A Complete Guide to Saltwater Aquarium Plumbing Parts

Ball Valve

A ball valve is a simple on/off valve that uses a rotating ball with a hole through the center to control water flow. While inexpensive versions from the local hardware store can work in a pinch, they often become stiff and nearly impossible to turn over time. High quality options like Cepex ball valves are designed specifically for aquarium and industrial use, offering smoother operation, better seals, and long-term reliability.

Common Uses:

• Shutting off water flow to equipment like pumps or reactors for maintenance
• Isolating sections of plumbing for maintenance or repair
• Providing basic flow control where precise adjustment is not needed

Gate Valve

A gate valve uses a sliding gate to gradually open or restrict water flow. Unlike ball valves, which are best for quick on/off control, gate valves excel at making fine adjustments. This makes them a favorite in reef tank plumbing where precise control is needed, especially on drains. Spears gate valves are some of the highest quality available and what we typically use and recommend.

Common Uses:

• Fine-tuning siphon drains in a bean animal or herbie overflow setup
• Creating precise flow control where small adjustments make a big difference

Wye Check Valve

A Wye check valve is a one-way valve that allows water to flow in only one direction and prevents backflow when pumps are turned off. The “Wye” shape makes it easy to install in-line without taking up much space. They have a removable plunger that can be cleaned easily without having to remove the main body of the check valve from your plumbing. A check valve should never be the only line of defense to prevent your sump from overflowing during a power outage, but they can be useful tools to keep the water level up in the main display during maintenance. In tanks where corals are growing near the surface, this can be even more important.

Common Uses:

• Preventing back siphon from display tanks into the sump when return pumps are off
• Adding peace of mind in systems where plumbing design alone cannot eliminate backflow

In-Line Check Valve

An in-line check valve, sometimes called a swing or flapper style check valve, is the most common type of check valve used in the aquarium hobby. It works by closing a flap when water starts flowing the opposite direction and seals the opening so water cannot flow any further. If you're installing one of these on your system, install unions on each end so it can be removed for cleaning. Some models include built-in unions.

Common Uses:

• Preventing back siphon from display tanks into the sump when return pumps are off
• Adding peace of mind in systems where plumbing design alone cannot eliminate backflow

Bulkhead

A bulkhead is a fitting that allows you to create a watertight pass-through in your aquarium, sump, or reservoir. It consists of a flange, gasket, and nut that sandwich the tank wall to form a seal. Bulkheads make it possible to connect internal plumbing to external plumbing without leaks. They come in both slip and threaded options, depending on what you need for your project.

Common Uses:

• Plumbing an internal overflow setup to an external sump
• Plumbing a return line through the glass or acrylic for a sleek installation

Tips:

• Always install the gasket on the flange side, typically inside the tank (the wet side)
• Hand-tighten the nut, then add just a quarter turn more
• Never attach plumbing to the exterior threads; those are only for the installation nut

Uniseal

A Uniseal is similar to a bulkhead, allowing you to create a watertight pass-through in a solid surface. The difference is that Uniseals are designed for curved surfaces like buckets or water storage containers where standard bulkheads will not seal properly. They are made from a single piece of flexible rubber, which grips tightly around PVC pipe to form a reliable seal without multiple parts.

Common Uses:

• Plumbing PVC pipe to a water storage container in a saltwater mixing station
• Any application that requires adding hard plumbing to a curved surface

Tip: Do not use Uniseals to attach plumbing to the aquarium itself; a bulkhead is a better option.

90° Elbow

A 90° elbow changes the direction of PVC plumbing at a right angle. It is one of the most common fittings in aquarium plumbing and is available in multiple connection types.

Common Configurations:

• Slip x Slip: Both ends accept PVC pipe to be glued
• Slip x Thread: One end accepts glued PVC; the other end has female threads
• Thread x Thread: Both ends have female threads
• Slip x Street: One end accepts PVC; the other end glues directly into another fitting

45° Elbow

A 45° elbow changes the direction of PVC plumbing at a 45-degree angle. It is less common than 90° elbows but useful when plumbing needs to shift direction gradually or line up with equipment at an angle.

Common Configurations:

• Slip x Slip: Both ends accept PVC pipe to be glued
• Thread x Thread: Both ends have female threads
• Slip x Street: One end accepts PVC; the other end glues directly into another fitting

Union

A union lets you easily disconnect a section of plumbing without cutting pipe. It consists of two halves joined by a threaded collar, creating a watertight seal with an O-ring. Unions make maintenance and equipment changes much easier.

Common Configurations:

• Slip x Slip: Both ends accept PVC pipe to be glued
• Thread x Thread: Both ends have female threads
• Slip x Thread: One glued end and one female threaded end

Coupler

A coupler is a straight fitting used to join two pieces of PVC pipe. They are simple and handy for extending runs or repairing sections of pipe.

