A bottom drain system functions to remove the waste out of the pond and ensures a well-circulated water flow. Without it, stale and aged water will not be easily drawn out especially if there’s a “dead spot” due to your pond design preventing fresh water from going in to replace the ones taken out. The bottom drain and the vortex chamber filter actually work hand-in-hand supporting each other to ensure that in the end as much as possible water is taken out from the system and then treated by the external filter before it is returned back to the pond.
Usually old technology of a bottom drain device comes with just the top piece cover dome but recently most of the new units sold in the market are the one called the aerated type which basically has an inlet tube for air supply to go in and aerate the pond at the same time. For better understanding on it works and to help you visualize what is being described here, just refer to the diagram shown above so that it will serve as a guide to make your installation process becomes easier.
As you can see from the details, there are actually two major advantages using the aerated bottom drain system. First, the unit designed with the extra air bubbling feature actually allows more water to be drawn out easily sucking out dirt and fish waste which would otherwise remain stagnant collected at the bottom of the pond base. As the air moves in the opposite direction floating to the top, the counter flow movement actually creates a suction force that draws water easily from its surrounding area going to the drain pipe and then leading to the pond filtration system. Conventional bottom drain device although plays the same function as the old technology but however, in terms of efficiency, the performance and desired result wasn’t similar to the aerated type. Thus, most koi hobbyist will tell you to switch to the new system as it will offer more benefits and flexibility.
Another reason why most people would recommend using the aerated bottom drain system is because since it has an air tube inlet going in; this offers extra aeration capacity going to the pond system. Air bubbles that rise to the surface will create and allow more gas and water exchange surfaces and apart from that, naturally it also makes your koi pond look much nicer and presentable.