The Model A is designed for operation under positive pressure (20 psi or greater). Both models employ the use of a rotating cylindrical drum with a number of threaded holes containing one of many types of straining media. The drum is supported on a rotating shaft fitted with bearings and is contained in a body having a vertical backwash slot opening adjacent to the drum surface.<a href="http://news.tencarva.comwp-content/uploads/2016/05/model-a-e1446680933975.jpg"><img src="http://news.tencarva.comwp-content/uploads/2016/05/model-a-e1446680933975.jpg" alt="model-a-e1446680933975" width="570" height="746" class="aligncenter size-full wp-image-999" /></a>