Common Configurations:

• Slip x Slip: Both ends accept PVC pipe to be glued
• Thread x Thread: Both ends have female threads

Reducing Coupler

A reducing coupler joins two PVC pipes of different sizes in a straight line. One end is larger and the other is smaller, allowing you to step pipe diameter up or down.

Common Configurations:

• Slip x Slip: Both ends accept PVC pipe to be glued
• Thread x Thread: Both ends have female threads

Reducing Bushing

Similar to a reducing coupler, a reducing bushing transitions between different pipe sizes, but it is inserted into another fitting rather than onto PVC pipe. This reduces the output size of the fitting it is glued or threaded into, saving space.

Common Configurations:

• Spigot x Slip: Glues into a slip fitting and accepts smaller PVC
• Spigot x Female Thread: Glues into a slip fitting and accepts a smaller male thread
• Thread x Thread: Reduces the size of a female threaded fitting

Tee

A tee fitting splits a single PVC pipe run into two directions. The fitting has three openings arranged in the shape of a “T,” with one inlet and two outlets.

Barbs

A barb fitting allows flexible tubing to connect securely to your plumbing. The ridged barb end grips the inside of soft tubing, while the other side may be threaded, slip, or another barb to connect additional tubing. They are inexpensive, easy to install, and useful anywhere flexible connections are needed. For the best seal and long-term reliability, pair barb fittings with a hose clamp.

Most Popular Barb Types:

• Straight Barb x Male Thread: Connects soft tubing to a female threaded PVC fitting
• Straight Barb x Spigot (street): Connects soft tubing to a slip PVC fitting

Loc-Line

Loc-Line is a brand of modular plumbing fittings that snap together to create adjustable flow paths. Most often, Loc-Line is used on return lines coming out of bulkheads, where its flexible segments let you direct flow exactly where you want it in the display tank. The pieces hold their shape once adjusted.

Popular Loc-Line Pieces:

• Male NPT Connector: Connects a Loc-Line segment to a female threaded fitting (usually a bulkhead)
• Loc-Line Segments: Flexible modular pieces that snap together
• Flare Nozzle: Aims and spreads flow in a specific direction

Random Flow Generators

Random Flow Generators (RFGs) are nozzle attachments that create a randomized, turbulent pattern without moving parts or electronics. By reshaping water as it leaves the return line, they reduce the jet stream effect of standard nozzles and help produce more natural flow. Vivid Creative Aquatics (VCA) offers reef-safe models in multiple sizes with adapters for Loc-Line, slip, threaded, and even metric plumbing.

1/2" NPT x Push-Connect Adapter

While push-connect fittings are often associated with RO systems, this adapter makes it easy to go from standard hard plumbing to 1/2" RO-style tubing. It is a simple way to plumb a BRS reactor to a pump or manifold.

Push-Lock Coupling

Push-Lock fittings are quick-disconnect couplings that make equipment easy to remove or service without cutting or unthreading plumbing. They seal automatically when disconnected, helping prevent spills during maintenance. These are less common than standard PVC connections but very useful where gear is removed often.

Common Uses:

• Quick disconnects for pumps or reactors that need regular maintenance
• Water change or mixing station connections that are swapped regularly

Metric to Standard Adapters

Metric to standard adapters connect plumbing parts made to metric sizes with standard Schedule 40 or Schedule 80 PVC used in the U.S. They are most often used when modifying an aquarium kit that uses metric plumbing and are available as unions or couplers.

PVC Pipe

PVC pipe is the standard material used for hard plumbing a saltwater aquarium and is available in several types. Schedule 40 is the most common option, while Schedule 80 provides added strength with thicker walls and a dark gray color. Colored PVC is also available to customize the look of your plumbing.

Braided Vinyl Tubing

Braided vinyl tubing is a form of soft plumbing reinforced with a cross-pattern of fibers for extra strength. It is the easiest way to plumb a tank: connect it with barb fittings and secure with hose clamps. The reinforcement makes it far less likely to kink than standard clear vinyl while still routing around tight spaces.

Black Vinyl Tubing

Black vinyl tubing is similar to clear vinyl but blocks light from entering the line, which helps prevent algae growth inside the tubing. Like other soft plumbing, it connects quickly to barb fittings with hose clamps and keeps maintenance simple.

Silicone Tubing

Silicone tubing is very flexible and great for reducing vibration and noise. Use a short run between a return pump and hard plumbing to dampen pump vibrations for a quieter system. It is not recommended for drain lines because it can kink easily under its own weight or when bent too sharply.