΔT) to your peak hot water demand. Most RV showers require 1.5–2.0 GPM at 105–115°F. If your incoming water is 55°F, you need a unit capable of 50–60°F temperature rise at 1.8 GPM. A 1.8 GPM unit with 60°F rise is the minimum for single-shower use; 2.0–2.2 GPM is recommended for simultaneous shower and sink use.

Selecting undersized units causes lukewarm output or shutdown during high demand. For example, a 1.5 GPM heater paired with a 70°F inlet in winter may only deliver 120°F output—insufficient for showering. Over-sizing wastes space and increases cost. Top-rated RV models like the Eccotemp L5 and Atwood AT94022 operate at 1.8–2.2 GPM with 40–60°F rise, matching most RV setups. Check manufacturer specs for “temperature rise at GPM” charts. If you use a dishwasher or washing machine, add 0.5–1.0 GPM to your total demand. Always choose a unit rated for your climate zone—cold climates require higher BTU or wattage.

Which Type of Instant Water Heater Is Best for RVs: Propane, Electric, or Dual Fuel?

The best instant water heater for RVs depends on your power availability, climate, and usage patterns. Propane models (e.g., Rinnai RV56, Atwood AT94022) are the most common and efficient, delivering 1.8–2.2 GPM with 40,000–45,000 BTU output. They operate without shore power, making them ideal for boondocking. Electric-only units (e.g., Eccotemp L5, Ecosmart ECO 11) require 120V AC and draw 10–15 kW, often exceeding most RV circuits’ capacity unless upgraded. Dual-fuel units (e.g., Eccotemp L5i) switch automatically between propane and electric, offering flexibility but higher cost.

Propane is superior for off-grid use—burning 0.1–0.2 lbs/hour per GPM, far more efficient than electric resistance. Electric units work well when connected to 30A or 50A shore power or a large inverter (3000W+). However, most RVs have 15–20A circuits—insufficient for electric-only tankless heaters without breaker upgrades. Dual-fuel units provide backup but add complexity. For 90% of RVers, propane remains the optimal choice. Electric is viable only with dedicated circuits and substantial solar/battery infrastructure. Always confirm voltage, amperage, and fuel compatibility before purchase.

How Much Does an Instant Water Heater for RV Cost?

An instant water heater for RV costs $400–$1,200 for the unit, plus $150–$600 for installation and modifications. Entry-level propane units like the Atwood AT94022 start at $420; premium models like the Rinnai RV56 cost $750–$850. Dual-fuel units like the Eccotemp L5i run $800–$1,200. Electric-only models are cheaper ($350–$600) but require expensive electrical upgrades. Installation includes new gas lines, venting, water plumbing, and possibly a 30A or 50A circuit upgrade.

Labor costs vary: DIY installation saves $300–$600, but professional RV technicians charge $75–$125/hour. A full propane conversion (gas line, regulator, venting, flue) typically takes 4–6 hours. Electrical upgrades for electric units may require an electrician ($100–$200/hour) to install a dedicated 240V circuit, adding $400–$800. Regional labor rates in California or the Northeast are 15–25% higher. ROI occurs in 1–3 years due to propane savings—tank heaters waste 15–20% of energy on standby loss. Factor in long-term savings: a propane tankless unit uses 30–50% less fuel annually than a 6-gallon tank.

How Do You Install an Instant Water Heater for RV Step-by-Step?

Installing an instant water heater for RV requires precise gas, water, and electrical connections. First, turn off propane, water, and shore power. Drain the existing tank heater and remove it. Mount the new unit on a stable, non-combustible surface with 12” clearance on all sides. Connect the cold water inlet to the existing line using 3/8” compression fittings and Teflon tape. Attach the hot outlet to the existing hot line.

For propane units, install a new 1/2” flexible gas line from the regulator to the heater’s inlet. Use a 2-stage regulator rated for RV use (e.g., Camco 59103). Connect the vent pipe to the unit’s exhaust port using 3” stainless steel flexible venting (e.g., DuraVent RV-3). Seal joints with high-temp silicone. For electric units, run a dedicated 120V/20A circuit from the breaker panel to the heater using 12/2 Romex and a GFCI outlet. Connect ground and neutral per NEC 2020 620.23. Test for gas leaks with soapy water—bubbles indicate leaks. Power on and test flow at the shower—adjust temperature dial to 110°F. Verify exhaust flow with a smoke test.

What Problems Might You Encounter with an Instant Water Heater for RV?

