Herbie Overflow Method Reef Tank Plumbing Guide

The Herbie Overflow Method is a simple, proven plumbing setup that’s been around for many years. At it’s most basic, it consists of 2 standpipes in an overflow; a main drain regulated by a valve that runs as a siphon, and a separate unrestricted “emergency standpipe”.

The setup enables you to:

  1. Run a completely silent drain from the overflow to the sump below
  2. Have it be completely fail-safe from possible flooding with proper design and maintenance.

It is the simplest plumbing method that accomplishes both of these things.Herbie Overflow Diagram

History

The method was popularized by a Reefcentral.com thread started by a forum member “Herbie” around 2004. As people started using the method on their tanks, many forum threads started and there are literally hundreds of posts out there about it. The difficulty lies not in the method itself, but in sifting through all those bits and pieces of info just to figure it out.

About this guide and a heads up

This guide explains the regular operation, each component of the design, and gives tips along the way. For the sake of simplicity, all of the content and diagrams describe the most simple and conventional Herbie setup, — an overflow box with standpipes coming in through the bottom. In some cases the pipes will have to pass through the side of the tank, but the mechanics of everything will be the same.

You should be aware that:

  • It is not completely a “set-it-and-forget-it” method… It needs to be regularly inspected and properly maintained. See Best Practices
  • There are all kinds of people out there who run the system in one form or another, and they all have a slightly different opinion on how they think things should be done. I am only one of these people. the most important thing is to understand your own setup. You can choose to do things differently with certain parts of the design, but try to be aware of any risks you may be opening yourself up to when you do so.
  • There is another similar method called the “Beananimal” drain (also named for it’s creator) which is slightly more complicated in design and uses 3 standpipes vs. only 2. It’s generally only used on custom tanks over 150 gallons because of it’s larger physical footprint and more intricate setup work involved compared to the Herbie. This guide won’t attempt to debate the pros and cons of both methods, although the Beananimal system does have the advantage of the extra “dry emergency” drain which provides another redundant safety measure.

The Siphon that makes the Herbie work

Any time you have air and water flowing through the same drain, you’ll get noise. This is the main shortfall of single-pipe-drain methods like the Durso and it’s siblings. A siphon drain has much more flow capacity because air never runs through the pipes once it gets going.

The way the siphon on the Herbie is achieved is by manually constricting flow on the shorter main drain with a finely-adjustable valve. Once the air is purged from the line and the siphon is fully engaged, it continues to run this way 24 hours per day until something interrupts flow like the return pump being shut off.

Adjustment of the Valve

valve aquarium

To begin, the valve is opened all the way — then slowly closed off until the siphon is achieved. Fine adjustments are then made until the flow of the siphon closely matches the amount of water being returned to the tank, which will stabilize the water level in the overflow. Although possible, perfectly balancing the water level until it remains totally still inside the overflow is both difficult and unnecessary (mostly just annoying). Even if you do manage to get it stable, slight variations in the system such as changes in resistance of water through the plumbing will inherently change the rate of flow over hours or days. For example, the growth of slime in the pipes.

herbie overflow animation

What happens when a siphon valve is adjusted. In real time the water would take up to a full minute to reach the E-drain

Simply by allowing a very slight trickle of water to enter through the emergency standpipe at all times, the system does not require perfect adjustment and the siphon will re-start on it’s own more easily (such as after an interruption in the return pump’s operation). We are talking a trickle here — just enough to negate the need for constant fiddling, but still allowing the emergency drain ample capacity if needed.

To accomplish this, you simply stabilize the water level as best you can inside the overflow, then close off the valve’s flow a very tiny amount past that point. This causes the water level inside the overflow to rise, very slowly, and come to rest at the level of the emergency standpipe — where the trickle of water will begin flowing down it. This adjustment should be as small as possible because ideally you want the trickle as small as possible.

A slight trickle of water flowing down the emergency pipe has a few effects on the system including:

  • The operating water level remains up at the top of the overflow box. Water passing over the the weir falls only a short distance, so it won’t splash and create noise.
  • The volume of water in the overflow is always consistent. The return pump chamber in the sump becomes the only place in the system where the water level can fluctuate.
  • A trickle of water breaks the surface of water inside the overflow, preventing any scum from accumulating.
  • The need for constant adjustments is eliminated.

