Watts DET-5 2.1 G Potable Water Expansion Tank for 50-Gallon Water Heaters<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>Protects the water heater from thermal expansion^Absorbs the increased volume of water created when water is heated^For water heaters up to 50-Gallon^Contains a durable membrane to prevent contact of water with air in the tank^Pre-pressurized steel tank at 20 psi</li></ul></div><img src="http://ecx.images-amazon.com/images/I/41nvVdDRRoL.jpg" noproxy>