20 Gallon White Aluminum Water Heater Seaward Water Heaters offer a combination electric water heater/water heat exchanger which allows you to heat water at dockside with 110/120V AC power or while underway using engine heat. Polycoated aluminum exterior- will not corrode Marine grade aluminum heating tank Heat exchanger that won't rust or suffer leaky welds Ignition protected, UL Marine listed, high quality 1,500 watt/120V AC heating element that can operate dry without damage and is factory preset at 140 degrees fahrenheit, with a relief valve that goes off at 180 degrees fahrenheit 3/4" drain valve Hot and cold connections are 1/2" female NPT Heat exchanger ports are located on the front of the unit for easy access21"W x 27"H x 21"D20 gallonSh. Wt. 47 lbs.