We would ned much more information to answer starting with where you live. Also tell us all about the struture, is it a home or what. Is this in a basement or where?

Sorry it's an upstairs bathroom at home, it has standard floorboards and I just want to make sure I have the right depth for the pipe! I've heard horror stories of screws going into pipework and I just want to make sure I'm covered in case of said horror stories in the future! Thanks

Oh and I live in the UK if that makes a difference? Thanks

To be on the safe side, I would just put them in the middle of floor joist. This way you are covered top and bottom.

If there are any limitations as to how deep you can install the pipes then anywhere the pipes pass through wood, that could take a screw or nail, be sure to use a steel nail plate/guard. I'm sure there are a number of pipe protection devices available at plumbing supply stores in your area. Ask what they stock if you have no choice but to put a pipe in a potentially hazardous place.

Well, typically, carpenters use 8D or 10D ring-shank nails to install ply over joists. If screws are used than they usually shorter than nails. So install your pipes bellow the reach of 10D nail and you should be fine. Hope that helps... Milo