Aquarium Plumbing Glossary

  • FPT - Female pipe thread
  • MPT - Male pipe thread
  • Slip - Smooth surface for gluing PVC pipe
  • Hose Barb - Barbed fitting designed to make a water tight connection with flexible vinyl tubing
  • PVC Pipe - Polyvinyl chloride, a rigid plastic piping used for many plumbing applications
  • Flexible PVC - Plastic pipe similar to PVC with the added benefit of flexibility
  • Vinyl Tubing - Flexible tubing made of vinyl
  • Teflon Tape - Tape made out of Teflon used for wrapping around threaded plumbing connections to ensure a watertight seal
  • I.D. - Inner diameter
  • O.D. - Outer diameter
  • U-Tube -  A U-shaped rigid pipe used to secure vinyl tubing to your aquarium
  • Flow Accelerator - A special type of nozzle used to increase water flow
  • Impeller - A wheel of blades—usually attached to a magnet—inside a water pump used to move water through the pump as it spins

Aquarium Plumbing Guide


Threaded Bulkhead

Bulkhead fittings allow you to make a sealed connection into a container such as an aquarium or sump. The fittings are designed to be installed through your container and sealed with a rubber gasket and nut via a hole drilled through the container.

Each side has either a standard threaded connection for use with threaded plumbing parts or slip connections for gluing PVC pipe and fittings into the bulkhead. You will always attach your PVC or fittings to the inside of the bulkhead. The threads on the outside of a bulkhead are for use only with the sealing nut mentioned above when you first install the bulkhead.

Slip Bulkhead

Bulkheads are measured based on the inside connections. Therefore, a 1" double-threaded bulkhead fitting will work with 1" standard threaded plumbing parts. You will also notice a "hole size" which is the required diameter of the hole you need to fit the bulkhead through the wall of your container. This hole size is very important when choosing bulkheads in order to fit a pre-drilled sump or aquarium.

Bulkheads are most commonly used for attaching external pumps to your sump and installing drain or return lines into a drilled aquarium or container.

Hose Barb Fittings

Hose Barb Fitting

A hose barb fitting is designed to make a water tight connection with flexible vinyl tubing from a pump, pipe or bulkhead. The fittings will be barbed to help keep them sealed inside the vinyl tubing. Hose clamps should be used on the outside of the tubing to ensure the tubing stays in place when installed on the barbed end of this fitting.

The fittings come with threads or slip fittings for easy connection with bulkheads, PVC pipe fittings or pumps.

The sizes advertised correspond to the inner diameter of the tubing that fits the barb end along with the standard pipe size of the thread or slip connection. For example, a ¾" MPT x ¾" Insert has ¾" male pipe threads for connection on one side and works with ¾" inner diameter flexible vinyl tubing on the other. It’s important to utilize the correct size hose barb to ensure all your tubing connections are watertight and free of leaks.


Hose Clamps

The most commonly used tubing in the aquarium hobby is flexible vinyl tubing. Flexible vinyl tubing comes in either clear or black color and is easily plumbed using a hose barb mentioned above. Flexible vinyl tubing can kink if you are trying to make 90° corners, so be careful when plumbing in tight spaces. This tubing is best used for applications up to 1". The flexible vinyl tubing we carry has a thick wall to help prevents kinks. This type of tubing is measured based on the inside diameter. Be sure to match your pump connection size accordingly and always use a hose clamp to secure the connection.


Flexible Vinyl Tubing

Flexible PVC and Ultra Flex Pipe are flexible tubing made out of PVC plastic. They will work with most any slip-style PVC fittings and standard PVC cement. This style of tubing is available in sizes up to 2" and is measured based on the inside diameter. There are many benefits to using this type of flexible tubing. It allows you to create a clean, permanent plumbing system that reduces pressure on your pumps. It also allows you to form angles that would not be possible with rigid PVC pipe. This type of tubing is not compatible with hose barb fittings and will need to be glued in place using slip fittings.


Overflow Strainer

We have a couple of different strainers available. We have the standard overflow strainers designed for aquarium drains to prevent debris from entering or blocking the drain. They are available with either standard size slip or threaded connections as with most plumbing parts.

