Z-Flex Z-Vent 3 inch Condensate Drain Kit 24 inch (2SVEDTK24) for tankless water heaters. This kit is to be used for all vertical installations and horizontal installations that are greater than 5 feet in total length in any direction. The 24 inch condensate tube is made of 3/8 inch (I.D.) high temperature silicon to prevent corrosion and should be filled with water to prevent gases from coming out of the tubing. The tubing should be fed into either a drain or a collection bucket through some form of piping or tubing although the amount of water that will come through the condensate drain is limited.