The ABS 1.5" Double Ell Tapped is used to divide the flow of greywater into two equal sections in a branched drain system. The double ell should be placed on a brick or stone and leveled so its perfectly flat. To get an equal split, you need a straight run of at least 2 feet entering the fitting, if you don't have this distance the water may not be equally divided. The cap can be removed for cleaning out the system in case of clogging. This fitting should be located in an accessible spot, like inside of a valve box. Typically 1.5" double ells are used in the entire branched drain system, or in all splits after the first in a system that used 2" pipe.