How to calculate whether we need an additional downpipe?

Sebastian90

Hey folks,

I'm redoing my Mum's gutters, and I'm wondering if I need another down pipe? The two green dots near corners "H" and "A" are the only current two, and the red "x" in a box on corner "D" is where water has pooled and rusted through the gutter. Any advice? In South Australia, if that effects codes.

 

MitchellMc

Welcome to the Bunnings Workshop community @Sebastian90. It's wonderful to have you join us, and many thanks for your question about installing gutters.

I'm of the understanding that there are two main regulations that must be adhered to regarding your question: A minimum fall for eave gutters of 1:500, so for every 500cm, it must drop 1cm, and downpipes must not serve more than 12m of gutter. As an approximation based on your lineal meterage of guttering, you would be required to have five downpipes. I'm not a drainage specialist, but I've had a crack at selecting the location for those downpipes in the image below. The only downpipe that would not strictly adhere to the 12m rule would be location H with 14.1 m heading to it. 

In answer to your question, you would definitely need another downpipe at D, as that whole area of gutter isn't adequately serviced.

Before going ahead with this work, it would be worth checking with your local building authority to determine if this work needs to be carried out by a licensed professional, as is the case in some parts of Australia.

Please let me know if you have any questions.

Mitchell