Let’s Pause Here… For the sake of discussion, I’ll mention a debate that currently takes place. It regards running an Emergency drain with the “Trickle” method. There are some people who think that running a dry pipe that never touches water is the only way it should be done.

I have the opinion that running a “Trickle” down the Emergency drain is a safe method. This is only the case if you safeguard your valve and maintain the overflow. I wanted this guide to be just about explaining the basics vs. debating different opinions, so that subject is in a separate post here Herbie Overflow Emergency Line – Running Wet vs. Dry

Moving on…

System Design

External Overflow with Herbie Setup

Valve Selection

Due to the need for fine levels of adjustment, installing a quality valve is suggested.

Gate Valve

This valve allows precise adjustments to be made with a minimum effort. The “Spears” gate valve (shown) can be taken apart and is regarded as the best available option.

Gate Valve Herbie

Spears Gate Valve

Ball Valve

The higher quality ones have a smooth opening/closing action, and built in unions which are an advantage. A “Single Union Ball Valve” or “True Union Ball Valve” are the only ones that should be used. They are cheaper and easier to find than gate valves. The common “Straight Ball Valve” should be avoided.

True Union Ball Valve Herbie

True Union Ball Valve

Even a quality valve will tend to start to get sticky and eventually seize up after months or years in a high-calcium saltwater tank. To remedy this it’s a good practice to detach your valve and get rid of any deposits. Soaking the valve in vinegar works well.

Thinking Ahead – If the valve doesn’t have a union built in — one should be installed close to it between the valve and the bulkhead so you can easily detach your hoses and get to the valve assembly with relative ease.

Main Siphon Standpipe Height

This can potentially trip you up if you haven’t set up the method before. The main valve standpipe will work at almost any height you make it as long as its lower than the emergency standpipe. However this is true only to an extent (see below).

Herbie Overflow Standpipes

Help the Siphon get going on it’s own — by having the height of your main valve standpipe about 6″ deeper than the operating water level of the overflow, usually the height of the emergency standpipe.

6″ is a general rule — it depends on the diameter of pipe of the siphon inlet. This is also a guide based on an overflow that is at least 8″ high. The height of the siphon inlet in the overflow is something you may want to experiment with in your own tank while in the testing phase.

A sufficient volume of water above the siphon standpipe prevents air from sucking in from a vortex: where a water funnel is created and air sucks down creating a slurping noise. This will make the line go back to silent operation faster. This is why you see some overflows (namely the bean system) using a downturned elbow to locate the inlet deeper in the overflow box.

A larger diameter pipe is less susceptible to the vortex-effect of air sucking down from the surface than a small diameter pipe with the same flow rate.

If you forgo the raised main standpipe (such as on the right of pic above) it will take the guess work out of it, just be warned that ALL the water in the overflow will drain into the sump when you shut off your return pump. Any livestock in there will be left high & dry.

Emergency Drain Setup

herbie drain emergency height
This drain is what makes the system fail-safe in the event of the main valve standpipe getting clogged. It should be designed simply as a straight (as possible) unrestricted pipe going down into the sump and into the water, never joined with other pipes.

You want the emergency to have max capacity, so most people leave it open and don’t use a strainer on this pipe.

Don’t install a valve on the emergency pipe — just don’t…no good can come of it.

Emergency Drain Standpipe Height

As a measure to prevent noise from falling water in the overflow, the emergency standpipe inlet should only be around 1/2″ – 1″ below the height of the overflow weir.

Starting and Stopping

When the return pump switches on, and water starts passing through the overflow, the siphon should engage and go back to normal operation completely on it’s own. While this is happening, you may observe a temporary increase in water going down the emergency standpipe. This should only go on for a minute or so until all the air inside the main valve standpipe exits down through the end that’s down in the sump. The siphon will then go back to taking the full capacity you adjusted it for.

Under the tank

Drain line Outlets in the Sump Below

Both drain outlets should run down from the overflow into the sump below. The siphon drain must have it’s outlet submerged, but by no more than 1-2 inches. Any deeper, and air can’t purge from the line as easily when the siphon is starting. It is also preferable to locate this in a sump chamber with a constant water level.

For the emergency line, submerged depth of the pipe doesn’t matter — but most people also have it exit underwater to limit noise and splashing from running a trickle.

