No one here installs 5", I couldn't even tell you. 4" pipe is < 30 cents/ft. 6" around 70 cents/ft. If ever there was a year to convince a guy that tile on closer-than-recommended-spacing was beneficial, this has to be it. Soil type, spacing, and depth very important to determine drainage coefficient. Just as an example, recent numbers I ran on drainage coefficients: Good black land (Drummer), installed 3' deep. 100' spacing 0.168" DC 80' 0.259" DC 60' 0.449 50', 0.634 40' 0.963 Using this pattern (halving the spacing gets you 4x the drainage coefficient) and taking some liberties with your example: If 5" on 50's would happen to get you a DC of 0.25" 4" on 40's gets you a DC of 0.39" (1.56 times the drainage coefficient of the 5" on 50's - which is a YUUUUGE difference in how fast your soils could drain, if everything else is sized correctly). So ... if your 4" had adequate capacity towards the bottom of your tile run (enough slope) you might be ahead to squeeze them together, dig a few extra connections, and just run 4". It's site specific and you'll have to figure your own breakevens, etc. We have some good black land tiled on 50's instead of the more common 80's. Our DC is approaching 0.67". Those crops look fantastic this year! But, they also have high water-holding capacity so they aren't over-drained. |