Herbie Overflow Method (DIY Plumbing & Silencing Guide)

Image Credit: 915Mang Via YouTube
Image Credit: 915Mang Via YouTube

Herbie Overflow Method (DIY Plumbing & Silencing Guide)


Plumbing is one of the most important and often not thought about design factors to a reef aquarium. It is important to choose a plumbing method that you are comfortable implementing into your aquarium. You will want to take into account factors like noise level, emergency scenarios, and available space in order to choose your method of plumbing.

In this guide, we will show you how to set up a near-silent Herbie overflow system for your reef aquarium, and we will explain how it stacks up against other common aquarium methods of plumbing.

What is a Herbie overflow?

Put simply; the Herbie overflow is made up of 2 standpipes. One of the standpipes is the main drain to the tank, while the other is an emergency drain. The design is a great way to ensure that your tank won’t overflow while running quietly; this design was popularized by a forum poster who mentioned his setup. People loved the design, and eventually, the name of the forum member became the name of the overflow design. It almost makes you want to popularize your own design in the hobby just to have your name branded in history.

One of the biggest draws to this design of overflow is that the Herbie style can run near-silent, unlike the Durso. The reason is that the Durso only has one pipe, which allows both water and air to force their way through, causing the obnoxious gurgling sound. Herbie overflow avoids that problem by using a siphon to help drain the main standpipe. The full siphon is created by restricting the flow of the main drain. The water then works with gravity to drain into the sump, where it will eventually return back to the tank.

If the main drain pipe becomes clogged or restricted for some reason, there is still an emergency drain pipe available. The emergency drain sits at a higher level which means it won’t be used unless there is an issue with the main drain. It also isn’t a siphon, so when it becomes active, you will be able to hear that there is an issue with the main drain, but that doesn’t mean the emergency drain pipe doesn’t pull its weight. It will assist the main drain in making the plumbing of your tank quieter.

How does an overflow box work?

An overflow box is designed to catch the displaced water from your aquarium as water comes back from the sump. The overflow essentially is a holding pin until the displaced water can go through the rest of your plumbing and be returned to the tank. However, in order to get it out of the overflow box, you need to set up some sort of overflow drain to actually drain the water from the box. There are three common overflow designs that aquarists use for their tanks.

  • Durso – The Durso system uses a single elbow drainpipe to control the flow in the overflow box. This system does not utilize an emergency drainpipe.
  • Herbie – Herbie will use two standpipes to more safely control the rate of flow from the display tank. One is the main standpipe, while the other is an emergency.
  • Bean Animal – Bean Animal is a combination of the plumbing methods listed above. It uses the main siphon standpipe method from Herbie with an emergency drain that sticks out of the water. It also has a Durso-style 90-degree pipe that sits near the crest of the top of the water.
Aquarium Overflow Types

Gate valve, main drain, and emergency drain relationship

The flow in the main drain pipe will determine how quietly your drain can operate, and your choice in the valve will determine how easily you can make the adjustments. The goal is to match the return pump and its rate with the rate of the drainpipe while making the water drain as quietly as possible. The adjustments are best made with a gate valve as compared to a ball valve.

A gate valve allows for much more precise adjustments, but with some additional trial and error, you can make a ball valve work; it just might not be as precise as you might like for your tank. Once the flow is where it should be, you make the final adjustments to the rate until the water level is just barely trickling into the emergency drain. This will help to guarantee that your overflow box is running as quietly as it can.

Of course, you can always just run the Herbie overflow normally without using the drainpipe to quiet your system. The only drawback is that you might have a louder overflow box, but it will be a safer overflow box that is less prone to flooding.

Types of overflow boxes

There are actually different kinds of overflow boxes, and the design you choose will determine how you can move forward with your plumbing.

  • Internal overflow box – These boxes will require that you drill holes into your tank and install your own piping to a design that fits your desires. However, if you are able to make the necessary cuts, the inter overflow box will be very helpful and flexible to your plumbing needs. As the name suggests, this design fits inside the tank.
  • External overflow box – These boxes won’t require that you drill holes into your tank, but you will also have less flexibility with your final design as a result. The external overflow box isn’t recommended if you are able to install an internal overflow box because it has the potential to overflow with no ability to make a fail-safe drain.