While not as important for the emergency drain, the main siphon drain should be run straight as reasonably possible downwards into the sump, as any horizontal runs will make it more difficult for all the air inside the line to exit the pipe down in the sump or even trap air in some cases.

It is also important to note that you should not attempt to Tee off either drain, as it will most likely interfere with the siphon operation, capacity of the emergency drain or cause other problems.
One does not simply Tee off a Herbie Drain

Sump Capacity

When the return pump is shut off, the water inside the overflow will drain and come to rest at the level of the main valve standpipe. Depending on how much water volume this is, it will drain to the sump all at once – so make sure it can accommodate the extra water.

1380510475_protect

Best Practices for a Problem-Free Overflow Box

Doing these things will make the main siphon less likely to clog.

Use a Strainer

reef-overflow-strainers-gmacreef

Install a Strainer on the Main Valve Standpipe. This will keep any debris, small snails or algae clumps from interfering with the valve and choking off the drain. There are different strainers out there, and one with smaller holes will protect better, but clog with junk faster. Try to get in the habit of inspecting the strainer when you observe and check on your tank. After all, you want it to prevent clogs, not be the source of one.

You might be thinking, “I don’t need no stupid strainer” — YES YOU DO!

Listen up.

With the nature of a siphon, water moves very quickly through the valve opening. Most times you’ll find that the valve needs to be closed-off in excess of 50% shut to achieve balance from the return. A mostly closed-off valve opening is very small during operation. This makes it more susceptible to obstruction by an object.

Having a strainer in place is the last line of defense before your main drain clogs.

Quick tip – keep more than one strainer (they are cheap): If you have a clean one ready, you can easily swap out the old one without having to shut anything down. This also makes it less likely you’ll forget to put it back on.

Cover Your Overflow Box

A covered overflow will prevent livestock in the tank from jumping or crawling inside. This is a good idea to further protect the valve against clogs, and can also help to limit algae growth. You’ll also save yourself having to catch a stray fish inside the overflow which is a real pain. A simple piece of acrylic cut to size does the job.

Visual Inspection of the System

You might want to place your overflow in such a way that you can easily look into the box. You want to know:

  1. Is the water level where it should be?
  2. What is the condition of the strainer? Does it need cleaned?
  3. Is there any debris or livestock in the box?

Other Considerations in your System

Is my tank the right size for this method?

Drilling and mounting bulkheads to a tank adds lateral weight and forces on the glass. This limits what size aquariums are suitable for the method. Glass with thickness of at least ¼” can withstand these forces, and generally found on tanks 40 gallons and up.

Don’t waste your time or risk having a future catastrophe later on by drilling a tank that is too small for the method. As always, check to make sure the glass you are drilling is not tempered. There are many videos on drilling glass on YouTube and it’s easy to do with diamond hole saw bit.

Size of plumbing

There is a general consensus that the Herbie method should never use less than 1″ pipe for plumbing, no matter what size tank. You want to be 100% sure that your single emergency drain is completely capable of handling all the flow that the return pump can throw at it in the unlikely event of total clogging of the main drain.

If your tank came pre-drilled with 2 holes in the overflow as in a lot of older “reef-ready” tanks, use the one with a larger diameter (usually 1″) for your emergency and the smaller diameter one for the main siphon drain. Keep in mind that your flow will be drastically reduced on smaller size pipe.

For systems where return pump flow is up to around 330** gallons an hour, running a 1″ emergency line will be sufficient. For tanks above about 90 gallons you may want to bump-up your plumbing size to 1.5” or 2” in diameter. These can handle way more flow.

**While a full siphon in a 1″ pipe can move over 1500 GPH, a single 1″ line that is simply draining (in that siphon action has not yet engaged) can safely handle around 330 GPH. This is a low estimate, but There is more to the discussion of plumbing size that is not in the scope of this guide. Bigger is better with plumbing size. Here is a link about pipe diameters and flow. The Flowrates through various Bulkheads (In relation to overflow drains)

The trend in the last few years is to use efficient powerheads to create high flow in the tank, while running a moderate amount of flow through the sump. This means you can run a smaller, quieter return pump and not push the capabilities of your overflow design as much which is a smart strategy.