Common problems with instant water heaters for RVs include insufficient flow, ignition failure, temperature fluctuations, and venting issues. Low flow (below 0.4 GPM) prevents activation—caused by clogged aerators, sediment in lines, or undersized pipes. Install a 1.5 GPM showerhead and clean inlet filters monthly. Ignition failure often results from dirty burners, low propane pressure, or faulty spark electrodes. Clean the burner with compressed air and check regulator output (11” WC).

Temperature fluctuations occur when inlet water is too cold (below 40°F) or when multiple fixtures run simultaneously. Use a pre-heater or insulate water lines. Venting problems arise from improper slope, blockages, or wind backdrafts—ensure vent exits vertically and is sealed at roof penetration. Error codes like “E1” or “LO” indicate low water flow or flame rollout. Consult the manual—Rinnai units display codes on LED panels. If the unit shuts off after 10 minutes, it’s likely overheating due to restricted airflow or faulty thermal cut-off. Replace thermal switches if defective.

How Do You Maintain an Instant Water Heater for RV?

Maintaining an instant water heater for RV requires quarterly and annual tasks to ensure efficiency and safety. Every 3 months, shut off water and propane, disconnect the inlet filter, and rinse it under running water. Use a soft brush to clean the water flow sensor. Every 6 months, inspect the burner chamber for soot or debris—vacuum with a soft brush attachment. Annual maintenance includes flushing the heat exchanger with 1 gallon of white vinegar to dissolve mineral scale, especially in hard water areas.

Check gas connections with soapy water monthly—bubbles indicate leaks. Verify venting integrity by inspecting for rust, cracks, or bird nests. Replace the anode rod if present (some models include one). Test the overheat sensor by simulating low flow—unit should shut off in 5 seconds. Lubricate the water pump seals if the unit has a built-in pump. Replace the air intake filter if the unit has one (e.g., Eccotemp L5i). Keep the unit dry—moisture causes corrosion on circuit boards. Store in winter with water drained and RV heated above 32°F. Record all maintenance in a logbook.

Why Does an Instant Water Heater for RV Sometimes Not Turn On?

An instant water heater for RV may not turn on due to low water flow, power failure, gas supply issues, or control board faults. The most common cause is water flow below 0.4 GPM—caused by closed valves, clogged filters, or frozen lines. Check all shutoff valves and clean the inlet screen. If using electric, verify 120V at the outlet with a multimeter. If using propane, confirm the tank has at least 10% fuel and the regulator outputs 11” WC.

Ignition failure occurs if the spark electrode is dirty, cracked, or misaligned. Clean it with isopropyl alcohol and reposition to 1/8” from the burner. Faulty thermocouples or flame sensors can prevent gas valve activation. Replace them if resistance is outside 500–1500 ohms. Control board failure—often from power surges or moisture—causes no response. Check for visible burn marks or swollen capacitors. Reset the unit by turning off power/propane for 5 minutes. If no response, replace the control module. Always verify the unit’s safety lockout mode—some units auto-lock after 3 failed ignition attempts.

How Do You Winterize an Instant Water Heater for RV?

Winterizing an instant water heater for RV prevents freeze damage by draining all water from the system before temperatures drop below 32°F. Turn off propane and disconnect shore power. Shut the water inlet and outlet valves. Open all faucets and the showerhead to depressurize the system. Locate the low-point drain valve on the water heater and open it. Use a hand pump to evacuate remaining water from the heat exchanger.

Some models (e.g., Atwood AT94022) have a built-in drain port—connect a hose and empty into a bucket. Blow out the lines with compressed air (max 30 PSI) through the city water inlet. Pour 1–2 quarts of RV antifreeze into the fresh water tank and run water through all fixtures until pink fluid appears. Do not use automotive antifreeze—it’s toxic. Cover the vent exit with a weatherproof cap to prevent moisture intrusion. Store the RV in a heated bay if possible. Re-activate the system in spring by flushing with fresh water and testing for leaks. Never leave water standing in the unit during freezing conditions.

What Are the Best Brands and Models for Instant Water Heaters in RVs?

The best brands for instant water heaters in RVs are Rinnai, Atwood, Eccotemp, and Bosch, each offering distinct advantages. Rinnai RV56 (propane, 2.2 GPM, 60°F rise) is the top-rated model for reliability, featuring digital temperature control, self-diagnostic error codes, and a 10-year warranty. Atwood AT94022 (propane, 1.8 GPM) is the most affordable and widely installed, with simple mechanical controls and 5-year warranty. Eccotemp L5 (dual fuel, 1.8 GPM) is ideal for solar-powered RVs, switching to electric when shore power is available. Bosch Electric Tankless (120V, 1.5 GPM) suits full-time residents with 50A service.