Keep in mind that the size of your box will determine the design for your overflow system. In many cases, you will be able to tell whether the box you buy will be able to fit the overflow system design you are trying got implement. How many pipes can the box hold? If you are aiming for a Herbie style overflow system, then you need to able to fit two standpipes.

DIY Herbie overflow

Now that you know the general principles of the Herbie style design, actually building it should be a straightforward process.

Materials needed

  • Overflow box
  • Silicone
  • Corded electric drill
  • Hole saw bit
  • Drill guide (preferable)
  • Safety glasses/ gloves
  • Masking tape
  • Bulkheads
  • PVC pipes
  • Valve gate (preferably) but a ball valve will also work
  • Strainer (this will help to prevent any future clogged pipes)

Step by step process to build Herbie overflow

Creating your own Herbie style overflow is a fairly easy process (for a plumbing project).

  1. The first thing you want to consider when setting up your overflow box is where your sump is located. Ideally, you will place your sump directly behind your aquarium, right below where you plan to install your overflow box. Why is this a good idea? Because we are using gravity to move the water for the most part. By placing the sump directly under the overflow box, you are ensuring that you don’t need to create any horizontal changes in the flow, which could slow down the rate of the overflow for your reef tank.
  2. Now that your sump is in place, you can install the overflow box above it. Since we are using an internal overflow box, we are going to need to cut two holes into the display tank. To do this, take your reef tank somewhere where glass clean-up will be easy. You might even consider putting towels down to better catch any small particles of glass that may fly out from the drill. Next, mark the areas of the reef aquarium you are trying to cut, so it is easier to match up. Remember that we are trying to build a Herbie-style overflow system, so we need to have one hole higher than the other. The higher hole will be where the emergency drain is installed. Place masking tape on the inside of the tank to help catch the glass and disc that will be cut out of the tank. Each hole should be high enough that when the overflow box is installed, the waterline will just barely be reaching the top of it.
  3. Begin running water over the tank and begin to line up your drill with the guide if you have one available. Start the drill and very slowly guide it towards your hole outline. To cut through the tank’s glass, it will take the drill a couple of minutes. Don’t try to rush it and push down on the drill because you are more likely to damage the reef tank in that way.
  4. Honestly, that was probably the hardest part, and now that you did it, you are mostly in the clear. Prepare your tank inside and grab your overflow box and silicone. You are going to line the rim of the box that will be touching the glass with the silicone. Now wipe the silicone that might have moved to the outer rim. Running your finger along this will help to create an air-tight seal and secure your overflow box to your tank. wait 24 hours and then fill it with some water from a pitcher just to see if it is truly sealed. You can also install a box on the outside, but the box will need to be fitted with additional holes to allow for the two standpipes.
  5. Next, we have to install our bulkheads to the drilled holes in the tank. The bulkheads will allow water to transfer effectively into the overflow box or into your standpipes.
  6. Whether you have chosen to have your Herbie style overflow system begins inside your tank or outside, the most important thing is how we are installing the standpipes, which will drain the water from the overflow box and transfer it to your sump system. If you are using an external method, you will need additional bulkheads where the standpipes meet the overflow box.
  7. Your main standpipe should be set at about half the level of the desired water height in your overflow box. Place a strainer on the top of it to help prevent a clog within the overflow system. Right after the bulkhead, install more piping and a gate valve (or ball valve). Install the rest of the main drain pipe that will lead to your sump system.
  8. The emergency drain pipe should be set near the very top of the desired water level. In fact, once there is water, there should only be a small trickle of water that is ever entering the emergency drain pipe at any one time. This is how you create a Herbie-style overflow system that can run nearly silent. Finish installing piping that leads to the sump system for your emergency drain. Remember that this drain does not receive a gate valve or a ball valve.
    • The drains that are leading to the sump should be submerged by about an inch of water.
  9. Time for a test run. Begin running your tank’s water and watch as the overflow box begins to fill. You will want to adjust the gate valve to set the water height within the box. If the box is filling too slowly or quickly for your needs, you will need to make adjustments to the return pump rate. The ideal Herbie method is to match the return pump with the drain’s rate of flow.
    • The goal is to use the valve on your main pipe to create a full siphon that lets water in and next to no air. Air does not need to be run through the sump, so it has no business taking up valuable space.

