Gutter Sizing Calculator

Does anyone know of a good online calculator for determining the correct size of gutters and downspouts? I was looking at the tables in my sheet metal books and thinking how much easier it would be to enter the variables on my computer and get the answer...yes the lazy days of summer are here B)>>>

Thanks everyone, Ed that is the same info I use for calculations- I was just wondering if anyone had simplified it to the point of entering roof area and rainfall intensity etc. and getting an automatic calculation. >>>

When I was serving as a draftsman for a local A/E. our engineers were doing developmental work in concert w/ the Josam Company, on RWC s for dead level or flat roofs. As I recall, physical location, rain intensity, etc. were among the variables considered. It was interesting work, that saved the building owners lots of money, for the reduced flow velocity enabled smaller and fewer outlets. On the rain sewer alone the standard pipe size according to existing codes was 60", howeever. w/ the new design a 48" pipe was used. (The pipe length was about 600 ft.)>>>

A lot depends on the type of rain storm you are talking about. On a really severe rainstorm, most gutters will overflow for a bit anyway. The biggest thing is to keep the gutters and downspouts you have clear so the water can flow freely.>>>

Try this site for sizing and calculations.

http://www.egutter.com/s.nl/sc.2/category.2092/.f

http://www.egutter.com/s.nl/sc.2/category.2092/.f

Also, they have the water table information in the SMACNA Manual.

Ed>>>

On a related subject - the sizing of downspouts. The only info I can recall on the subject was published in a Barrett Spec book - and as I remember, it was 150 sq.ft. of area for 1/4 " sloped roof per sq. inch of spout. Insofar as gutters, I don t recall the Revere book or Copper Sense mentioning it, however, w/ standard sizes choice pretty limited.>>>

All it has to do is get the water to the ground; and hey, it will eventually get there all by itself! Normally every 40 feet needs a downspout, and the longer the rafters, the bigger the downspout. If the gutters are pitched to the downspout, that will also help get the water to the ground better too.

Have a nice day.>>>