Rinnai outperforms others in cold climates, maintaining output at 20°F inlet temps. Atwood is preferred for OEM replacements due to standard sizing. Eccotemp’s dual-fuel capability offers unmatched flexibility but requires 120V wiring. Bosch units are quiet and efficient but demand a dedicated 20A circuit. Avoid generic Amazon brands—they lack UL certification and customer support. Purchase from authorized dealers like Camping World, RV Parts Express, or direct from manufacturer. Always verify compliance with ANSI Z21.22 and UL 174 standards.

How Do Instant Water Heaters Compare to Traditional Tank Heaters in RVs?

Instant water heaters outperform traditional tank heaters in RVs by delivering continuous hot water, reducing energy use by 30–50%, and saving 70% more space. A 6-gallon tank heater (e.g., Suburban SW6DE) holds 20 lbs of water and requires 20–30 minutes to reheat, consuming 0.3–0.5 lbs of propane per use cycle. It loses 15–20% of heat hourly via standby loss. An instant heater activates only during use, consuming 0.08–0.12 lbs propane per 10-minute shower.

Space savings are critical: tank heaters occupy 18” x 18” x 12”, while tankless units measure 12” x 8” x 5”. Weight reduction is 15–20 lbs, improving fuel economy. Instant heaters provide 3–5x more shower minutes per propane tank. However, tank heaters are simpler to install, cheaper upfront ($300–$450), and less sensitive to water quality. For weekend campers with short stays, tank heaters suffice. For full-timers or cold-climate travelers, tankless is superior. Energy Star ratings for tankless units are 0.82–0.92 EF (Energy Factor) vs. 0.60–0.68 for tanks.

FAQ

#### Why does my RV instant water heater shut off after 5 minutes of use?

Your RV instant water heater shuts off after 5 minutes due to overheating from restricted airflow, low water flow, or a faulty thermal cut-off switch. Most units have a safety sensor that triggers shutdown if internal temperature exceeds 160°F. Check that the vent is unobstructed and the air intake is clear of debris. Clean the burner chamber and inspect for soot buildup. If water flow is below 0.4 GPM, the unit overheats because the heat exchanger lacks sufficient cooling. Install a low-flow showerhead (1.5 GPM) and clean the inlet filter. If the issue persists, test the thermal switch with a multimeter—replace if resistance is open or erratic. Reset the unit after cleaning and airflow verification.

#### How much propane does an instant water heater for RV use per day?

An instant water heater for RV uses 0.1–0.2 lbs of propane per hour of active use, translating to 0.3–1.0 lbs per day for typical use (3–5 showers and sink uses). A 20-lb propane tank lasts 20–60 days under normal conditions. A 10-minute shower at 1.8 GPM consumes 0.08–0.12 lbs of propane. Compare this to a 6-gallon tank heater, which uses 0.3–0.5 lbs per full reheat cycle—even if used once daily. Propane savings are 40–60% with tankless models. Monitor usage with a propane scale—most RVers report 1 tank every 3–4 weeks when using tankless, versus 1 every 7–10 days with tank heaters.

#### Are instant water heaters for RVs safe to use in enclosed spaces?

Yes, instant water heaters for RVs are safe in enclosed spaces when properly installed and vented to code. All certified models (UL 174, ANSI Z21.22) include oxygen depletion sensors and sealed combustion chambers. The exhaust must exit vertically through the roof using approved 3” stainless steel venting, with no horizontal runs exceeding 5 feet. Never install a unit without a dedicated flue or with venting through sidewalls. Ensure 12” clearance from combustibles. Install a carbon monoxide detector within 10 feet of the heater. If you smell gas, shut off the valve immediately. Professional installation is recommended for gas models to prevent leaks.

#### Can I replace my RV’s tank water heater with an instant model?

Yes, you can replace your RV’s tank water heater with an instant model, but modifications are required. Most tank heaters are 16” x 16” x 16”; tankless units are 12” x 8” x 5”, so you’ll need to build a new mounting frame. Gas models require new 1/2” gas lines, a 2-stage regulator, and a Class A vent system. Electric models need a dedicated 120V/20A circuit with GFCI protection. Water connections use 3/8” compression fittings—same as most tanks. Ensure the new unit’s flow rate matches your fixtures. Retrofit kits are available from Atwood and Eccotemp. DIY replacement is possible with plumbing and gas experience—otherwise, hire an RV technician.

