In this video we'll cover the various types of check valves, how to use them, and provide some install tips. Check valves are designed to only allow water flow in one direction. They're commonly used on returns to prevent water from siphoning from the tank to the sump. One important thing to note is that ALL of these valves will fail at some point in their lifetime, so it's important to have other forms of redundancy in place for overall return safety. There are 4 primary types of check valves commonly used in our hobby: - Flapper check valve (most common, least expensive) - Flapper check valve with unions - Wye check valve (utilizes a plunger) - Loc-line check valve Which is the best? The answer will be different for everyone and their specific needs. The biggest factor will be how easy it is to replace or clean. The Wye valve is particularly easy to clean; the side of the valve screws off so you can remove the plunger as well as clean the seat of the valve. This makes it not only more reliable but also means the valve is likely going to outlast the life of the tank itself. I would personally select the wye valve every time without a doubt.