Atwood Marine 
Water Heaters for Boats
Review and Buying Tips

Atwood marine water heaters are among the favorite brands for water heating in the marine and boat industry. One of the main reasons for the Atwood popularity is its lightweight design, a design that provides greater flexibility for installation and servicing, longer tank life, and savings.

The great advantage of the Atwood marine water heater over other manufacturers is that Atwood is not using the metal tank for storing hot water but utilizes the corrosion-resistant aluminum alloy.

The aluminum-built tanks allow Atwood to use extreme weather conditions and eliminate the anode rods, which must be installed on most of the competitors' water heaters. Every model utilizes the casing, made again of the corrosion-resistant material and tough paint coating. Some models, such as EHM-6 and EHM-11, are even using the stainless steel casing, ensuring durability and higher resistance to seawater and corrosion.

Models review

Atwood marine water heater

Atwood produces several sizes and configurations of marine water heaters, where the 4-gallon model is the smallest one, while the 20-gallon is the largest unit. All 4, 6, 10, and 20-gal models are electric using one 1400 kW or 1500 kW heating element and operating on 120 or 220 VAC.

Almost all models are equipped with a heat exchanger to utilize the heat from the engine. What is standard for all the models is the recovery rate of 7.1 gallons per hour.

  • Model EHM-4
  • Model EHM-6
  • Model EHP-10
  • Model EHM-11
  • Model EH-20

All the models from above use one electric heating element and the heat exchanger connected to the RV's engine, while the models E-20 are electric-powered only.

The main component of all Atwood marine water heaters is the heat exchanger that is built tough, using the double-tube construction for efficiency and superior protection, so the engine coolant doesn't pollute fresh water.

Installation of the water heaters is easy and convenient due to its lightweight design, which goes from 20.5 lb. for 4-gallon models to 40 lb. for 20-gal models and small size (maximum is 16x16x29"). Most of the time, Atwood water heaters are installed on the floor using the brackets, and due to their small square size, the water heaters are ideal where minimal floor space is available.

All water heaters are equipped with temperature and pressure relief valves and a thermostat that is factory set and is not adjustable.

Since the water heaters use hot water coolant for heating fresh water, it is vital to ensure proper connections between the water heater and engine; otherwise, the leak could cause the loss of coolant, lack of hot water, and eventually engine failure. Keep in mind that if the engine coolant runs through the heat exchanger for too long, the heated water might be excessively hot. One of the Atwood marine water heaters, model EHP-10, is equipped with a thermostatically controlled high-efficiency heat exchanger, preventing water from being too hot.

When buying a new Atwood water heater, you will find information at the front of the unit, and it includes the model number, capacity in both gallons and liters, max. watts approved, volts, availability of the energy cut-off feature, and the power of the heating element. All the connections and fittings are conveniently located at the front of the water heater, allowing an easy installation and service approach.