The threaded, in-line Venturi valve is situated after the output from the pump and prior to the intake on the skimmer.
Different models incorporate this in differing manners, but this is a classic installation method. An airline may be placed over the Venturi's nipple to quiet the noise created by the air siphon.
A hard-plumbed, dedicated water pump provides the velocity necessary to make these style models work efficiently.
Here, I show two ball valves installed between the sump bulkhead and the pump's intake, also at the output nozzle. This allows the pump to be removed from the system without further disassembly.
Not shown would be a third, optional ball valve installed at the skimmer's output tube, below the water line. On some models, this third valve is required to create back-pressure in order to maintain water-foam levels inside the reaction cylinder. The box that this example is shown in, is a typical sump.
I have left out the water return pump, bio-tower (if equipped), and other sump accessories that you may use.
Collecting The Gunk
The skimmate can be directed into a larger container WITHIN the sump to eliminate overflows, and for drained aquariums there is no other option for this point!
For more do-it-yourself sump and overflow box projects, go to our DIY Corner Resources.
In Part 5 I cover soft and hard-plumbing installations, using valves and their various uses when installing skimmers, and the pro's and con's of 24/7 skimming within a closed system.