I need to connect a tee to a pipe buried 21" down, well above the frost line. This pipe carries water collected from the hill behind my house to just above a storm drain in the street in front of my house - it doesn't have anything to do with my house plumbing or anything else, just delivers the water collected by a buried perforated pipe. The hill is so water-laden that new trouble areas keep emerging s0 I dug a trench system that is working very well but I need to connect it to the pipe going to the storm drain. I would like to use a saddle tee with flexible fittings but can only find ones that are designed to connect to schedule 40 pipe. I've read about workarounds like using a gasket to get the tee to fit my pipe but they are not specific enough for me to feel confident about doing it. I really want to avoid cutting the pipe and using a standard tee if I can. Any thoughts or specific guidance would be much appreciated.