If you've never worked with PVC, the thought of plumbing an aquarium can feel overwhelming. I remember being new to the hobby a few decades ago and wondering how to connect some braided vinyl tubing to my overflow box. Turns out, I just didn't know what a spigot x barb fitting was!
Armed with the right knowledge and planning, just about anyone can build custom plumbing for their saltwater aquarium.
Before you touch your first piece of PVC, it's important to have an idea of what the goal is.
Water starts in the aquarium, enters an overflow box, flows down into the sump, moves through the filtration chambers, and reaches the return pump.
The return pump then sends the water back up to the display tank, where the process starts again.
The first step in the process is water draining down to the sump, so let's start by talking about the three common drain styles.
Click any diagram below to view a larger version
A Durso Standpipe uses a single drain with a small hole at the top of the assembly to prevent siphoning. It's the most straightforward drain type used in the hobby and is used in many of the big-box store "Reef-Ready" aquarium systems.
Pro:
Cons:
A Herbie style overflow is the sweet spot for most reef keepers. It uses two drains where one is tuned with a valve to a full siphon and the other acts as a secondary backup drain. Because the water is traveling down the plumbing without mixing with air, it's ultra quiet.
Pro:
Con:
A Bean Animal drain is very similar to the Herbie drain discussed above, but also includes a stand-alone emergency drain. If everything goes to plan, this emergency drain should never see water. It's only there in the event of a clog in one of the other two drains.
Pro:
Con:
Fun Fact: The Bean Animal drain style was made popular by a hobbyist that goes by the username "BeanAnimal" on the reefing forums.
Learn More: In-Depth Guide to Durso, Herbie, and Bean Animal Drains
Tip: For aquarium projects, consider using clear primer instead of purple for a cleaner look.
Before gluing anything, sit down with pencil and paper and sketch out your plumbing design. This is a great way to make sure you have the right number of fittings, valves, and other parts. The exact layout will depend on the location of your overflow, sump, return pump, and bulkheads.
The parts listed above will vary based on your specific plumbing project. If you're not familiar with plumbing parts, review our Complete Guide to Saltwater Aquarium Plumbing Parts.
For this aquarium, we're building a Herbie-style drain with a full siphon primary drain and a separate emergency drain.
Don't glue anything yet! We'll start by dry fitting everything together, which just means we're going to assemble the plumbing, but without any PVC cement.
Install a union directly below the primary drain bulkhead. This allows you to disconnect and remove the drain plumbing later without cutting the pipe.
Make sure the union remains accessible once the aquarium and sump are in their final positions.
Install a gate valve below the union in an area that'll be easy to reach when the tank is in its final location (typically under the tank, near the sump). This valve provides the fine control needed to adjust the amount of water moving through the primary drain and tune it into a quiet full siphon.
Run the primary drain into the first chamber of the sump. Keep the route as simple and direct as possible, avoiding unnecessary elbows and sharp turns.
Position the outlet about one inch below the sump's normal operating water level. This helps reduce splashing and noise while still allowing trapped air to easily escape during startup.
Run the emergency drain separately from the primary drain. It should travel directly from the overflow to the sump without a valve or any other intentional restriction.
Position the outlet just above the sump waterline so flowing water can be easily heard. The emergency drain may carry water briefly during startup, but continuous flow means the primary drain needs adjustment or attention.
Important: Never install a valve on an emergency drain. The line needs to remain completely open so it can safely handle the system's flow if the primary drain becomes obstructed.
Once water has a safe path down to the sump, the next step is creating a path back to the display aquarium. Just like the drains, we're going to start by dry-fitting it all together.
Start with a short section of flexible silicone tubing at the return pump. This makes the pump easier to install and remove while also helping reduce vibration.
Connect the tubing to the pump using the appropriate barb fitting and clamps, then transition to rigid PVC.
Run the return line from the pump toward the display aquarium. Keep the plumbing path as direct as possible.
Every fitting and foot of vertical rise adds resistance, so avoid unnecessary elbows and long horizontal runs.
Tip: Make sure the return pump, unions, valves, and other serviceable parts remain easy to reach.
If the aquarium has two return outlets, install a tee to divide the return plumbing into two branches. Alternatively, you may choose to run two return pumps with each pump dedicated to a separate return nozzle for redundancy.