Suction screens have a smaller screen/grid to allow for finer filtering of debris and are nice for connecting external or submersible pumps. They can be installed on the connection to prevent debris from entering your pump. They are also available with standard size slip or threaded connections. Just be sure to keep them clean to avoid restriction on your pumps. These can also be used for drains but should be kept clean as they will more easily clog compared to the overflow strainers mentioned above.


Loc-Line Ball Socket Flexible Tube

Loc-Line is a brand name flexible piping that utilizes ball and socket joints to accomplish permanent angles in your piping. This is generally only utilized inside the tank as a nozzle for the return water and can be angled to suit your rock-work or aquascape. It’s useful to help spread out your return flow and provide flow to multiple areas of your tank.

This type of piping is modular and can be expanded to suit most any situation. Loc-Line pliers, available in ½" and ¾" sizes, make it easy to assemble multiple parts. With the use of the male threaded connector, you can easily attach to any female threaded connection such as a bulkhead or return U-Tube.

Ball Valves and Gate Valves

Ball Valve

Ball valves and gate valves are simply shut-off valves that allow you to block water from entering or flowing through your plumbing. They also can help to regulate your rate of water flow through your pipes or tubing.

Ball valves are nice when you need to shut off water flow to a particular area of your plumbing. The valves will quickly block the flow with a simple 90 degree turn of the handle. They are easily plumbed inline using threaded or slip connections.

Gate valves utilize a wheel that slowly closes a gate inside the valve giving you a more precise control when attempting to control the flow of water. The valve requires multiple turns in order to close completely and is best used with rigid or flexible PVC.


Union Fitting

A PVC union will provide you with a removable connection in your plumbing. These are very useful when plumbing aquariums as it allows you to disconnect and remove equipment or valves for maintenance. The valves can be glued or threaded into place and should be installed before and after all your valves and pumps. You can then easily unthread the union and remove your pump/valve with ease. Some valves and pumps even come with a union attached making maintenance easy.

Swing Check Valve

Check Valve
Check valves are used as a one-way flow valve designed to allow water to flow only one direction through your plumbing. When your return pump is switched off, tank water can back siphon down your return plumbing and overflow your sump or water reservoir. These one-way check valves will prevent this from happening.

The valves we carry have no metal parts and should be cleaned regularly to ensure proper function. If not cleaned, the valves can fail and become unreliable. They utilize a single flap with rubber seal in order to block the water flow.

The valves are typically plumbed inline after your return pump. They come with standard slip or FPT connections and with or without unions. The union allows you to remove the valve for easy cleaning. They can be used in a number of other plumbing situations as well, but this is the most common use for aquariums.


What kind of PVC glue is safe for use with my aquarium?

Most standard PVC cements are safe. Just be sure to let it cure/dry completely before running water through the pipes. Primer is not always necessary, but it is a good idea for larger systems and high pressure applications.

My external pump is leaking. What should I do? 

First, check your pump connections to ensure they are tight and use Teflon tape if needed. Then wipe the pump clean and attempt to locate the leak. Every pump is different, so you may simply need to replace a seal. Once you find the leak, you can typically purchase replacement parts online from us and even have them shipped overnight. If the pump leak is complicated and you need help troubleshooting, contact us! Tech support is always free and we’ll do our best to help you diagnose the problem and find an appropriate solution.

My pump stopped moving water. What happened?

First, unplug the pump and disconnect it from your plumbing. Then remove the impeller cover and inspect the impeller for any cracks or damage. Also inspect the impeller housing for any debris or damage. Clean both the impeller cover and impeller thoroughly with an aquarium cleaning kit to remove any build-up.

Proceed to reseat your impeller, assemble the impeller housing and reattach to your aquarium. Following this sequence solves the majority of pump problems if there are no obvious signs of damage found. If you find any damage upon inspecting the pump, do not attempt to use the pump or you could damage the motor and/or void your warranty. We carry replacement impellers for many of the pumps we carry or you can contact the manufacturer directly if your pump is under warranty.

Can I use a 90° elbow to feed my external pump with water from my sump?

No, this is never a good idea as this can create cavitations, trap air and then burn out your pump.