The Float Valve with Wing nut is an excellent and simple way to keep sumps/tanks/reservoirs full of RO water. Recommended anytime when using an Automatic Shutoff Valve (ASO), or just as a top level control. Adjustable arm can be used in the vertical or horizontal position. NSF-approved PVC with stainless steel hardware. Replaceable seals are made of long-wearing, chemical-resistant Santoprene(R) rubber.