Whether you’re designing a new ballast system, or trying to upgrade your existing system to fill and drain faster, one common question is how best to design the system so it is as uncomplicated (and also inexpensive) as possible. One of the tools that we use when helping people design a custom ballast system is a product called a vented loop.
As shown above, a vented loop is a “U” shaped plastic fitting that is installed in series with the fill pump when using aerator pumps. During filling, the vented loop is invisible, functioning as a section of hose without any limitations. The beauty of the vented loop only comes into play when the the fill pump is turned off, which means there are no drawbacks to implementing its use. When water is not being forced through the fill hose, air (but not water) is allowed to pass through a vent at the top of the loop, which allows the column of water from the vented loop to the fill pump to drain down to the level of the pump.
It is this column of air (typically at least two feet long) that prevents water from siphoning into, or out of the ballast bag when the pump is not running. Many people are under the impression that water is forced past the fill pump due to the boat running at speed, but it’s not possible to develop that much pressure, and it actually just the siphoning process that allows the bag to fill or drain. The vented loop solves that problem by creating a break in the column of water running from the pump to the bag, so siphoning is not possible.
To function correctly, the vented loop needs to be installed close to the ballast bag in question, and as high above the water line as possible. For forward ballast bags, the typical installation location is under the driver’s dash up near the windshield. In the back of the boat, up under the gunnel, whether in direct drive or v-drive boats, is typically the best location.
If you have any other questions about the vented loop in particular, or ballast systems in general, please feel free to contact us.