Aquarium Return Plumbing (Pumps, Nozzles, Check Valves, Calculators)

Image Credit: CC BY 2.5, Link
Image Credit: CC BY 2.5, Link

Aquarium Return Plumbing (Pumps, Nozzles, Check Valves, Calculators)


Plumbing is one of the most important aspects of your reef tank’s performance. It affects not only the quality of your tank’s water but also the health of your corals and other organisms. On top of that, a tank’s plumbing can be the most dangerous if not properly designed and installed. Flooding is one of the worst things that can happen to an aquarist but if you are prepared for equipment failure then your chance of significant flooding should be significantly reduced.

Aquarium return pump and other plumbing details

Your tank is a closed-loop system; there is the main tank, sump with the return pump, and your overflow. The water will flow through all of these designations thanks to the power of return pumps. The tank return pump is what makes the entire system keep moving so it is a good spot to start our discussion of the aquarium plumbing. All plumbing is directed by the pump as the water level of the tank fills, it will overflow into, you guessed it, your overflow box. The water will slowly drain through the overflow box through whatever system you have (Herbie, Bean Animal, etc.) and flow back into your sump, and if you have one, your protein skimmer. As the amount of water in the sump increases, the pump will send it up the return line towards your reef tank again, where the process repeats itself.

In between each of the plumbing destinations, there are drains, pipes, bulkheads, and hoses that help the water get where it needs to go inside your system. Understanding the best way to utilize these pieces will ensure that your plumbing system will not only keep your aquarium running but also allow any future maintenance to be a sinch. For instance, make sure to use union fittings on the PVC pipe that attaches to the pump The union fittings are much easier to take apart and will allow much easier access to the equipment down the road.

A quick word on sump size. Your sump is designed to hold water for your plumbing but it also can hold a lot of other things if you are willing to utilize it as such. Think about whether you would like to use your sump for anything besides your pump. The sump setup can be improved by including a skimmer or even a refugium for macroalgae and these equipment upgrades can help you significantly, even if you aren’t ready to include them in your tank quite yet.

Factors to Consider when Choosing a Return Pump

Pump Flow (gph)

This obviously varies from pump-to-pump but is stated by the manufacturer and is easy to find. Don’t confuse this with the flow it’ll pump into your aquarium though. You need to consider losses from plumbing and how high the pump needs to pump up the water from your sump.

Pump Head Pressure (feet)

Also varies from pump-to-pump and is also stated by the manufacturer. This isn’t a single number but a range and is often represented by a graph. There is a maximum amount of head pressure that any return pump can overcome. Not only that but as head pressure increases, gallons per hour decreases. You need to determine the amount of head pressure loss due to your return plumbing and compare it to the manufacturer’s information and ensure that it is still going to flow enough water to meet the requirements of your setup.

Plumbing Head Pressure Loss (feet)

The distance your plumbing runs, the distance from your sump water level to your main display tank’s water level, and the complexity of your plumbing all add to the head pressure your return pump must overcome.

Overflow Flow (gph)

Overflows are gravity-fed. As your return pump pumps water into your main tank it will fill up and the water will literally overflow into your “overflow” and down into your sump. The overflow must be able to flow more gallons per hour than the pump is flowing gallons per hour into the main tank.

Saltwater FOWLR & Reef Tank Turnover Rate Calculator

When calculating turnover you need to account for the amount of water in your main display tank as well as the water volume in your sump. You don’t have to be scientifically accurate about this. A reasonably close number for the total water volume in your system is good enough.

The recommended turnover rate is usually between 5 times and 10 times for a reef tank and 10 times to 20 times for a FOWLR aquarium. What this means is that the entire water volume of your display tank and sump should be pumped through your return pump 5 to 10 times per hour for a reef tank and 10 to 20 times per hour for a fish only with live rock tank.

While most people generally consider higher turnover rates better, there are some that believe lower is better. In general, the argument for a lower turnover rate is prolonged exposure of the water to the equipment in the sump such as a protein skimmer or heater, as well as longer exposure to refugium macroalgae (if you have a refugium) and any filter media you may have in your sump.

I’m in the high-flow camp but I’m open-minded. If I hear compelling reasons to lower my turnover rate I’m fine with considering it. My advice for now is 10x turnover for reef aquariums and 20x turnover for FOWLR tanks.

If you don’t happen to know the volume of your aquarium or sump you can use our aquarium volume calculator to figure it out by plugging in the dimensions.

Aquarium Return Pump Calculator

The pump is incredibly important to keep the movement throughout your plumbing and overflow. However, the flow rate of your tank can only be as the size of your pipes which can only move water as large as your drains are. You can’t make the overflow move water just by having a pump working harder.

