Cascade 80 Filter Cartridge 3pk Replacement S. Secure your aquarium or pond plumbing with this durable 1.5-inch Bulkhead Fitting. This essential PVC fitting is designed to create a completely watertight seal through the wall of your tank, sump, or filter system. With its convenient slip-slip connections, it provides a reliable and easy-to-install solution for building custom overflows, returns, and other aquarium plumbing setups. This robust bulkhead ensures a secure connection for your filtration and circulation systems, providing the peace of mind that your aquatic environment is safe and well-maintained.