A/C Flush

[BobFino]

I have flushed my lines out with fresh water but I would like to do a closed loop with some descaler like Barnacle Buster. The supply line from the sea strainer is easy. However, I cannot find where the return line is feeding the outlet tubes. Since it drains from both sides there must be a Y somewhere in the line to connect to and flush the system. I see nothing of the sort in the engine room. Any help is always appreciated.