Return pump plumbing

The return pump also plays a part in the operation of the overflow and in short, simple is better.

The system will work best if the return rate is kept as consistent as possible, and not allowed to fluctuate from day-to-day.

A common practice is to to Tee off the line above the pump outlet to feed a Refugium, Skimmer, or run media reactors. This can be less than ideal with a siphon-based overflow method. For example, if the return pump is Tee’d off and also feeding a media reactor in the sump, then variations in water flow will start to happen. Water resistance inside the reactor will slowly change as the media becomes depleted or dirty. This in turn changes the rate of flow pushed up to the display, and at the overflow as well.

To avoid this constant readjustment, the return pump’s only job should be pushing water up to the display tank. Not to say you can’t do it, just understand any variations you add into the plumbing of the return line can have effects down the line.

More info about return pumps in this article here: What return pump should I choose for my reef tank?

Assembly and Gluing

Your plumbing fittings inside the overflow can generally be fit &threaded together and don’t need to be glued as there is no risk of leaking. This will also allow you to make changes as you initially test out the system by trying various pipe lengths. On the exterior of the tank, fittings and pipe should absolutely be glued with PVC primer and glue (available at any hardware store). Installing unions between the outside of the bulkheads and the plumbing lines/valve is a good idea and allows for the hoses to be removed for cleaning or if you have to move the tank.

More info about how to glue and connect the various pieces: Plumbing Assembly for your Reef tank

Testing the system

There are a few initial tests you should do with the system to ensure problem free operation for years to come. Any problems are better to find out in the garage than in the living room. As long as it passes these tests then you are ready to go.

  • Test your emergency drain’s capacity by closing off the siphon valve completely. You must confirm it can handle what your return pump is pumping up to the tank with ease. If using a controllable DC pump, make sure the drain can handle flow at 100 percent power.
  • Ensure you have the right sump capacity by turning off the return pump, then watch both the drain and return lines empty into the sump. Make sure it can handle the extra water (also watch your skimmer).

One Final Note

Ultimately you are responsible for your own tank and your own property — there is the potential for water damage that comes from owning any aquarium. As I have said earlier, the most important thing is to understand how your own system is set up. Learn as much as you can and don’t cut corners. Enjoy your quiet tank!

About this Page

While my original post was written in June 2012, it has grown into a full guide. I have made several edits to clarify some of the concepts and added a few sections based on some if the comments left below and various forum threads linking here. Thanks to those who have participated in the discussion. Ask me a Question using the Contact Form or write it in the comments below.

  • Not_Bob

    Thanks for this site. The one question I have after reading any sites about the Herbie overflow relates to the emergency drain. Most sites show the emergengy drain as being an inverted U and say to run the drain below the water surface of the sump. Will that work if there is no air hole in the U?

    • http://gmacreef.com gmacreef

      I have seen the added elbows to form the downward U on the emergency drain on a few diagrams and pictures such as you described. From what I can gather it is a modification that is done to minimize noise. There can sometimes be a hollow sound echoing through the emergency drain – however in my experience this just means that the valve on the main drain isn’t adjusted correctly (too little flow) and is allowing too much water to pass through the emergency drain. It is normal for this to happen as the siphon gets going again (such as after you turn your return pump back on) You want just a trickle of water going though it which won’t make any noise. I don’t see a need for it, and it has the potential of being something that a snail could climb into and you wouldn’t notice it. I can’t speak to experience to whether you would need an air hole in the “U” — I just wouldn’t use it at all.

      • Not_Bob

        I think I’m with you and would not use the inverted U; however, I still can’t see it working with the sump end submerged, too. Thanks for getting back to me.

        By the way, I hope to try a Herbie overflow in a couple of weeks. I’m looking forward to it.

  • http://leapfrogthis.blogspot.com Shane Hopkins

    I assume this system would make the BeanAnimal Overflow System Obsolete due to the fact that this system is MUCH less complex. Anyone have experience with both or know of any features in the BA system that the Herbie does not cover? The Bean Animal Silent Overflow can be seen at Reefcentral dot com in the DIY forums. Thank you GMAC for posting this simple system with thorough explanation. I will be incorporating it into my current reef build. Cheers!

