How do you figure the size of pipe needed to drain certain square footage of roof? Neighbor has ~120x70 indoor riding arena and wants to rout the downspouts into pipe and daylight it on the other side of the fence. I'm guessing i take some rainfall rate and the square footage of the building and get the flow per hour and size accordingly, but i don't have any specifics.
I would search rainfall runoff calculator on google, there's lots written, on the subject, had classes in college...:my2c:my2c Here's one: http://www.calctool.org/CALC/other/default/rainfall You then need to plug in your GPM figure, from above, to a pipe size calculator, similarly... Here's one: http://www.1728.org/flowrate.htm Always a good practice to plan for the rainfall amount of a 100 year storm, in your area, that way you're dead, or retired before a bigger storm comes to wreck your work... :drinkup:drinkup
What size downspouts did the gutter company put in it? The minimum size pipe we put in the ground for down spouts is 4" SDR 35 plastic pipe, depending on the length and number of gutters I'll tying in I'll bump it up to 6" SDR 35. FYI, 4" SDR 35 will handle the same amount of water as 6" corrugated pipe, not to mention the water isn't sitting in it when it freezes and it is much heavier duty. How many downspouts on each side of the building?
You want to design it so that the rain has somewhere else to go if the pipe clogs up or is overwhelmed by an occasional worm drowner. If some rain falls off the roof during this type of event it is unlikely anyone will notice anyway
So, i got a little lost in trying to calculate the water velocity. I know there is away to calculate water velocity based on slope and coefficient of friction, but all I find is Manning's Formula, which requires a pipe size to find hydraulic radius. This one of the many things i know just enough about to be dangerous. Edit: Just found some pretty pictures on ADS's site that graphs flow, slope, and pipe size. Can't say i'm disappointed somebody did the math for me.
Actually you hire a licensed plumbing contractor who is trained to calculate this. When you do it and it fails and causes roof damage or failure, then you will either be out of business or on the hook for the building.
Always a good practice to plan for the rainfall amount of a 100 year storm, in your area, that way you're dead, or retired before a bigger storm comes to wreck your work... :drinkup:drinkup[/QUOTE] BaHaHA we had five 100 yr rains this year...