An overflow box is used to drain water from your display aquarium down into your sump or filtration system.
The overflow box itself consists of a weir along with drain pipes and other plumbing in order to get water out of your tank and down into your sump. Various types of overflow boxes and plumbing methods are employed to accomplish this task of draining your aquarium. No matter which option you choose, all of them accomplish the same thing.
We cover the three most popular methods used to create an overflow system: Durso, Herbie and Bean Animal.
Noisy drains can be problematic when it comes to transitioning the water from your main tank display to your sump system because of the noise water creates when traveling through the pipes and then splashing down into your sump. The Durso drain is a trendy way to plumb your overflow that helps with noise reduction.
The Durso is easy to install and does not take up much space making it popular for smaller aquariums with sump systems. Instead of having the water crash down into the bottom of the overflow box, the Durso allows for the water to rise and enter the drain through an attached elbow as demonstrated in the diagram. The Durso standpipe has a small vent hole on the top elbow that prevents a siphon from forming in the drain pipe.
A single vented standpipe such as the Durso drain does not handle high flow rates very well. Gurgling becomes louder as the pipe fills with more water and therefore larger pipe diameters (1.25″ +) are used to help the drain handle higher flow rates and stay quiet. The single drain pipe is then reduced in diameter before going through the bulkhead and entering the sump. The end of the drain is typically submersed below the water level in your sump to help avoid splashing noise and reduce salt spray.
Something to keep in mind when considering a Durso standpipe is that although they take up very minimal space and only require a single hole in your tank, you do not have a fail-safe or back-up drain. While it is rare, in the event this single standpipe gets clogged, your display tank will overflow.
When there is more at stake than just noise there are overflow options that also provide peace of mind. The Herbie Drain is an effective way to keep noise to a minimum while helping prevent a drain disaster.
The Herbie Drain is composed of two standpipes. One acts as the main drain pipe and creates a full siphon when pulling water from your tank. The other is used as an emergency drain should the main drain become clogged and sits a bit higher than the main siphon pipe.
This drain style is ideal for larger aquariums because you can move higher flow rates compared to a Durso drain. The main drain will have a strainer keeping aquarium inhabitants like snails from getting clogged in the drain line. The strainer should be cleaned frequently to prevent a blockage, the emergency drain is ready should this happen.
The main drain has an adjustable valve allow for fine tuning of the drain siphon speed resulting in quieter operation and optimal flow through your aquarium. Both the main siphon drain pipe and the emergency pipe are submersed underwater in your sump to help reduce noise from splashing and salt spray on the surrounding areas.
The Herbie is a great system for a variety of tank sizes because it can handle higher flow rates without a drastic increase in noise. They will require two holes in your aquarium which means a Herbie drain takes up more real estate inside your tank. The ability to control the drain rate and the peace of mind you get with the emergency stand pipe makes this a very popular option.
Bean Animal Overflow
The Bean Animal drain is a hybrid version of the Durso and the Herbie drain and literately employs both drain styles to accomplish high flow rates while operating near silent.
In the diagram above you will notice the Bean Animal Drain uses three drain lines which means you need three holes in your tank or overflow box. The main siphon drain is a Herbie style pipe, the secondary vented standpipe is a Durso drain and the third is the emergency back-up drain.
The reason this drain operates quietly, even with high flow rates, is because you can reduce the rate of flow using the valve on the main siphon drain to the point it operates silently. The Durso pipe then drains the additional water required to accommodate your desired rate of flow through the aquarium. With the Bean Animal, the two drains would be submersed below the sump water line for effective, clean, and silent operation.
The end of the emergency drain can be cut above the sump water level. Should it ever be in operation, the splashing into the sump will act as an alarm, alerting a hobbyist that something is wrong with the drain.
The Bean Animal is one of the best ways to move water out of your aquarium and into your sump. It is quiet, handles high flow rates, and includes an emergency back up drain. The downside is the amount of space required to get all three drains installed onto your tank.