2) All CYL850T and CYL851 valve have O ring tails one end and 15mm tube to compression fitting into the valve... some of the compression nuts on the valve has enough (about 2 turns) turn to have a water tight compression grip on the tail .. most of them have about 20% + turn on the thread left to make it a watertight compression.. we haven't tested for water tightness however it is a concern.. there must be enough turn left on the thread to tighten the nut on the valve body so that it can be a watertight compression fitting on the tail pipe