Gutter Fall Ratio

The fall is the measurement by which the gutter drops to allow water to drain towards the outlet downpipes.

Gutter fall ratio.

Box gutter with rain water head at end of box gutter. The minimum gutter fall to a downpipe is 1 500 meaning an extra 2mm of fall for each metre of gutter. The amount of collected water increases until it spills over the sides of the gutter. Before buying talk with your supplier to ensure the gutter system you have selected meets the criteria.

Your gutters must comply with national plumbing and drainage code as nzs 3500 3 2003 which you can find in your local library. If the length of the gutter is 10 5 metres 35 feet the amount of slope required is 1 25 cm 1 4 inch multiplied by 1 metres 3 5 feet which when rounded up is 2 5 cm 1 inch. Calculate the gutter slope by dividing the length of the gutter needed by 10. If gutters don t slope water gathers in them.

The gutter slope also called the pitch is the amount the gutter tilts down to let rainwater flow out of it. Gradient 0 30 24. The standard is about inch per 10 feet. Many plumbers guidelines recommend a ratio of around 1 500 which is roughly 20mm for every 5m of guttering.

As with gutters a downspout s capacity must match or exceed the expected runoff. Through the screw mounting hole in each bracket drill a 3 16 inch diameter hole in the front edge of the gutter. I also had a problem that my new flat roofed loft conversion dumps so much water into the valley on the front roof slope that it formed a fast flowing stream that jumped over the gutter. According to bs 6229 bs 8217 flat roofs should be designed with minimum falls of 1 40 to ensure a finished fall of 1 80 can be achieved allowing for any inaccuracies in the construction.

This can be converted into a gradient written as a ratio or 1. For example is a 24 metre section of drainage pipe has a fall of 0 30 metres calculate the gradient. The above recommendations assume that you have properly sized downspouts every 40 feet. With the steeper fall i now have the water departs the gutters much more rapidly effectively increasing the capacity.

A gradient may be defined as fall divided by distance. Secure the gutter to the bracket with a 1 inch long 8 32 stainless steel machine screw and flanged nut. Gradient fall distance. If gutters slope too severely they don t hold water and water could splash over the sides in heavy rain.

Simplified suitable for flattish roofs with little or no vertical faces or steep roofs draining to one side of box gutter only or any roof if you are in a hurry and make the necessary allowances for all catchments. Increasing the pitch increases a gutter s handling capacity but the gutter may look askew over a long run.