US Water also offers a full line of commercial-grade 4.5 x 20 filter housings. 4.5 x 20 filter housings are generally for point-of-entry applications. This is the ideal filter you should put on a most average size houses. Systems are available in a number of configurations, including single, dual and triple applications. Inlet sizes available are 3/4 and 1. US Water 4-1/2 x 20 filter housings are equal to or better than Ametek, Pentek, Liquqtek, Hydronix, American Plumber, Culligan and any other 4-1/2 x 20 filter housing.