Rainwater Harvesting PVC piping
PVC pipes for collecting rainwater became brittle and out of use after two and a half years. Could this - apparently - accelerated aging be caused by excess UV radiation or is it more likely due to the quality of the pipes (made in Ivory Coast). Any other suggestions or remedies, e.g. taping the replacement pipes? Julien Smets
Could be either/both, UV will cause PVC to become brittle, and often local PVC pipe is very thin. You can try painting the PVC pipe, at least where it will be in sunlight. If you see a gray colored PVC pipe that tends to be a little more UV resistant.
The aging of the pipes is indeed likely to be due to UV light. You could try specifying UV stabilisied pipes (a pigment is added to feedstock that absorbs UV) or a different pipe material. Depending on costs you may have to accept that there will be a limited design life to plastic pipes in this application. In the past I have used sun shades for plastic tanks, but this is unlikely to feasible or cost effective for guttering. The other alternative would be to make gutters from a more durable material, e.g corrugated sheets or split bamboo.
Painting PVC is somewhat difficult as the smooth surface does not allow the paint to stick very well, and inside where the water runs it will likely be washed off very quickly.
Generally speaking PVC pipes are not meant to be used being exposed to the sun, but using darker materials (called "emerald" here in the Philippines) and thicker walling (again here in the Philippines you can get "600" or "1000" type of pipes, with the latter significantly thicker) will probably help a bit.
But using specifically made plastic gutters from LDPE or similar will be always the better option as it is much more resistant to UV light.
Regarding non-plastic materials: yes you can use galvanized sheets and often already pre-bend profiles for gutters are available, but also there you need to take care of the thickness and due to the common riveting, you end up with something not much more duable as it will start rusting at the rivets very quickly. Of course you can solder it, or cover the rivets with silicone or special paint, but overall it becomes quite complicated and costly to construct if it is supposed to last more than a few years.
Another thing you have to keep more in mind with other types of materials is thermal expansion that will be more pronounced with material less flexible than plastics (again the rivets and connection points can be an issue there).
And last but not least, heavier and often sharp edged metal gutters will become a serious flying hazard when ripped off in a storm as is likely going to happen after some time of rusting.
This thread is public, all members of KnowledgePoint can read this page.