Bulkheads & Uniseals
Bulkhead fittings create a secure, watertight connection between your aquarium, overflow, sump, and plumbing system. You can glue PVC Pipe or thread adapters and fittings directly into the bulkhead. Bulk Reef Supply carries black ABS aquarium bulkheads in popular sizes and configurations, including Slip × Slip, Slip × Thread, Thread × Slip, and Thread × Thread.
Bulkhead and Glass Drill Bit Sizing Guide
Use the chart below to compare ABS bulkhead dimensions and match each bulkhead with the correct diamond-coated glass drill bit. Bulkheads are identified by the size of pipe they connect to—not by the larger diameter of the hole drilled through the aquarium.
The dimensions below apply to all slip and thread configurations.
Important: These dimensions apply to the listed Bulk Reef Supply ABS bulkheads in all configurations. Always verify the required installation-hole size on the individual product page before drilling.
| Bulkhead | A — Head Diameter | B — Full Height | C — Body Diameter | Hole Size | Glass Drill Bit |
|---|---|---|---|---|---|
| 1/2" ABS Bulkheads | 44 mm / 1.72" | 43 mm / 1.69" | 27 mm / 1.06" | 30 mm / 1.18" | 30 mm |
| 3/4" ABS Bulkheads | 52 mm / 2.04" | 50 mm / 1.98" | 34 mm / 1.33" | 35 mm / 1.38" | 35 mm |
| 1" ABS Bulkheads | 68 mm / 2.67" | 63 mm / 2.48" | 42 mm / 1.65" | 45 mm / 1.66" | 45 mm |
| 1-1/4" ABS Bulkheads | 77 mm / 3.05" | 71 mm / 2.80" | 51 mm / 2.00" | 53 mm / 2.09" | 53 mm |
| 1-1/2" ABS Bulkheads | 86 mm / 3.38" | 73 mm / 2.87" | 59 mm / 2.32" | 60 mm / 2.37" | 60 mm |
| 2" ABS Bulkheads | 98 mm / 3.85" | 73 mm / 2.87" | 72 mm / 2.83" | 75 mm / 2.96" | 75 mm |
BRStv: How To Drill Glass Aquariums
Bulkhead Fitting FAQs
What is an aquarium bulkhead fitting?
A bulkhead fitting creates a secure, watertight plumbing connection through the wall of an aquarium, sump, reservoir, or other container. It allows PVC pipe, fittings, drains, and return lines to pass through the wall without leaking.
Does a 1-inch bulkhead require a 1-inch hole?
No. Bulkhead fittings are identified by the size of the pipe they connect to, not by the diameter of the hole required for installation.
A 1-inch bulkhead requires a hole larger than 1 inch. Always check the product description or bulkhead sizing chart for the exact drill-hole diameter before drilling.
How do I choose the correct bulkhead size?
Choose a bulkhead based on the nominal size of the PVC pipe or fitting you plan to connect. For example, a 1-inch bulkhead is designed to connect to 1-inch PVC plumbing.
You should also consider the desired flow rate, available installation space, and the existing hole diameter if the aquarium or sump is already drilled.
What do slip and threaded bulkhead connections mean?
Bulkhead fittings are available in several connection configurations:
- Slip × Slip: PVC pipe or fittings are glued into both sides.
- Thread × Thread: Threaded fittings connect to both sides.
- Slip × Thread: The flange side is slip and the rear side is threaded.
- Thread × Slip: The flange side is threaded and the rear side is slip.
The first connection type refers to the flange or front side. The second refers to the rear or retaining-nut side.
Should I choose a slip or threaded bulkhead?
Slip connections create a permanent connection using PVC primer and cement. They are often preferred when a strong, compact, and reliable connection is needed.
Threaded connections can be removed or reconfigured more easily, but they must be installed carefully to avoid overtightening or damaging the fitting.
Where should the bulkhead gasket be installed?
The gasket should always be installed against the flange side of the bulkhead, regardless of whether the flange is positioned inside or outside the aquarium.
Do not place the gasket against the retaining nut. The gasket and the surface it seals against should be clean, smooth, and free of debris.
How tight should a bulkhead fitting be?
Tighten the retaining nut by hand until the gasket is evenly compressed and the bulkhead is secure. Avoid excessive force, as overtightening can deform the gasket, damage the bulkhead, or place unnecessary stress on the aquarium glass.
Do bulkhead fittings need silicone sealant?
In most installations, silicone sealant is not required. The gasket is designed to create the watertight seal.
Adding silicone can make future removal more difficult and may prevent the gasket from seating correctly. Follow the bulkhead manufacturer's installation instructions.
Can I install a bulkhead on a curved surface?
Bulkheads should be installed on a flat, smooth surface so the gasket can compress evenly. Installing one on a curved, uneven, or damaged surface may prevent a proper seal and increase the risk of leaks.
What is the difference between ABS and Schedule 80 bulkheads?
ABS bulkheads are lightweight, economical, and commonly used for standard aquarium plumbing installations.
Schedule 80 bulkheads have a heavier-duty construction and are often chosen when additional strength or durability is preferred. Always confirm the required hole diameter because similarly sized ABS and Schedule 80 bulkheads may require different hole sizes.
Can I reuse an existing drilled hole for a new bulkhead?
Yes, provided the existing hole matches the required hole diameter for the new bulkhead and the surrounding surface is smooth and undamaged.
Measure the opening carefully before ordering. Bulkheads with the same nominal pipe size can require different hole diameters depending on their material and construction.
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