Corrugated iron gutters for rainwater harvesting
This question comes from someone who has been working in Uganda where he has put in plastic gutters and bio-sand water filters made in Uganda in Kampala for $50 but is now looking for some info for a school that is going to collect rainwater using more substantial guttering from galvanised sheet metal or corrugated iron gutter. What advice do we have?
I would like to see any information or examples of corrugated iron gutters as it seems like a viable proposal.
Also, we would like to confirm from others :-
1. is 26 gauge thick enough for V-gutters in
intense rainfall areas
2. if we use V-gutters, what should be the spacing of supports
3.
What is appropriate sealing material/method for joining gutter sections
3 Answers
The book Rainwater Catchment Systems for Domestic Supply by John Gould and Erik Nissen-Petersen, Practical Action Publishing, it contains information on V-shaped metal gutters, U-shaped metal gutters and V-shaped wooden gutters. I didn’t see anything about using corrugated sheet for the gutter. There is a section at the back of the book called “Making and Installing Gutters with a Splash Guard” which has a few photos and states that “V-shaped gutters are made on the construction site by the builders. Galvanised-iron sheets, gauge 26 and 190 x 200cm are cut into strips 33.3cm wide”.
Have you seen our technical briefs on the subject? https://practicalaction.org/rainwater-harvesting-answers
Have you looked at the manual "Roofwater Harvesting" by T.H Thomas and D.B. Martinson? It can be downloaded here: https://www.irc.nl/page/37471
There is a chapter on guttering and using galvanised sheet metal as a material for guttering is discussed on page 109. It states the following:
"Galvanised iron roof sheeting can be cut and bent unto a ‘U’ to form a gutter. A more popular shape, though not one to make best use of the metal area, is a cut-strip folded to give a trapezoidal gutter with a vertical back face to fit against the fascia board and an outwards-angled front face intended to intercept even the most intense run-off.
Unfortunately, the cutting of both curved and of folded gutters leaves a dangerously sharp edge, which is also prone to rusting. Normal tinsmith practice would be to fold over such edges and this is widely done. However, roofing-grade GI sheeting is too hard for this operation and softer metal (milder steel) sheet must be used, which is normally more expensive. Metal gutters made in this way are not easy to support or to join. The gutter-to-gutter joint often leaks unless sealed with some sort of mastic (e.g. bitumen) and taped firmly together (e.g. with rubber strips cut from car or lorry inner tubes). Soldering is another widely used process to join GI gutter lengths, attach end plates or, more commonly, attach metal downpipes to gutters. Such rigid gutter-to-downpipe connections are a source of weakness and one often sees gutters badly twisted because the attached downpipe has moved."
If the harvested rainwater is to be used for potable purposes (drinking), I would avoid the use of bitumen as a join sealant on water quality grounds (https://dwi.defra.gov.uk/drinking-water-products/faqs/FAQ9.pdf). Most of the potentially toxic hydrocarbons leached from bitumen would not be removed by your biosand filters.
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