    • http://gmacreef.com gmacreef

      I am not sure that the Beananimal system would be made obsolete, as it does have the advantage in that it deliberately prevents a siphon, meaning that it can go into full operation in seconds while the Herbie takes longer (usually under a minute) for air to be purged from the system and go back to silent operation. I have seen a few demonstrations on YouTube of the Beananimal, but nothing to convince me that it’s vastly superior. The main advantage I see with the Herbie is that it uses only commonly available parts, way less fittings and is just plain simple. Most people don’t want to spend hours rounding up parts, researching, and then assembling an overflow. Although there is a decent writeup of the system basics on the beananimal website, people who have questions have to go to the massively bloated Reefcentral thread to get their questions answered. I also think personally that the idea behind using the beananimal awards a lot of supposed benefits to using a long Calfo-style overflow which is in many cases overkill.
      Here is a link to the guide.
      Bean Animal Overflow System

  • Azeem Khan

    Is an internal overflow box absolutely necessary?

    • gmacreef

      Well that depends. The siphon and the emergency line will operate the same whether or not they are contained in an overflow box. Overflow boxes provide a few benefits: they allow you to keep the water in the tank at a set level, hide ugly PVC pipes, and provide more protection against debris for the main siphon drain (which should have a strainer on it).
      If you are not running an overflow box at all then there will be a large volume of water that will fluctuate between the tank and sump during the stop/start of the Herbie operation that you probably don’t want. The best looking way to do it in my opinion is to run an overflow box that is mounted to the back of the tank for your standpipes, with a channel for your overflow cut through the glass. See the pic in the post.

    • gmacreef

      Well that depends… The siphon and the emergency line will operate the same whether or not they are contained in an overflow box. Overflow boxes provide a few benefits: they allow you to keep the water in the tank at a set level, hide ugly PVC pipes, and provide more protection against debris for the main siphon drain (which should have a strainer on it).

      If you are not running an overflow box at all then there will be a large volume of water that will fluctuate between the tank and sump during the stop/start of the Herbie operation that you probably don’t want. The best looking way to do it in my opinion is to run an overflow box that is mounted to the back of the tank for your standpipes, with a channel for your overflow cut through the glass. See the pic in the post.

  • Kevin M

    My herbie overflow has to be “restarted” every time the return pump is turned off. The last pipe from in intake goes fully into the water in my sump and if i turn it off and back on again, I have to take the last pipe off and let it drain for a while before I put the pipe back on or else it will just go through the emergency drain and not use the actual drain pipe.

    • http://gmacreef.com/ gmacreef

      If your main drain siphon is not restarting on it’s own in under a minute it then it could be a couple things. This can usually be corrected by shortening the standpipe height in relation to the emergency drain. There has to be a sufficient amount of water to create enough pressure in the main drain to purge the air inside and restart the siphon. This can also be helped by making sure the drain line exits into the water level in the sump by only a few inches so the air in the line can escape easier.

  • George Ziras

    I want to thank you for your very informative article about Herbie overflow.

    Recently I design my own in a 75g tank. I have the e-shopps nano overflow and the eheim 1000 pump as return.

    I’m facing the following issue with my herbie. When I’m closing the ball valve to reach the point where my emergency hole is, automatically the water level in my display is rising as the water in the overflow box behind my tank rises. This is normal? Also it seems that I can’t adjust the water level in my display tank by lowering the overflow box, maybe there is a relationship with the return and siphon?

    Best Regards

    Ziras George – Greece, Athens

    • http://gmacreef.com/ gmacreef

      Thanks for your comment, but I really can’t give you any advice on this, as I have no experience with any type of hang on overflow box. The design of them is just too flawed IMO, and to be honest I am not sure how anyone can trust that these devices will restart a siphon before the tank overflows. To be blunt – I think that they are garbage… yet also unfortunately too commonly seen in this hobby. Drilling the tank is the only way to go and much easier to do than one might think.

  • Brian Fischer

    What is the advantage of placing the valve near the overflow rather than at the sump? Wouldn’t the pipe fill faster with the valve installed near the sump?

