We use the small-end (male-end) and large-end (female-end) method of connecting the components. This is similar to the way plumbing fittings are connected. Fittings and small-end couplings are male-end to slip into pipe and flexhose. A large-end coupling (COU2) is used to make fitting-to-fitting connections. A small-end coupling (COUP) is used to connect sections of pipe. Click here for our couplings. Secure the connection with pop-rivets and silicone caulking. Wipe the silicone around the outside of the connection. By making a chemical bond, the silicone makes the connection airtight. Later if you wish to change your system, you can cut the silicone using a razor blade. This allows easy removal of the fitting.