2.3 Roof and Gutters: Designing Gutters
Calculating gutter width and length between downspouts for semicircular, box, V, or trapezoid gutters made of any building material
For those of you that will design or install your own gutters, this link will open another powerful spreadsheet that will help you design a gutter, and determine how far you can go between downspouts.
DOWNLOAD: Designing Gutters Spreadsheet
Note: The file is an Excel spreadsheet and will require that you have this program installed locally to use it. Your computer (depending on the browser you use) should give you the option of saving the file locally or simply opening it. If you accidentally started changing the yellow box values, simply close the spreadsheet without saving and reopen.
For some of you, designing gutters will be left to an installer. They are perfectly capable of designing a successful system. I would suggest that you ask them to install the gutters at a ¼-degree slope for the first 2/3 of the gutter length before the downspout, and an angle of ½-degree for the last 1/3 of gutter length. This will get the water flow fast enough to help move debris along and help prevent the pooling which can draw insects, biota, and increase corrosion
Congratulations, you have just finished one of the most difficult tasks in rainwater harvesting; deciding on a tank, and gutter size and location.