Adapters, Bushings & Nipples for Aquariums
A PVC reducer bushing goes into a PVC fitting or pipe to reduce the size on the other end. A PVC adapter changes the type of fitting. A PVC nipple fitting connects two of the same type fitting. While it is best to have the fewest possible fittings sometimes an adapter helps.
PVC fittings are listed according to PVC pipe sizes, not the actual measurement of the part. So, a 1 inch slip elbow does not measure 1 inch but fits onto 1 inch PVC pipe. PVC fittings are categorized by the types of connections they make:
MPT, or male pipe thread, has threads on the outside wall
FPT, or female pipe thread, has threads on the inside wall
A PVC slip fitting, or slip fit, has no threads and connects to PVC pipe
PVC insert fittings, or hose barb fittings, connect to aquarium tubing (not flex PVC pipe)
A reducer fitting reduces PVC size