What is the best way to connect 3 separate backwashing systems to a single 1/2" drain line?

[Hyrepower]

I have a Carbon/KDF filter tank, Fluoride Tank, and Softener that all require backwashing. I can not find any 3 into 1 fittings to connect to the 1/2" drain line. I wanted to use 1/2" stainless steel compression lines and connect them to a brass W (That I can not find). I was going to install a 1/2" compression fitting to the PEX drain line so I could thread the W adaptor into it, then connect each 1/2" from the 3 water systems to the W.

I can not find the parts however. Does anyone know where I can find the parts, or know a clean easy way to do this?