Thatched Roofs - How to Collect Rainwater From Them?

Subject: Collection of rainwater from thatched roofs
Date: Mon, 22 May 2000
From: Art Ludwig <Oasis Design>
To: genusloci <genusloci©>
CC: Joakim Ho <jho©>

Genusloci wrote:
> I am a recently qualified architect and I am at the moment trying to design
> a rainwater storage system to be used in rural Ireland. This will involve
> the collection of RW from thatched roofs, I am sure this is feasible but I
> do not know the runoff coefficient to employ and will the thatch effect
> the water quality? If it isn't too much trouble and if you know the answer
> to these questions can you let me know or put me in touch with someone who
> has done some research in this area? Thank you kindly for your time, Mick.

Wide gutters made from sections of corrugated galvanized steel are used to
catch runoff from thatched roofs in the tropics: functional, but ugly.
Your runoff coefficient might be 0.6 or so instead of the 0.8 usually used.
The quality will certainly be poorer; full of thatch bits and possibly a
dark tannin tea as well. I have oak trees over my roof and they create such
a strong oak leaf tea that you can only see a few feet into the water.
Thatch probably isn't any worse than leaves. Since I use the water for
toilet flushing, washing dark clothes and in the yard this is not a concern
in my application.
A screen filter is a hassle to maintain but will help get those bits out.
Either way, I suggest you design the storage tank to achieve maximum
filtration by floating and settling, like a septic tank, with an outlet
suspended from a float 20 cm below the surface.
A roof washer would be great, but they are especially problematic in
freezing climates.

IT publications is where we're sending people until our book is done. Check out
"Rainwater Catchment Systems for Domestic Supply", ISBN 1-85339-456-4 and
"Rainwater Harvesting" 0-946688-22-2.

Good luck!