I am converting a detached garage into an apt. What would you recommend for underground supply pipe from house with the following conditions: municipal water water supply, aggressively treated with chlorine- ammonia mix, has been cited as cause of leaks in older copper installations, 3/4" hard copper at rear of house with 1/2" ball valve reduced on it, 80' trench run in sandy soil,( no rocks, there is possibility of tree roots causing some lateral movement, pipe will have some turns),apt. fixtures will be: 1 bath lav. 1 w.c. 1 shower, 1 kitchen sink, tankless water heater Leaning towards using sweated, hard copper in apt. I am concerned about the following: durability, low danger from pipe leeching, pipe i.d. for adequate pressure and flow, cost. I am a former general contractor on fixed income and know my way around a shovel so I will be doing work myself and I want it to meet or exceed codes. Project in w.p.b. fl.

Greetings from Sarasota,
I would install 3/4" schedule#40 PVC for your water service. Replace that old 1/2" valve with a 3/3" one.
If you're concerned about pin hole leaks in the inside copper consider piping with PVC and CPVC. Good luck, Tom

You will find different opinions on the subject in this forum. Tom lobbies for PVC, I lobby for copper. In my area, PVC would not be allowed for your application.

As far as size goes: With developed length of 80' I would go with 3/4" pipe. You are not giving us pressure in that run , but : If you have low pressure, go with 1". For us, copper works fine. If you worry about exposure of copper to the soil than sleeve it.