Plumbing Nomenclature: Understanding Aquarium Plumbing Parts
Don RobertsUnderstanding Aquarium Plumbing
Sometimes, just planning on how to connect all the plumbing parts of your aquarium filtration system is difficult enough without having to translate the unique language of plumbing parts. This article will attempt to clarify some of the confusion.
When dealing with flexible tubing, we are almost always talking about the size of the inside of the tubing, also known as the I.D. (Inside Diameter). Some manufacturers will also list the O.D. (Outside Diameter) of the tubing, but this is rarely important for aquarium purposes. Eheim is one of the few who list both, i.e. 16mm/22mm (I.D./O.D.) on their flexible tubing. Where it can get complicated is fitting the flexible tubing to the proper size PVC hose barb. While it is possible to fit ½” ID flexible hose onto a ½” Hose Barb, you will usually need to heat up the flex hose to make it pliable enough to slip on the barb. The plumbing world rarely uses 5/8” I.D. tubing, but this is very common in the aquarium tubing world. Fortunately, 5/8” I.D. tubing fits really well on a ½” Hose Barb, just be sure to use a ¾” Nylon Hose Clamp. Yes, we are placing a 5/8” I.D. hose on a ½” barb and tightening it in place with a ¾” clamp. What could be confusing about that!?!
When dealing with rigid PVC piping, once again the “size” of the PVC part is listed for the size of the hole of the pipe. A 1” PVC pipe will have an I.D. of 1”, but the pipe will be 1 ¼” on the outside. A 1” bulkhead or elbow or coupler is designed to work with other 1” PVC pipe fittings, meaning that a 1” PVC pipe will fit into the opening of the 1” bulkhead, elbow or coupler. The actual opening of these fittings will be 1 5/16” I.D. to let the 1” PVC pipe to slide right in. This type of fitting is called a Slip Fit connection, the pipe slips into place and is usually glued into the fitting. For less permanent connections, you can have FPT (female pipe thread) and MPT (male pipe thread) fittings that will screw into each other to make a connection. To connect one of these to a piece of PVC pipe would require one side to be a slip fitting and the other to be one of the screw fittings. This would be listed as a Slip/FPT or Slip/MPT fitting. To convert from PVC pipe to flexible tubing will require a part called an Insert Adapter. While there are Slip/Insert adapters, most of the time you will convert from PVC pipe to a screw thread, Slip/FPT, then attach a screw thread to hose barb, MPT/Insert adapter.
Bulkheads are listed as a Slip/Slip or standard bulkhead, or as either a single or double (female) threaded bulkhead. All bulkheads have a flattened face with a mouth and then a long tail pipe. It is the inside of the mouth and tail that are either a slip fit or a FPT fitting. All bulkheads have screw threading on the outside of the tail section, but this is there for the lock nut to screw into position to keep the bulkhead in place and water tight. It is not used to connect to other plumbing fittings.
Common Plumbing Definitions
- SLIP FIT: A smooth opening to allow rigid PVC pipe to slide into the fitting
- MPT: Male Pipe Thread, screw threading on the outside of the adapter
- FPT: Female Pipe Thread, internal screw threads on the adapter
- SLIP Bulkhead: Both the mouth and the tail have SLIP FIT to allow the PVC pipe to slide into position and be glued into place
- Single Threaded Bulkhead: Just the mouth has FPT screw threads, the tail is still SLIP FIT
- Double Threaded Bulkhead: Both the mouth and the tail have FPT screw threads
- Insert Adapter: A hose barb to allow flexible tubing. May have SLIP FIT, MPT or FPT on one end and the barb on the other to convert from PVC pipe to flexible tubing
Reader Comments (3)
Aquarium plumbing and tubing parts allow you to customize your aeration, filtration or water circulation setup. Aquarium plumbing systems are connected using either soft plumbing or hard plumbing methods.
The most important step in plumbing the aquarium is planning out its design. Water circulation is an essential and often misunderstood part of successful aquarium keeping.
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