while perusing the internet i find this
http://www.wetwebmedia.com/SystemPIX...Oneinchart.htm
basically stating a 1 inch drain line will be noisy because it cannot effectively handle more than 300 gph without going full siphon
this explains why my 75 gallon is noisy and my 29 isn't.. both have 1 inch drain lines, just different bulkhead sizes
im wondering if a CS90 overflow box will support a 1.5 inch bulkhead or if i just need to buy the cs150?