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A bulkhead connector, also called a bulkhead fitting, lets you make a watertight pipe connection through the wall of a rain barrel, water tank, IBC tote, or cistern. It is commonly used for outlets, drains, overflows, pumps, and connecting two tanks.
The basic job is simple: drill the correct-size hole, insert the fitting, place the gasket on the correct side, tighten the nut evenly, and connect the pipe without putting too much strain on the tank wall.
The part that causes most leaks is not the fitting itself. It is usually a hole that is the wrong size, a gasket installed incorrectly, an uneven surface, or a fitting that has been overtightened.
What Is a Bulkhead Connector?
A bulkhead connector passes through the wall of a container and creates a sealed connection on both sides.
A typical fitting has:
- A threaded fitting body
- A sealing gasket
- A retaining nut
- Internal or external pipe threads, or another connection for tubing or pipe
The gasket seals against the tank wall while the nut holds the fitting in place.
Bulkhead fittings are useful because you do not have to glue a pipe permanently into the tank wall. Depending on the fitting style, you can often remove or replace connected plumbing later.
Choose the Connection Location First
Before drilling the tank, decide what the fitting will do.
For a bottom outlet, place it low enough to use most of the stored water but high enough that sediment is less likely to enter the outlet.
For an overflow, place it near the maximum water level. Leave enough room around the fitting for the nut, pipe, elbow, or overflow hose.
For a tank-to-tank connection, both fittings normally need to be positioned so the connecting pipe can run without severe bends or stress.
Also check the inside of the tank. Internal ribs, curves, molded seams, braces, or cage parts can prevent the nut or gasket from sitting flat.
A fitting installed on a smooth, flat section of wall is usually easier to seal.
Check the Bulkhead Fitting Before Drilling
Do not choose the hole size based only on the stated pipe size.
A fitting sold for 1-inch pipe, for example, normally needs a hole larger than 1 inch because the body of the bulkhead must pass through the wall.
Measure the fitting body or follow the fitting manufacturer's required hole diameter.
Also check:
- Maximum wall thickness the fitting can handle
- Type and size of pipe connection
- Gasket location
- Required tightening method
- Whether the fitting material is suitable for your intended water use
If you are working with an IBC tote, also confirm that drilling the container is appropriate for its material and intended reuse.
Tools and Materials
The exact tools depend on the tank and fitting, but a typical installation may require:
- Bulkhead fitting
- Correct-size hole saw
- Drill
- Marker
- Tape measure
- Deburring tool, utility knife, or fine file
- Clean cloth
- Suitable wrench or large pliers if the fitting requires them
- Pipe or hose fittings for the final connection
You may also need pipe-thread sealant or PTFE tape on threaded plumbing connections.
Do not automatically put sealant on the bulkhead gasket itself. The gasket normally creates the seal between the fitting and tank wall. Follow the fitting manufacturer's instructions if lubrication or sealant is specified.
How to Install a Bulkhead Connector
1. Empty the Tank
Do not drill into a full tank.
Water adds a large load to the walls and makes the job difficult to control. Drain the container below the work area, and preferably empty it completely if practical.
Make sure the tank is stable before working on it.
Do not enter a large cistern or enclosed tank to install a fitting. Confined-space entry can be dangerous and should be left to properly trained professionals.
2. Mark the Hole Location
Measure carefully and mark the center of the planned opening.
Check the location from both inside and outside the tank if possible.
Make sure there is enough clearance for:
- The bulkhead nut
- The gasket
- A wrench or hand access
- Connected valves or elbows
- Pipe support
- Nearby tank ribs or framing
Check everything before drilling. Moving the hole later usually means repairing or replacing the tank.
3. Drill the Correct-Size Hole
Fit the proper hole saw to the drill.
Hold the drill as square to the tank wall as possible and drill steadily. Avoid forcing the saw through the plastic.
Thin plastic can grab or tear if the drill is pushed too hard.
For curved tanks, choose the flattest practical location. A severe curve can prevent the gasket from sealing evenly.
4. Clean the Hole
Remove loose plastic and smooth any sharp burrs around the opening.
The edge should be clean enough that it does not cut or distort the gasket.
Do not aggressively enlarge the opening while cleaning it. If the hole becomes too large, the gasket may not have enough surface to seal.
Wipe the area clean before installing the fitting.
5. Install the Fitting and Gasket
Insert the bulkhead body through the hole.
