How to Connect Hydraulics in a Saltwater Aquarium

How to Connect Hydraulics in a Saltwater Aquarium

Table of Contents

What is the purpose of hydraulics in a saltwater aquarium? 

In saltwater aquariums, the most common way to set up is by having two types of tanks in one system. The upper tank, where the rock and animals are located, serves a display purpose. Meanwhile, the lower, technical tank, known as a sump, is where filtration, heating, and other processes take place.

Water between the upper and lower tanks is constantly in motion. The water from the upper tank flows through an overflow and then enters the sump, from where it is pumped back using a return pump. All these components are connected with a system of pipes, which we call hydraulics.

Which hydraulic components are used in a saltwater aquarium?

90-degree elbow

45-degree elbow

tube elbows


overflow strainer

glass bulkhead fitting


PVC union coupler



mounting brackets for hydraulic installation

Short description of hydraulic components

PVC pipes are, of course, used to guide water in the aquarium according to the plan. Elbows and curves are used to change the direction of the pipes. Here’s a quick tip to use elbows to avoid slowing down the water flow. This is especially important for the return pump’s hydraulics because we don’t want to diminish its power. We use a glass bulkhead fitting in the overflow. 

Where do we start? To begin with, I suggest making a simple sketch to visualize how the hydraulics in the aquarium will look. We need to see the bends clearly. This drawing will help us calculate how many of each hydraulic element we will need. Once we have the list of items to purchase, it’s worth considering or asking someone experienced about the pipe diameter we should use. Generally, I recommend choosing a larger pipe diameter to ensure that we don’t restrict the power of the pumps.

I use the following pipes: 100-300L – 25 mm hydraulics, 300-600L – 32 mm hydraulics, above 600L – I use 40 mm. In larger tanks, 50 mm hydraulics are used, or elements are created doubly. These recommendations should not be taken as exact rules. It all depends on various factors, such as the pump we choose and its connections. Please consider the above suggestions as a starting point and analyze your individual case.

What else will we need for the hydraulic installation?

  • Glue for PVC hydraulics
  • Hydraulic cutting scissors
  • Dry cloth for wiping hydraulics (non-dusting)
  • Fine file for smoothing hydraulics
  • Non-erasable black marker


Installation of hydraulics

Where do we start? I suggest starting with screwing the bulkheads into the overflow. To do this, wipe the glass dry. There should be no dust or sand on it, as this could cause leaks. Typically, there are 3 holes in the overflow (runoff, revision, and return pump). Screw the bulkheads in so that they connect to the glass with a rubber seal from the top. Tighten the screws from the bottom by hand.

In the next step, cut a piece of the pipe and install a ball valve on the overflow. This valve will help us adjust the water level in the overflow. Then, we need to create the entire system of pipe connections so that the runoffs from the water drop and revision end up in the first chamber of the sump, and the runoff through which water will return to the main tank should connect to the return pump. For this purpose, we will need to trim the pipes or use elbows. To ensure stability, we use dedicated brackets – make sure none of the pipes are loose. The pipes entering the sump should be 3 cm below the planned water level in the sump.

Once we’ve created the piping, and all the elements are connected – the pipes are secured in brackets at crucial points, and our piping system looks according to the planned design – we can start gluing the hydraulics.

Gluing hydraulics 

To assemble our trial hydraulic system, we need to mark the connections between elements with lines. This is to determine the position of one element relative to another. In the next step, starting from the bulkheads through the glass, we break down the hydraulics into smaller parts and then glue them. I suggest gradually gluing individual elements, placing them in position, and only then moving on to the next elements. When applying the glue, make sure to spread it evenly. Collect any excess glue with paper to avoid dirtying the elements.

After gluing all the elements together, we need to wait for the glue to dry. The drying time for the glue can be found on its label.

Performing a leak test 

After the glue has dried, we can perform a hydraulic leak test. I suggest starting with the lowest pump power. During the leak test, we need to observe if there are any leaks. If a leak occurs, we have the following options: tighten the element (if possible) or cut out the poorly glued element and insert a new, properly glued assembly. To replace a faulty element, start by cutting it out, then use bulkhead fittings and insert the new assembly into place dry. Finally, proceed to glue it and perform the test again.


It’s worth planning and executing this process well and meticulously testing the finished system. A well-done hydraulic setup will serve us for years.

About the author

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Marek Protasewicz

Reefkeeping has been my passion for over 10 years now. I love learning. The hobby has taught me many valuable lessons, patience being the best example. Combining work and passion is my path. I run Crazy Coral, a marine aquarium shop, for a number of years. Building this business from the scratch I learnt from my own mistakes at a heavy cost.
Later I managed a project aimed at development of methods for quick growth of Corals in non-natural conditions. The project was carried out by Get Sales, Poland. Presently, I am responsible for distribution strategy at Reef Factory, of which I am a co-founder. The company produces smart devices for marine aquaristics. The last projects I have been involved in are Social Reef and ReefPedia.

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