Bulkheads allow you to transfer water from one side of an aquarium to the other and allow for traditional PVC plumbing to be connected. In most aquariums, bulkheads are used for drain and return pipes on your display tank but can be used for many other things too.

Some tanks come pre-drilled for bulkheads but may not include them. Knowing the exact size bulkhead that you will need can be a little tricky since the diameter of the hole in your tank does not exactly correspond to your plumbing size (i.e., 2.25” diameter hole does not equate to 2.25” PVC plumbing). If you're going to drill your own tank, it's important to drill the hole in your aquarium the correct size in order to fit the bulkhead you need to match your desired plumbing. 

Bulkhead Materials

  • ABS Bulkheads – By far the most common type of bulkhead used and are very reliable.
  • Schedule 80 Bulkheads – Heavy Duty bulkheads that can be re-used and come with a nut that is much easier to install and remove if required.  Schedule 80 bulkheads do need a slightly larger diameter hole than ABS bulkheads.

Bulkhead Configurations

All bulkheads come in a Female x Female configuration and all fittings or pipes will be attached to the interior of the bulkhead. The threads on the outside of the bulkheads are made for the retaining nut to be threaded onto only. The external threads will not accept any type of plumbing fittings.

  • Slip x Slip – Requires the use of Slip type plumbing fittings and PVC cement.
  • Thread x Thread – Requires the use of NPT Threaded PVC fittings.           
  • Slip x Thread – The in-tank side of the bulkhead will demand the use of PVC Slip type fittings and the exterior will need NPT Threaded PVC fittings.
  • Thread x Slip - The exterior side of the bulkhead will require the use of PVC Slip type fittings and the interior in-tank side will require NPT Threaded PVC fittings.

Selecting a Bulkhead

  1. Measure the diameter of the hole in your aquarium in inches or millimeters.
  2. Using the chart below match up the properly sized bulkhead for your hole.*
  3. Choose the appropriately sized ABS or Schedule 80 bulkheads for your tank.

*There are some cases when you can use multiple sizes of bulkheads because the diameter of the hole fits both and in those instances, we suggest using the largest bulkhead that will fit properly.

Bulkhead Size                          

Maximum Hole Size

Minimum Hole Size

PVC Plumbing Size

1/2" ABS Bulkhead



½” PVC or ½” NPT Threads

3/4" ABS Bulkhead



3/4” PVC or 3/4” NPT Threads

1" ABS Bulkhead



1” PVC or 1” NPT Threads

1 1/4" ABS Bulkhead



1 1/4” PVC or 1 1/4” NPT Threads

1 1/2" ABS Bulkhead



1 1/2” PVC or 1 1/2” NPT Threads

2" ABS Bulkhead



2” PVC or 2” NPT Threads

1/2" Sch 80. Bulkhead



½” PVC or ½” NPT Threads

3/4" Sch 80. Bulkhead



3/4” PVC or 3/4” NPT Threads

1" Sch 80. Bulkhead                



1” PVC or 1” NPT Threads

1 1/4" Sch 80. Bulkhead



1 1/4” PVC or 1 1/4” NPT Threads

1 1/2" Sch 80. Bulkhead        



1 1/2” PVC or 1 1/2” NPT Threads

2” Sch 80. Bulkhead



2” PVC or 2” NPT Threads

Example: If your hole diameter is 1.75” then you will want to use a ¾” ABS Bulkhead, or you could choose between the ½” and ¾” Schedule 80 Bulkheads.

How To Install A Bulkhead

  1. With the bulkhead in your hand unscrew the retaining nut that comes pre-installed on the external threads of the bulkhead.
  2. Clean both sides of the hole in your tank and the bulkhead for any foreign debris or objects that may affect the seal of the bulkhead's O-ring.
  3. With the O-ring against the flange side of the bulkhead, install it with the flange inside the tank, and the external threads are sticking out of your tank. The bulkhead should fall into the hole with no resistance. Any resistance on the bulkhead means the bulkhead is too large for the hole in the aquarium.
  4. While holding the bulkhead screw on the retaining nut. The retaining nut should be installed hand-tight, and the bulkhead should not be allowed to move. (Overtightening of the retaining nut may cause damage to the bulkhead and/or aquarium)

If you have any other questions or need further help contact the reefing experts in our customer service department at 763-432-9691.

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