The Purely H2O plastic float valves are great for automatic level control applications. Our valves are completely corrosion resistant and perfect for salt water and RO water where metal valves cant be used. Our plastic float valve is small and easy to install with built in 1/2 inch threaded bulkhead input. Plastic parts keep from freezing up due to rust or corrosion. There is a small stainless steel cotter pin at the swivel point above the waterline. You will love this valve or your money back! No questions!A float valve is used to control the level of liquid in a storage container and prevent overflow and flooding. It is very common for people to try to manually fill a container and forget about it just long enough for the container to overflow and flood the area they are working in. Installing a float valve in the container allows you to leave and go about your daily activities without having to worry about coming home to a swimming pool in your living room.Reverse Osmosis is a very slow process of water filtration and water changes can be extremely time consuming. Performing a simple 15 gallon water change can be a whole day project without the correct equipment. We have a tech help desk available to help you on your way to automating your top off system so don't let the thought of a new "Project" scare you! Were here to help, just send us an email and we will send you a solution!Plastic float valve Sealing nut and washer 1 year warranty