Herbie Style Overflow Guide (Here Is How It Works)

This is a complete guide to setting up and using the Herbie style overflow on your saltwater tank. Contrary to what you might hear from others who use this method, the Herbie overflow when set up correctly is completely silent. No noise is one of the huge benefits of this method. There are other benefits as well which we will get into. 

The term “Herbie” became popular after a forum member named Herbie posted this method of overflow, and it started to get a ton of attention. It quickly became a commonly used overflow method used by many, and it’s my preferred method of draining water from the display tank to the sump. It is easy to set up and works very well.

Herbie style overflow – overview

The Herbie style drain requires 2 standpipes. One of the standpipes is the primary and creates a full siphon. The other drain is used as a backup in case the main drain gets clogged.

 The Herbie style overflow is great for larger tanks which require a high flow rate. The primary drain should have a strainer on top to prevent debris and anything else getting inside causing a blockage. The great thing about this system is if a blockage were to happen, you have an emergency backup drain to save the day.

The primary drain will also have a ball valve or gate valve to control the rate of water flow precisely. Being able to fine-tune the water flow will allow for quiet operation and proper flow through the whole system. Both of these standpipes will be submerged underwater.

The annoying gurgling and sucking water sound will not exist once the Herbie overflow is set up and running properly. 

Pros of the Herbie overflow:

  • Quiet operation
  • More water flow
  • Emergency backup drain 
  • Fail-proof when set up properly
  • Easy to set up and operate

Cons of the Herbie overflow:

  • Takes up extra space in your tank – requires 2 holes

How to set up the Herbie overflow

Items you will need: 

Keep in mind the amount and sizes of these items will vary depending on your tank size and setup. 

  • Overflow box with 2 drains (either in the tank or hang on)
  • Plumbing (PVC or tubing)
  • 1 strainer
  • 1 ball valve or gate valve (use the union valves if possible)
  • 1 Union if not already included on the ball valve

Other plumbing parts like elbows, reducers, PVC glue, will be necessary and need to be planned out ahead of time before setting up the overflow. For the purpose of this article, I will just stick to the actual set up of the Herbie overflow itself.

Overflow box showing Herbie style overflow
                        Overflow box showing Herbie style overflow

#1. Strainer on main standpipe drain

Strainer on main standpipe drain

The strainer will prevent any debris, fish, or snails from entering the standpipe and clogging it.

What height should you place the main drain standpipe?

This should be placed 6″ below the height of the secondary standpipe. The reason the pipe is placed approx 6″ below the emergency drain, is to allow room for water fluctuations as you fine-tune the water flow with the valve. This will eliminate any noise or water gurgling as it drains to the sump.

#2. Valve – either a ball valve or gate valve is preferred

ball valve
gate valve

The valve’s purpose is to allow you to control and fine-tune the flow rate of water draining to the sump. You will need to match the flow rate of the return pump which returns the water from the sump back into the display tank. This can take some time to achieve and you may need to make very slight adjustments to get it just right.

A gate valve will be more precise versus a ball valve. I have used both without issues. It is also easier to fine-tune this water flow if you are using a controllable return pump. If you can adjust the flow rate of the return and match it with the drain from the overflow, you are all set. I also recommend that you use a union for your plumbing.

Either a spears gate valve or a true union ball valve.  They are a smart addition as it will allow you to remove the plumbing without taking the whole set up apart. If you don’t have the option of using a union valve, you can add a single union separately between the valve and the bulkhead.

#3. Secondary drain standpipe (emergency drain)

The secondary drain is what gives you peace of mind with the Herbie style overflow. In the event the main drain was to become clogged, the emergency drain will take over, and the system will continue to run. This pipe is connected directly to your sump with no strainers or valves. You want to allow the water to flow unrestricted to the sump.

What height should you place the emergency drain standpipe?

The height of this standpipe should be just below the level of the water line in the overflow box, so a trickle of water is allowed to enter. Water should not drain through it when the main drain is operating normally. Only a trickle of water should be allowed to enter. The height will also be about 1/2″ below the weir of the overflow box.

How to set up the Herbie style overflow

Herbie style overflow

The great thing about a siphon drain is that you can have a full siphon without air entering the system. It’s pretty much silent. The key to having an overflow system work properly is you need to match the water flow rate of the return. This is where the ball valve or gate valve comes in.

Once the overflow rate and return rates are matched, it will stay running like this consistently until it is interrupted.

To start the system, open the valve to the fully open position and slowly begin to close it as the siphon starts. As the overflow fills up, make these fine adjustments of the water flow using the valve to match the return.

You are looking to have the water level in the overflow so that it is right at the height of the emergency drain. Just enough to let a small trickle of water flow through it.

In order for this to work, once the water is flowing at the same rate as the return, start to slowly close the valve until the water reaches the height of the emergency standpipe.

Allowing this small trickle of water through the pipe will prevent you from constant adjustments that are so small it would be difficult to do.

Plus it keeps the emergency drain open in case it is needed. At this point, the water will stabilize and flow consistently and silently. You won’t even know it’s running.

Herbie overflow standpipe heights in the sump

standpipe heights in sump

Both the main drain and the emergency drain will enter into the sump. It’s important to have these drain outlets positioned about 1″ below the water surface in the sump.

You don’t want to position them any deeper than 1″ as they will have a difficult time purging air anytime the system starts up.

Herbie style overflow considerations

There are 2 main areas of concern with the Herbie overflow. Actually any type of overflow is affected by these issues.

  • Power outage
  •  Clogged overflow

What happens when there is a power outage?

If there is a power outage, the return pump will stop operating unless you have it set up with an emergency backup power source. The siphon on the overflow will continue to drain water into the sump that will not be returned, and your sump will continue to fill.

When setting up your sump system, this is one of the biggest factors to consider.

You need to allow for enough space in your sump to hold the amount of water that drains from your display in the event of a power outage. The siphon will continue until there is a siphon break caused by the overflow weir and the strainer on the main drain.

Once the water level gets below that, the water will stop flowing.

Once the power starts back up, the return pump will push the water back into the display. Once it is high enough to overflow, the siphon will restart automatically.

Once I am finished setting up my Herbie overflow, I will simulate several power outages to make sure the system will run properly.

I have never had a problem.

What happens when there is a clogged overflow?

As mentioned, if your main drain were to become clogged, the emergency drain will take over and water will continue to flow. This is a huge benefit of the Herbie style overflow. Once you unclog the standpipe, it will run as normal again.

To avoid a clogged standpipe, you should use a cover on your overflow to prevent critters or debris from entering.


In my opinion, the Herbie style overflow is the best way to go. Not only is it completely silent, but it offers a fail-safe with the emergency drain. It is easy to set up and once you get used to it and have the flow rate set just right, it works flawlessly. Make sure you plan ahead of time to set up the equipment you need. The Herbie overflow will work on any sized tank, so if you’re setting up a new sump system or a completely new tank, try the Herbie overflow. You will love it.