One of the main uses for bulkhead fittings is in aquariums. When you need to have a tube pass through the wall of an aquarium, a bulkhead fitting is needed to seal the tank and prevent leakage. For those who need only one or a few such fittings, there are many places to buy them online.
For companies that sell bulkhead fittings, or use them in the construction of aquariums, JT Enterprises in Holiday, Florida, has the best deal for buying them in larger quantities. JT Enterprises actually manufactures these parts locally and sells only to the wholesale market.
If you need some tips on how to install a bulkhead fitting in an aquarium or other tank, there are many helpful videos now on YouTube. Click this link to watch videos on how to install your bulkhead fitting: YouTube Videos – Bulkhead Fitting Installation Tips.