    • http://gmacreef.com/ gmacreef

      I don’t think the exact position of where the valve is installed on the siphon line makes any discernible difference at all as far as the mechanics of the siphon are concerned. It is more a matter of convenience and having easy access to reach the valve with your hand to make those fine adjustments. The advantage to mounting it high in my case is it’s a lot easier to dial in the flow when you have your hand on the valve and a sight-line of the water level in the overflow. If the valve is mounted under the cabinet, then that makes it a bit harder because you’ll have to go back and forth. On my tank I opted to install it under the overflow so I could reach it while standing next to the tank.

  • Boyu Chen

    Hi!

    Great website, much better illustrated and explain! Better than BA website….BA website got just too much redundant words too little important details…..

    But i got a real worrying question regarding Herbies, you said, You should be aware that: It is not completely a “set-it-and-forget-it” method… It needs to be regularly inspected and properly maintained.

    What should i inspect and maintain? I am not following on that!

    One more to go… On the BA web he said his is absolutely “set and forget” type….. But i don’t understand the very basic of his system about two hose face down, that makes me worried when pump tuen off, and the drain wont start….. Do you know how BA start it self?

    • http://gmacreef.com/ gmacreef

      The statement “It is not completely a ‘set-it-and-forget-it’ method… It needs to be regularly inspected and properly maintained” is just me beating the drum that you should use a strainer on the main siphon drain, and it is something you need to be keeping your eye on. Depending on what type you use, it will eventually become dirty. Cleaning isn’t normally necessary too often, but is critical for problem-free operation. The use of a strainer is really the only way to claim that the method is completely safe in my opinion. Doing this will ensure that the Main siphon drain is protected — as a clog is most likely to first occur at the narrow choke-point of the valve. I added a link to the strainer section at that part of the guide to clarify.

      The topic of choosing a Herbie design vs. Beananimal design is really a subjective matter of personal taste and what level of extra safety/redundancy you desire on your own tank versus how much time and effort you want to spend researching and building an overflow.

      I’d rather not discuss specific questions about the bean design here as it is out of the scope of this post, but may cover the method in another post in the future. Thanks for commenting.

      • Boyu Chen

        Thank you for replying, I rather say the Heribie is easier to understand, the strainer, ball valve, they are easy to understand why there are there, to my knowledge, understanding your design, is it actually the way I would do if I have not yet seeing yours.

        I know the difference between bean and heribie, the bean is just one pipe more. I am not going too anal with the topic, it is not the next UFC fight, the main question here is, how well the silence and “set i and forget it” the herbie will go? I know you said watch out for clog on the pipe, i think people with a tank will always go tinkle with them….so no problem there, I am all freshwater, no marine water, no sea monster thanks… so if the pipe is check every day, (i mean we all go watch our tank daily right? haha that is the reason for it…) Can I say the herbie is “set it and forget it” design? I really really want it to be said from your mouth…!!! because I don’t want to waste money and make something not gonna work well, but again, I never build a overflow before, this is my first round, so I would very love to see a knock out!!!!! can you please let me know it is “set it and forget it” like I assume it to be?

        Last question, what fitting would you use on the drill bottom tank?

        So many questions, sorry about that, I really love your simple design, and it will be my way to do it too.

        BTW, my tank size is 100cm L x 50cm D x 50cm H about 240L.

        Best regards

  • glen segarra

    Thanks for taking the time to put all this up in a way that is easy to understand. You’ve saved me hours!!!

    Is there any reason not to make the emergency overflow a slightly larger diameter than the main drain?

    • http://gmacreef.com/ gmacreef

      Glad it helped you!

      You can make the emergency drain larger in diameter, but it’s not an option for everyone who is just retrofitting an existing tank with the method. If you have 2 pre-drilled holes, then yes — the larger one should be run as the E-drain to get max capacity out of it.

  • JaCoBz2007

    Hi, where can I purchase these strainers or is there another word for them as I can’t find them anywhere.

    • http://gmacreef.com/ gmacreef

      They are called Bulkhead Overflow Strainers and you can get them from Bulkreefsupply. Some people also create them DIY with a tube made out of plastic mesh.

  • Chris Swanson

    You rock! I started with a durso drain and the bubble draw was not acceptable. I had already drilled the tank and only read most of this article when I thought: a tee! Then I saw Boromir. I laughed with that all day. I drilled a third hole in my living room and now have a Herbie and no bubbles. Thanks!

  • mick

    Does anybody know of anywhere in the UK that you can buy these strainers from because I can’t seem to find them anywhere?