There are several ways to handle outlets with a drop in liner. Our recommendation as the best method is the use of a bulkhead fitting. A bulkhead fitting eliminates the need to fabricate a pass through outlet in the liner and avoids any potential failures of a fabricated outlet.
A bulk head fitting is a connector designed to pass through a wall in a tank and be mounted on a flat surface. The fitting consists of the bulk head, which can be designed with a pipe socket connection or a threaded connection, a gasket, and a locking nut. Bulk head fittings come in a wide range of sizes as well as material choices.
Before installing the liner a hole needs to be cut into the tank wall to the appropriate size to accommodate the bulkhead fitting. With the liner installed a hole needs to be cut into the liner. Install the bulkhead fitting with the gasket in between the liner and the head of the bulkhead fitting. From the outside of the tank attach the locking nut and tighten. Be careful not to over tighten the locking nut as it could cause the gasket to slip underneath the liner and create a leak. With the bulkhead installation complete the accompanying plumbing can be connected and the tank put into service.