There is a limit but you can find the sweet spot for your tank by using the calculator below to help determine what you will need for your flow rate. The rate is calculated in gallons per hour (gph) to see how many gph are passed through your tank.

To determine what return pump you need for your aquarium you need to calculate the the head pressure loss 

The gph will have a direct relationship with the size of drains that you will need to have drilled to have an effective drain as well as the size of your overflow box. For instance, 1-inch bulkheads will work well with up to 150/gph and 2 inches of linear overflow space.

NOTE: This calculator assumes the inner diameter of the plumbing is the same as the outlet size of the pump you will select.

Now that you know the head loss of the plumbing that will be attached to your pump you can refer to the manufacturer’s chart for head pressure loss and see if the pump you’re considering is capable of flowing enough water per hour to meet your turnover needs.

Overflow Size Calculator

If I’m honest, there isn’t a strong need for an overflow calculator most of the time. You can simply plumb in a pipe to your sump that is quite large and more than capable of flowing enough water beyond what your return pump can push up to your main display tank.

Where an overflow calculator can come in handy is when you’re trying to create a quiet overflow and want to tune it to not gurgle. Having a better understanding of how much water the pipes will flow can help you better design a quiet overflow.

For instance, the BeanAnimal overflow design requires one pipe that runs at a full siphon. Another pipe is designed to only have just enough water flowing through it that it will cling to the walls of the pipe and not have enough water flowing through to create any gurgling. There’s a third pipe in the design that is for emergencies. In the event that one or both of the other pipes become clogged or something.

Even with the BeanAnimal design overflow, you can install very oversized pipes and add a valve to adjust the flow. You do want to ensure that your emergency pipe can handle all of the flow your pump can throw at it and then some to be safe. The problem comes in with knowing how large of a pipe is overkill or not.

Calculations in fluid dynamics are complex, to say the least, and over my head. Fortunately, forum user BeanAnimal himself answered a question in a post by forum user “scolley” which lays out the formulas for how to calculate flow through overflow pipes. While I don’t claim to have a grasp of how these formulas work, I did put together a calculator below based on them so you can get a reasonable idea of the flow of different-sized overflow pipes. One note, the calculator is assuming the pipes are essentially a straight shot from the overflow down to the sump so there is no accounting for plumbing restriction.

Schedule 40 PVC Diameters

Pipe SizeOuter Diameter (inches)Inner Diameter (inches)
1 1/4"1.6601.360
1 1/2"1.9001.590
2 1/2"2.8752.445
3 1/2"4.0003.521

Schedule 80 PVC Diameters

Pipe SizeOuter Diameter (inches)Inner Diameter (inches)
1 1/4"1.6601.255
1 1/2"1.9001.476
2 1/2"2.8752.290
3 1/2"4.0003.326

How to plumb and install a return line from a sump to display tank

How you choose to design your plumbing will depend on your own preferences and particular setup. The first thing you will need to decide is what type of materials and the size of those materials will you need to complete the plumbing for your tank.

Most people opt to use PVC pipe since it is easy to find, easy to work with, and, best of all, cheap. We are going to use PVC but note that while some piping might have an outer diameter that meets your needs, they can have a much smaller inner diameter which can restrict flow. Double-check the materials that you’re working with to ensure that you are getting exactly what you need for your reef tank.

All a return line is is piping that extends from your pump to your display tank. It isn’t nearly as complete as your overflow box design can potentially be but you still need to be cognizant of your design choices. The main thing to keep in mind here is that the pump can’t stay where it is forever; it will need to be removed, cleaned, and reinstalled regularly so it is best to design your return line for that process to be as painless as possible.

To achieve this, use a union piece connecting your return pump to your line. After this, it is fairly simple to pipe your line up towards your tank with 2 street 90-degree PVC pipes forming a u-shape and allowing the water to flow directly into the reef tank. The u-shape piping should rest on your tank’s rim for better security. However, now that you have your line partially set up, you need to secure it in place. This step is extremely important as water will be flowing constantly through these pipes and if a dog, child, or even you knock the line loose, it will be one big cleanup job. You can opt to use zip ties to keep it in place but they might limit the area in which you can secure it. They also have PVC mounting brackets which can come in handy for larger objects that you can’t get a zip tie around.

In the short term, you could leave your return line like this but it will likely cause some unwanted noise to come from your tank as the water splashes its way in. For a more optimal return, we need to attach a bulkhead to the outlet of your return line, which we will use to install a loc socket for a more discreet return to your tank.