Dry fit both branches and adjust the pipe lengths until they line up naturally with the return bulkheads. The plumbing should not pull, push, or place pressure on the bulkheads.
This step is optional, but can make tank maintenance a little easier.
Install one serviceable check valve before the return line splits. This helps reduce the amount of water that siphons back into the sump when the return pump turns off.
Place the check valve somewhere it can be easily removed and cleaned.
Important: A check valve is not flood insurance. Keep the return outlets close to the surface and make sure the sump can hold all the water that drains back if the valve fails.
Install unions near the return pump, check valve, and other major components.
This allows the equipment and plumbing sections to be removed for cleaning or replacement without cutting the PVC.
I've never met a reefer who regretted adding extra unions, but I've met plenty who wished they had.
Once the drain and return plumbing are completely dry fit, inspect the entire system before taking anything apart.
Make sure the pipes are properly aligned, the valves face the correct direction, and every serviceable component remains accessible.
Draw an alignment mark across each pipe and fitting with a marker.
These marks will help you return every fitting to the correct angle after the dry-fit plumbing is taken apart.
If you've included unions across your setup, this will give you extra flexibility as you'll be able to rotate those sections, even once the rest of the PVC fittings and pipe are glued together.
Tip: Work through one section at a time so fittings and pipe sections do not get mixed up.
Measure each section carefully and cut the PVC as squarely as possible.
An angled cut may prevent the pipe from fully seating inside the fitting and can weaken the connection.
Tip: Use the right tool for the job. A hand-held PVC pipe cutter is the most commonly used tool for this job, but a chop saw is a great way to quickly make ultra-square cuts.
Remove burrs and rough edges from the inside and outside of the pipe. Wipe away any PVC shavings or debris before assembling the connection.
A deburring tool or medium grit sandpaper can make this step a little easier.
Apply primer and cement according to the manufacturer's directions.
Fully insert the pipe into the fitting, give it a slight twist, and line up the alignment marks. Hold the connection together tightly for about 30 seconds so the pipe doesn't push back out.
Continue working one joint at a time until the plumbing is complete, stopping along the way to check that everything is lining up as expected.
Important: PVC cement should only be used on slip connections. Keep it away from threaded fittings, union faces, O-rings, and bulkhead gaskets.
Allow the PVC cement to fully cure according to the manufacturer's instructions before adding water.
Always test new aquarium plumbing with freshwater before adding salt, rock, and sand.
Fill the aquarium and sump while leaving the return pump turned off.
Inspect the following areas for leaks:
Tip: Dry each connection with a paper towel, then check for new moisture. This makes slow leaks easier to spot.
First, make sure your drain valve is set to be fully OPEN.
Turn on the return pump and allow water to circulate through the system.
Note: The water level in the sump will drop, while the water level in the display tank will rise slightly. Be prepared to add more water to the sump to prevent the return pump from running dry.
Inspect every valve, threaded fitting, glued joint, union, and connection around the return pump.
Watch the system for several minutes, since some leaks may not appear immediately.
Set the return pump to the flow rate you plan to use during normal operation.
Slowly close the gate valve in small increments.
After each adjustment, wait for the water level inside the overflow box to stabilize before making another change.
Continue adjusting the valve until:
Turn off the return pump and allow water to drain back into the sump.
Confirm that the sump can hold all the water from the display aquarium, overflow box, and return plumbing without overflowing.
The highest water level reached during this test should remain below the top of the sump.
Turn the return pump back on and make sure the plumbing returns to normal operation without intervention.
Repeat the shutdown and restart process a couple times. Each time, confirm that the primary drain restarts its siphon and the water level settles below the emergency drain.
Temporarily restrict the primary drain to simulate a blockage.
Confirm that the emergency drain can safely handle the aquarium's full operating flow without allowing the overflow box or display aquarium to flood.
Remove the restriction after the test and retune the primary drain.
Tip: Test the system like something is going to fail. It's much better to discover a problem with freshwater than after the aquarium is fully stocked.
Adam has been keeping reef aquariums since 2010 and has worked in the aquarium industry for much of his career. He began at Bulk Reef Supply in Customer Service, helping hobbyists troubleshoot problems and build more successful tanks. Today, he writes educational content and product descriptions that help reef keepers better understand saltwater aquariums and make confident decisions. He believes the best tanks are built around what you enjoy, not what’s trending.
Login and Registration Form