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:
- Run a completely silent drain from the overflow to the sump below
- Have it be completely fail-safe from possible flooding with proper design and maintenance.
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
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.
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
Due to the need for fine levels of adjustment, installing a quality valve is suggested.
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.
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.
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).
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
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.
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.
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.
Best Practices for a Problem-Free Overflow Box
Doing these things will make the main siphon less likely to clog.
Use a Strainer
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!
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:
- Is the water level where it should be?
- What is the condition of the strainer? Does it need cleaned?
- 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.