robgraham wrote:
The garage is having a makeover, including getting guttering. What
pipe do I use for the underground run to the outlet for the septic tank
?

Thanks

Rob

You don't run rain water to a septic tank. I hope you meant that you are
running the pipe to where the outlet of the tank itself goes..


It should go to a soakaway..or of you are really lucky and the health
and safety lot haven't seen it, into a ditch.

4" standard pipe is adequate.