Valves are essential to controlling the flow of all your plumbing around your tank and sump. Bulkreefsupply.com carries a variety of valves to meet your specific plumbing needs. Choose a needle valve from Hayward or Vertex to fine tune your flow rates - commonly used for calcium reactors. A Swing Check valve is a one-way valve commonly used on return lines to prevent back siphoning. True Union valves are good for maintenance issues because they are easy to remove and replace. Gate valves are used to control flow and ball valves and used to stop and start flow. Two Little Fishies micro ball valves are great for flexible tubing. Use the George Fisher Wye Check Valve for one directional flow and are commonly used on return pump outputs to prevent overflowing in the sump.