Down the Drain is an earthy track composed of 4 pipes connected to a pool of oily water. These pipes are the bloons' paths. This can be a very hard track since it is composed of 4 paths (entrances and exits). At first, bloons inside the well went out of it, merging into 4 paths, then turn around the pipes and exit them. Buccaneers, Submarines and Turtles can be built into the pool of water. This track is arguably the hardest track in the game, possibly even harder than Bloontonium Lab as the track has 4 short paths and the only intersection is at the entrance.
- Main article: Down The Drain/Strategies
|Down The Drain Bronze||10|
|Down The Drain Silver||25|
|Down The Drain Gold||50|
- This is the only track in Bloons TD 5 to have 4 paths that bloons appear together, with 4 entrances and exits. Others being Country Road and The Eye, but one-by-one path appearance of bloons.
- This is arguably the hardest track in Expert Difficulty, possibly even the hardest track in the whole BTD series. Other candidates would be Monkeys vs Bloons, Triangle of Insanity, Bloontonium Lab, Crypt Keeper (With Reverse Mode turned off), Tar Pits and BTD6's Workshop.
- This is the third Expert track to contain water for water towers, with the first one being Castle and the second one being Double Double Cross.
- Despite the fact that it has 4 very short paths, it is rated expert and not extreme due to the fact the track isn't short enough to be Extreme.
- This is may also be due to the difficulty of the track, and Ninja Kiwi wants to give chances to the players, so they don't have to waste Monkey Money trying, they can save, and they can test out strategies in Sandbox Mode.
- However, due to the differing costs in Monkey Money to play Main Street and Bloontonium Lab or Tar Pits, it would be possible to rate it extreme and make it cost nothing or anything lower than 25 to be merciful to a player.
- Like Mount Magma, Bloons appear in the middle of the track.