Herbie overflow flow rate

The flow rate of your Herbie overflow should match the rate of your return pump, so you have a consistent water line in your box. You can adjust the main gate valve on your standpipe to try to match this level and keep it resting right at the height of the emergency drain pipe.

How to convert Durso to a Herbie overflow

If you currently have a Durso overflow system, but you want to convert it to the Herbie method, then you are first going to want to take stock of the available room that you are working in. As you know, Herbie style requires extra area for the emergency drain, so if your overflow box doesn’t have sufficient space for a second pipe, then you will need to almost completely start over with a new box.

If you have the necessary room, then you have much less work ahead of you. The first thing you will need to do is remove the Durso standpipe, as you will need a different design of standpipe for your Herbie overflow. Luckily, from the bulkhead down, you can keep everything in place (given there is sufficient available area for another bulkhead to be installed). Cut a hole in the overflow box and install a second bulkhead where the second standpipe will go.

Install PVC piping into your sump, and remember to have it submerged about an inch into the water of the sump. Now you just need to install your main standpipe at about half the water level of the box and your emergency drain pipe. Don’t forget to install the strainer on the main standpipe!

The emergency pipe should be set right at the crest of the water level so the water can just trickle into the drain. Your emergency standpipe should not be completely submerged. Not only will this not be a silent method and create a lot of noise, but it will also defeat the entire purpose of the fail-safe design. Congrats, you just turned your Duros into a Herbie!

Herbie vs. Bean Animal overflow

The complexity doesn’t end at the Herbie overflow. There is another plumbing design called the Bean Animal, and it uses three standpipes in its design. Think of the Bean Animal as a combination of the Durso and Herbie designs as it uses both methods. One standpipe is open, similar to the Herbie, and is placed at the middle of the water level. A second standpipe, called the secondary drain, is placed higher in the water level and is the same pipe design as Durso. Finally, there is the emergency drain pipe which is placed outside the water, unlike the Herbie, which uses its drainpipe to help with the noise levels. The emergency pipe will only be used in this design during emergencies. The Durso standpipe will assist the Herbie-style drainpipe.

So what does this do? The Bean Animal’s complicated design ensures not only safety with its three standpipes, but it will run completely silent with little adjustment. The problem with the bean Animal is that it will take up a lot more area and will require more work on your part initially. However, if you are looking for a completely safe option for our reef aquarium that will be silent, then the Bean Animal might be your best option. However, the Herbie is functional, and many people don’t believe the added security of the Bean Animal is necessary. Hence, it is up to you what you would prefer for your aquarium.

Final warnings on design

You might have the best-designed reef tank in your state, but that doesn’t make you immune to some of the issues that can arise. Even the best of us have power outages and clogs in our tank, so it is best to understand what happens during these situations.

Power outage

In all likelihood, if a power outage were to occur, your sump will cease to pump water back into the tank. What this means is that your overflow will continue to send water into the sump since it is driven by gravity. You need to make sure that your sump can hold all the water that might drain from the display tank. The draining will stop when the water line is below the strainer on the main standpipe.


Clogging in your reef aquarium plumbing can happen, even with the Herbie style plumbing. Sometimes your strainer will pop off, or debris will accumulate, but thankfully your drainpipe will be there to keep up with the water flow until you are able to remedy the issue. If aquarium plumbing gets clogged, it can be completely okay as long as you are prepared for the scenario.

Final thoughts

Hopefully, now you have a great understanding of how to set up a Herbie-style overflow system in your own aquarium. it might seem intimidating when you break out the power tools, but it is a very straightforward process, so just take it slow and be careful. Once you have your reef aquarium plumbing set up, your display aquarium will be working great. if at any point you decide to change your design for a different one, make sure you are taking the proper precautions to protect your fish and yourself as your work.

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