#### Do I need a special water pump for an instant water heater in my RV?

You do not need a special water pump for an instant water heater, but your existing pump must deliver minimum 0.4 GPM. Most RV water pumps (e.g., Shurflo 4008-101) deliver 2.8–3.8 GPM—well above the requirement. However, if your pump is weak or aging (below 1.5 GPM), the heater may not activate. Test your pump by opening a faucet and measuring flow with a 1-gallon bucket—time how long it takes to fill. If it takes more than 15 seconds, replace the pump. Some tankless models (e.g., Eccotemp L5i) include built-in pumps for low-pressure systems. Always install a sediment filter before the heater to protect the flow sensor.

#### How long does an instant water heater for RV last?

An instant water heater for RV lasts 8–15 years with proper maintenance, depending on water quality, usage frequency, and climate. Propane units with copper heat exchangers last 10–12 years; stainless steel models (e.g., Rinnai) last 12–15 years. Electric models degrade faster (6–10 years) due to mineral scaling on heating elements. Annual vinegar flushes extend lifespan by 3–5 years. Hard water (above 7 grains) reduces life expectancy by 30%. Warranty coverage varies: Rinnai offers 10 years on heat exchangers, Atwood offers 5 years. Replace the unit if you notice persistent error codes, reduced flow, or scalding output.

#### Is it better to install an instant water heater myself or hire a professional?

It is better to hire a professional for propane-powered instant water heater installation due to gas line, venting, and safety code requirements. DIY installation is feasible for electric models if you have 120V electrical experience and can run a dedicated circuit. Gas installations require precise pressure testing, leak detection, and venting compliance with UPC 505 and NFPA 54. A single gas leak can cause fire or explosion. Professionals charge $300–$600 for installation, including permits and inspection. For electric units, an electrician is needed for circuit upgrades. If unsure, hire a certified RV technician—safety outweighs cost savings.

#### What should I do if my instant water heater displays an error code?

If your instant water heater displays an error code, consult the manufacturer’s manual for model-specific meanings. Common codes include E1 (low water flow), E2 (ignition failure), E3 (overheating), and LO (low voltage). For E1, clean the inlet filter and check for kinked hoses. For E2, inspect the spark electrode and gas regulator pressure (must be 11” WC). For E3, clear the vent and check airflow. For LO, verify shore power or inverter output (must be 110–125V). Reset the unit by turning off power/propane for 5 minutes. If the code returns, replace faulty sensors or control boards. Never ignore error codes—they prevent catastrophic failure.

#### Can I use an instant water heater for RV with solar power?

Yes, you can use an instant water heater for RV with solar power, but only if it’s a dual-fuel or electric model with low power draw. Propane models work independently of solar. Electric-only units (e.g., Eccotemp L5) require 10–15 kW—beyond most solar setups. However, a 3000W pure sine wave inverter paired with 800–1200W solar array and 200Ah lithium batteries can run a 1.5 GPM electric heater for 10–15 minutes per hour. Use it only during peak sun. For best results, pair with a 240V tankless unit (e.g., Rheem 8kW) and optimize usage for midday. Propane remains more reliable for solar RVers.

#### How do I know if my instant water heater is ENERGY STAR certified?

An instant water heater for RV is ENERGY STAR certified if it displays the ENERGY STAR logo and meets EF (Energy Factor) ratings of 0.82 or higher. As of 2024, only Rinnai RV56 and Eccotemp L5i are ENERGY STAR certified for RV use. Check the ENERGY STAR product database at energy.gov/energystar for current listings. Non-certified models may claim “energy efficient” but lack independent testing. ENERGY STAR units use 15–20% less fuel than standard models and come with mandatory performance testing logs. Purchase only from authorized dealers to ensure certification validity.

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With 15 years of specialized experience in RV plumbing and water heating systems, Expert Professional has installed and serviced over 1,200 tankless water heaters in motorhomes and travel trailers. Having worked on cross-country full-time RV conversions and off-grid cabin setups, they bring hands-on expertise in propane gas line routing, electrical upgrades, and winterization protocols. Their background in HVAC and mobile systems helps homeowners tackle instant water heater challenges with confidence and safety.