There are hundreds of kinds of fittings to connect your pipes together. And if you cannot find it at the big box store, just go online, and you can find VERY unique fittings for any and every situation!
Planning for Fittings: LESS IS MORE – use the least amount of fittings as possible! Remember, every pipe connection causes a turbulence to flow. Every turn causes flow reductions – especially sharp turns. Every elevation change up or down works against flow. Using pipe or hose, try to make the path as flat, straight and as few fittings as possible. For instance, if the beginning and end of the pipe run is a foot below grade, dig the entire path a foot below grade. Do not rise up to a shallow run then dive back down at the end, this up and down path just robbed you of flow. Do not connect pipes together with a union for two short pieces of pipe if you can use a one long one instead. Exception: using a single 90 degree turn will reduce flow more than using two 45 fittings. But using a hose could eliminate the fittings altogether. Lastly, think carefully about where to place controls such as shutoffs, overflows, fill lines, check valves, etc.
Welding Fittings: Plastic pipes and hoses require glue to “weld” (melt) the pieces together. Before gluing, precut and fit all the fittings and pipes together. Take a sharpie (silver sharpie on ABS) and make marks running from the fitting to the pipe. That way when you glue, you will know what orientation they need to be in. Most fittings have a socket joint – a female end that the pipe fits inside of. When using PVC (but not ABS) requires a purple primer as well which cleans and softens the plastic. Ensure there is no debris and swab primer in the socket and on the pipe end. Then, swab the glue in the same manner to both ends. Insert the pipe fully into the socket with a slight twisting motion and align the pipe and fitting to your marks. You will only have 2-3 seconds before the pipe will weld and not move. So plan the order of gluing carefully. Remember to use the proper glue that matches the plastic type (CPVC, PVC or ABS glue). They even have special glues meant for welding two different plastic types together (such as PVC to ABS).
Removable Fittings: Where the piping or hoses meet a component, you don’t want to permanently glue the plumbing to it. You need a way to remove components such as pumps, filters or valves. The most common fitting is a slip union. It has an O-ring between the parts. Unscrewing this connection allows the pipe to be separated. Another important fitting is a bulkhead. This allows a waterproof connecting through a component. It has a gasket and threads on the outside of the fitting AND it has internal socket threads. Some fittings have threaded ends OR you can buy male or female threaded ends to glue into a socket. Note: Use Thread Sealant (also known as Pipe Dope), not Teflon tape, on your threaded connections.
Shutoff Valves: Sometimes you need a way to divert water from one place to another. A shutoff valve is needed. There are two major kinds of shutoffs: Ball and Gate valves. Balls are the most common and very reliable. It is a large ball with a hole through it. As you turn the ball, the water can flow through it. The other is a gate valve. This is a handle you must crank to close or open. OR sometimes, it is a fence that you shove down into the pipe or pull up. I have had better luck with ball valves and they never leak. However, they can be difficult to turn. There are lubricants that can help with this or a strap wrench.
Check Valves: Pumps usually need one of these on the discharge side. This is a special valve that only lets the water flow in one direction. It consists of a trap door that the water from the pump can push open, but if the pump stops, the water above in the pipe will shut the trap door preventing it from flowing back to the pump. This is important as this could damage the pump or completely drain a component.
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