Bulkhead designs vary, so follow the gasket arrangement specified for your fitting. Many fittings use a gasket against the flange side of the tank wall, but you should not assume every fitting is assembled the same way.
Keep the gasket flat.
It should not be:
- Folded
- Twisted
- Pinched
- Partly outside the sealing surface
- Sitting over plastic shavings or dirt
A clean, even gasket surface is one of the most important parts of the installation.
6. Thread on the Retaining Nut
Install the retaining nut from the opposite side.
Start it by hand to avoid cross-threading.
Tighten the nut until the gasket is evenly compressed and the fitting feels secure.
Do not keep tightening simply because more thread is available.
Overtightening can:
- Distort the gasket
- Warp a thin tank wall
- Crack the fitting
- Damage the tank
- Make a leak worse rather than better
Some fittings have a specific torque requirement. Follow it when one is provided.
7. Connect the Plumbing
Once the bulkhead is secure, connect the valve, adapter, hose, or pipe.
The bulkhead seal and the pipe-thread seal are two different things.
The gasket seals the bulkhead against the tank. Thread sealant or PTFE tape may be needed on compatible pipe-thread connections attached to the bulkhead.
Do not use excessive force when tightening the external plumbing. Twisting a valve or pipe hard against the fitting can rotate the entire bulkhead and disturb its gasket.
8. Support Heavy Pipe and Valves
A bulkhead fitting should not carry the weight of a long plumbing run.
Support rigid pipe, pumps, filters, and heavy valves independently when needed.
This is especially important on thin plastic barrels and tanks. Constant sideways force can deform the wall and eventually cause a leak around the fitting.
9. Test for Leaks Slowly
Add a small amount of water and inspect the fitting.
Look around the gasket and tank wall, not just the threaded pipe connection.
If it stays dry, raise the water level gradually until the fitting is under normal operating pressure.
A fitting near the bottom of a tall tank sees more water pressure than one near the top because of the water above it.
If you see a leak, drain the water below the fitting before making major adjustments.
Which Side Should the Gasket Go On?
Explore practical steps for choosing the right bulkhead fitting to verify the relevant trade-offs before the project advances.
There is no safe universal rule for every bulkhead design.
Many common bulkhead fittings place the gasket against the flange side of the fitting rather than under the retaining nut. The flange provides a broad, smooth surface that compresses the gasket evenly.
However, some fittings use different gasket arrangements.
Use the configuration specified by the manufacturer rather than moving the gasket around until the leak stops.
Adding extra homemade gaskets can also create problems if they prevent the fitting from tightening correctly.
Should You Use Silicone on a Bulkhead Fitting?
Usually, a properly installed bulkhead fitting should seal with its gasket alone.
Silicone should not be used as a substitute for:
- The correct hole size
- A flat mounting surface
- The proper gasket
- Correct tightening
Adding sealant can sometimes make later removal more difficult, and some sealants may not be appropriate for every tank material or intended water use.
If the manufacturer specifically calls for a sealant, use one compatible with the fitting, tank material, and intended water use.
For water intended for drinking, every material that contacts the water deserves more careful consideration. Rainwater should not be considered potable simply because the tank and fittings do not leak. Drinking-water systems require suitable collection, treatment, maintenance, and current water-quality testing.
Installing a Bulkhead Fitting Near the Bottom of a Tank
A low outlet makes it easier to drain or pump water from a tank, but placing it at the absolute lowest point is not always best.
Sediment tends to settle on the bottom. If the outlet sits slightly above that layer, less debris may be carried into hoses, pumps, or irrigation lines.
A separate low-point cleaning drain may be useful on larger systems.
Also leave enough clearance below the outlet for a valve and hose connection.
If the tank sits directly on the ground, there may not be room to operate the valve. Plan the outlet before choosing the final tank height or support.
Installing an Overflow Bulkhead
An overflow fitting should allow excess water to leave the tank before water reaches openings that are not designed to handle overflow.
Use a large enough overflow path for the expected inflow. A small overflow can be overwhelmed during heavy rain even if it works during light rain.
Route the overflow somewhere that will not cause:
- Foundation problems
- Soil erosion
- Ponding around the tank base
- Damage to neighboring property
- Water returning toward the tank
Screen openings where appropriate to help keep insects and larger debris out while maintaining enough open area for water to flow.
Installing Bulkheads in IBC Totes
IBC totes require a little extra planning because the plastic container sits inside a metal cage.