What is a reef tank plumbing check valve?

Potentially one of the most devastating things that can happen with your reef tank is a flood. Not only will it create issues with your display tank but it will destroy your home, office, or other space where the rank is set up. That is why it is important to take care when building your overflow box, sump, and other piping essentials to ensure that your tank can handle catastrophe.

One of the ways that people try to ensure a little more security in the tank is to use a piece of plumbing equipment called a check valve. The check valve is designed to stop the water flow in return lines in case of a power failure so the sump doesn’t overflow. However, the valves can often be more trouble than they are worth since well-designed aquarium plumbing will be able to handle the water draining back into the sump. Check valves have the potential to fail when they are needed due to blockages preventing them from closing. Anything from algae to creatures can prevent the mechanism from operating as intended. In that case, it acts as more of a false sense of security than something that will save you in an emergency.

A benefit is that the check valves are often made of a clear material which allows you to more easily see the inner workings of the device. However, that also allows light to get inside and as we know algae love light and water. Your valve will have both, so if you decide that it is a path that you would like to explore, make sure that you are cleaning the valve regularly.

The number one thing is to design your plumbing to be able to handle adverse circumstances, whether that be a change in water flow or a power outage. The major factor that you should consider is the size of your sump. If the water line is already high in your sump with the pump running it might not be big enough. Remember that the sump will be where all the water in the plumbing line returns to so if it is large enough to support that increase in water, then you won’t have to deal with flooding in your home.

Check Valve

Check Valve

Single Speed
Return Pump

Adjustable DC
Return Pump

Overflow design

The choice in overflow can also affect how you might want to set up your aquarium’s plumbing. The Herbie method of overflow makes a siphon but that can only be fully utilized if the sump is directly below the overflow box. Horizontal pipes or tubing are not ideal for plumbing since once it’s in the overflow box, designs often use gravity to make the siphon work effectively. If you think of the equipment that is beginning to mount up, a lot of space is being utilized in the same area. Just something to keep in mind as we move further into the discussion of plumbing.

Aquarium Overflow Types

If you’d like to learn more about these 3 overflow designs, I recommend reading our in-depth articles on the Durso, Herbie, and Bean Animal overflows. (Durso article coming soon!)

What is a reef tank return nozzle?

A return nozzle is a piece of equipment that connects to the elbow PVC pipe that leads back into your display tank. It is meant to allow the flow to be more controlled in its arrival so there is less splashing. The nozzle is often partially submerged to allow for quieter return lines as well. There are different variations of return lines that allow for more control in how the hose is positioned and thus directs the water flow upon return to the display tank.

What is a ball and socket loc-line?

A Loc-Line is like a flexible hose that is used to get more variation in nozzles on return lines. There are also different types of Loc-Line nozzles that allow you to have more varied water flow into your tank. There is a level of customization and control that you get when using a loc-line that you simply don’t get when simply using a PVC pipe for your tank’s plumbing. A must-have for aquarists who would like a more flexible option for their pumps.





Best aquarium plumbing return nozzle

The best return nozzle will be one that gives the speed or variation that you need to the water flow as it returns inside the tank. The best nozzle for your outlet may look different than the best nozzle for another overflow system. Think about how you would like to manipulate the flow within your tank. Do you need it to be fast? Or maybe you wish that you didn’t need to install that second powerhead? Your decision here can help to reduce additional purchases.

  • Oscillating nozzle – Oscillating return nozzles or random flow nozzles are usually 3D printed loc-line nozzles that give a varied flow to your tank every time. They can do this because inside the nozzle there are little fins that help to steer the flow nozzle wherever the water goes.
  • Flare nozzle – There is also the flare nozzle that allows for a wider and evenly dispersed return flow through your reef aquarium. It isn’t random like the oscillating return nozzle but will offer little to no variation to the flor from your return pump.
  • DIY nozzle – You could also try making your own return nozzle for your return plumbing. The first thing your need to do is make sure that you are making a nozzle that is smaller than the drain. You can use simple PVC fittings to complete the outlet. But if you want something cheap, you can use a little bit of tubing to accelerate your water flow.
No matter which nozzle you decide you want to use, using loc-line for the end of your return line is the best choice. Loc-line will give you a huge amount of control over the direction of your return nozzle and allow you to adjust it to help eliminate dead spots or prevent excess flow from blowing sand away from spots on the bottom of your tank.

Final thoughts

Now you have the basics of how to arrange the plumbing in your tank. However, this is only half the equation. If you would like to read more about how to design your overflow box, check out the Bean Animal article and Herbie article on here Reef tank Resource!

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