by jedums »
Sat Feb 16, 2008 11:36 pm
I can give the only two answers.
1 you mentioned that the pipes are new, so I think the 'run' is too steep. roughly for every 4feet the pipe drops no more than an inch, any more and it 'draws' the seal on the sink trap which is like someone gasping for air.
2 You have a blocked drain outside. More likely!!.