Jacob’s Blog

Recapping…

This is more of an afterthought to my Herbie Overflow post than anything else. I’d like to recap a couple of points…

• Murphy’s law is always working against you. Eventually a snail, fish, or some algae is going to restrict or completely block your overflow standpipe.
• Having multiple standpipes reduces the chance of flooding due to a blocked pipe.

Use of standpipes is popular because they raise the water level in the overflow box and quiet down the waterfall effect. The higher the pipe the less waterfall. For many of us, myself included, this means that the air inlet on your standpipe (most designs utilize an air inlet) is above the rim of the aquarium. This is fine, however it eliminates an intrinsic safety mechanism of the standpipe.

Intrinsic Safety Mechanism?!?

By its design any standpipe with an air inlet runs at partial siphon, or zero siphon. If the air inlet becomes blocked a siphon will form. When a siphon is present the water handling capacity of the pipe will increase until the siphon is broken. Whether or not we realize it this is also a built in safety mechanism. In a situation where the air inlet is below the rim of the aquarium, any problem leading to an increased water level in the overflow box and/or aquarium will eventually submerge the air inlet of the standpipe. This will result in a siphon being created in the standpipe and thus the pipe will instantaneously increase in water handling capacity; in many cases preventing a flood from occurring. Of course if a blocked standpipe is the culprit causing the high water level to begin with there is no guarantee that a flood will be prevented; it depends on the severity of the blockage.

Getting back to the scenario that may be common for many of us, if your standpipe is above the rim of the tank it’s clearly never going to become submerged as result of increasing water level. Instead a flood will occur.

Don’t Defeat the Safety

One way to keep this intrinsic safety functional with the air inlet above the tank rim is to use a reducing bushing at the top of your standpipe and fit it with a pipe-to-tube adapter then run a short length of tube down into the overflow chamber making sure it is below the rim of the tank (but not normally under the water level). If the water level ever rises to the tube the air supply to the standpipe will be cut off and a siphon will form. This is how my Durso pipe is set up. I also keep a valve on the air tube to fine tune the air supply to the standpipe (this is much more convenient than trying to drill the right size hole for an air inlet). In the picture below you can see the Durso on the left with the tubing coming out the top. In this case I had the tube pulled to the side but usually it’s looped down into the overflow box.

That’s all there is to it. While this isn’t a foolproof way to avoid a flood it does provide one more line of defense - and sometimes that’s all it takes until we can get home from the office to discover and fix the problem. Good luck, and stay dry!