Description. Nautilus IW60 LP Gas Pilot & Direct Spark Ignition Tankless Water Heater (12-1/2" x 12-1/2" x 20-1/2") by Suburban. Enjoy endless hot water with Suburban's IW60 On Demand RV Water Heater. Say "good-bye" to waiting for water to reheat in a conventional tank. Showers and baths are best enjoyed slowly, so LIVE FREE from the restraints