I have been using a Walter’s two-valve float valve to fill a hot water holding tank that supplies all 7 pumps with water. I noticed recently the tank had drained completely starving the pumps of water. When the demand for hot water ceased, the tank filled back up. Upon observation of this happening, I notice the water was not flowing from the valve to the tank even when the float was in the down (fully open) position. I replaced the valve with my backup and it is now functioning properly. I tore apart the Walter’s valve and found the small inner rubber seal was completely destroyed. This is the second one I have gone through in a year and it happens without warning. Is this considered normal wear or do I have a flow/temperature problem? What is the recommended replacement time period for this diaphragm? Thanks!