Review on UNISEAL Flexible Tank Adapter Bulkhead Hydraulics, Pneumatics & Plumbing ~ Fittings by Bryan Hill

These things work great on curved surfaces - never had a leak. For larger ones, take a coarse file and BARELY bevel the edge of the pipe and bevel it back about 3/4 inch. Lubricate the inside of the Unisil with silicone. Use a tee at the end of the pipe so there is something to push on. I use them in pond filter tanks and aquariums. With their help, they also made filters from flower pots and liners for air buckets. Also worked on a preformed pond, an old pool sand filter (on the curved part) and one of these filters. I have leaked bulkhead fittings but never had a leak.