Check that the fitting does not interfere with:
- The cage
- The pallet base
- The existing outlet
- Forklift openings
- Nearby structural parts
You should also know what the tote previously contained before using it for harvested water.
A container that held an unknown or unsuitable chemical should not be assumed safe simply because it has been washed.
For drinking-water systems, use storage equipment and components suitable for potable-water applications and follow applicable local requirements.
Connecting Two Tanks With Bulkhead Fittings
Bulkhead fittings are often used to connect rain barrels or storage tanks.
The pipe between them needs enough room to move slightly without pulling hard on either tank wall.
Tank foundations matter too.
If one tank settles lower than the other, a rigid connection can become stressed. Flexible connections or properly supported plumbing may help accommodate small movement, depending on the system design.
Remember that linked tanks can move water between each other. The connection, valves, overflow arrangement, and tank elevations should be planned as one system rather than as separate parts.
Common Bulkhead Installation Problems
The Fitting Leaks Around the Tank Wall
Possible causes include:
- Gasket installed incorrectly
- Dirt under the gasket
- Rough hole edge
- Hole too large
- Curved mounting surface
- Uneven tightening
- Cracked fitting
- Warped tank wall
Drain below the fitting and inspect the seal rather than simply tightening harder.
The Pipe Threads Leak
If water appears at the connection between the bulkhead and a threaded adapter, the bulkhead gasket may be fine.
Inspect the pipe-thread connection separately.
Use the correct thread type and suitable thread-sealing method. Do not force mismatched threads together.
The Fitting Keeps Turning
Hold the fitting according to its design while tightening the plumbing.
If a valve or adapter rotates the bulkhead body, it can disturb the gasket seal.
Supporting the connected plumbing also reduces this problem.
The Tank Wall Bends Around the Fitting
The fitting may be overtightened, the wall may be too thin for the application, or heavy plumbing may be pulling on it.
Do not keep tightening a deformed tank wall.
Relieve the load and inspect the fitting and tank for damage.
Do Not Forget Pipe Size and Flow
A bulkhead fitting affects more than whether the tank leaks.
Its opening size can limit how quickly water moves.
A small fitting may be fine for filling a watering can but restrictive for:
- A pump suction line
- A high-flow irrigation system
- A fast tank transfer
- A large overflow
The smallest opening in the water path can become a flow restriction.
For gravity-fed systems, available pressure is already limited. Unnecessarily small fittings, long hoses, sharp bends, and restrictive valves can reduce flow further.
When to Stop the DIY Job
Installing a fitting in a small rain barrel or accessible plastic tank is often a manageable DIY task.
Professional help is more appropriate when the job involves:
- Large buried cisterns
- Confined-space access
- Pressurized plumbing
- Electrical pumps near water
- Structural modification of a tank
- Household potable-water plumbing
- Uncertain tank materials
- Connections covered by local plumbing rules
Large tanks can also become extremely heavy when full. Make sure the tank and its base are suitable for the water load before filling it.
Frequently Asked Questions
Can I install a bulkhead fitting without getting inside the tank?
Sometimes. Some fittings are designed for installation when you can reach both sides, while others are made for situations with limited internal access. Choose the fitting before drilling the hole. Never enter a cistern or enclosed tank just to reach a nut.
How tight should a bulkhead fitting be?
Tight enough to compress the gasket evenly and hold the fitting securely, but not so tight that the gasket, fitting, or tank wall deforms. Follow the fitting manufacturer's torque instructions when available.
Does the rubber gasket go inside or outside the tank?
It depends on the fitting design. Many bulkheads place the gasket against the flange side, but not all fittings use the same arrangement. Follow the manufacturer's assembly instructions.
Can I use a bulkhead fitting on a curved rain barrel?
Sometimes, but a flat mounting area is better. A strong curve can keep the gasket from compressing evenly and may cause leaks.
Should I put silicone around a leaking bulkhead?
Not as the first fix. Drain below the fitting and check the gasket, hole size, mounting surface, and tightening first. Sealant cannot reliably correct a badly drilled or poorly seated connection.
Can a bulkhead fitting be used for a pump inlet?
Yes, if the fitting and pipe size are suitable for the pump and expected flow. Keep the suction path appropriately sized and avoid plumbing arrangements that can introduce air or excessively restrict flow.
Can I drill a bulkhead hole in a full rain barrel?
No. Drain the barrel below the planned hole, and preferably empty it first. A full container is harder to work on safely and places significant load on the wall.
