Making a novel rainwater collector
Most rainwater collection systems use roofs to collect water. These offer a convenient and relatively large surface area exposed to the sky. The writer has used a roof on his house for some years to collect rainwater for domestic use. The shade cloth gutter described elsewhere on this site has been in use for about 5 years and still operates. Every year it must be cleaned out, as leaves and dust accumulate during the dry season. Also the early rains must be allowed to go to waste as the roof itself will have become dirty and must be flushed down.
As an alternative to this conventional method of collecting water from the roof, the writer experimented during the 2004/5 rainy season with a collector which looked like an inverted umbrella.
The inverted umbrella rainwater collector
This consists of an umbrella shaped frame made of polyethylene pipe (25mm) fitted together with polyethylene tee pieces and wire. This is shown in the photo. The diameter of the umbrella in this case is 1.9m, but it could be made larger. A clear plastic sheet large enough to cover the exposed surface was purchased and its corners were attached with string to 4 small weights. A hole was cut in the centre of the plastic sheet and attached with wire to a plastic container filled with stones. This acted as a central weight. During use the plastic sheet is pulled down centrally to form a cone down which the rainwater can run.
During a rainy spell or storm, the inverted umbrella frame is placed over one of two plastic containers (plastic dustbins in this case) each with a capacity of about 90 litres when full. The two containers are connected by a 25mm polyethylene pipe fitted to half a polyethylene socket bonded into the wall of each container. This means that when the container under the collector is full water will flow over into the second container.
Rubber cord or string is used to stabilize the umbrella to the container, which may blow off in a gust of wind. Then the plastic sheet is taken and thrown over the frame with the centre pulled down so the sheet became cone shaped. Once the rains begin fresh rainwater collects immediately.
As the rain falls, the first container fills up and then overflows into the second container. When this is full, or as it fills, water can be taken by bucket to the main cement jar reservoir (for construction details see elsewhere on this site). When the rains have finished water in the first container can be removed by taking off the collector and transferring the water by bucket to the main storage jar. When not in use both containers are covered with lids, the plastic sheet is stored out of the sun and the umbrella also put to one side.
Since the water is completely fresh it can be taken directly by bucket and placed in the larger cement jar. There is no need for any settlement, as is sometimes the case with water taken off the roof.
This method does mean that someone should be at hand when the rains begin. Some rains may be so light that it is not worth putting things in place to collect rain. But on some occasions good rains or even a storm can be anticipated. Then it is certainly worth while to prepare the equipment. Depending on the amount of rain, considerable amounts of water can be collected. During one exceptionally heavy storm on 17th January 2005, 93mm of rainfall led to the collection of nearly a quarter of a cubic metre of water, one quarter of the capacity of the main storage jar.
The two 90 litre plastic containers connected by 25mm plastic pipe. These are actually strong plastic dustbins. On the right the polyethylene pipe frame for the rainwater collector has been placed over one of the containers. It is held in place with rubber cord or string.
The plastic sheet has been placed over the frame. To avoid being blown off by wind it is held down by four weights attached to the corners and a centrally placed plastic jar filled with stones. The plastic is pulled down into a cone shape.
Looking down on to the clean rainwater collecting surface. The lower polyethylene pipes are wired together. Around the rim they are held together with polyethylene tee pieces.
During the rains the first container fills up with water and then overflows into the second container. A bucket is used to carry this fresh rainwater to the main storage vessel which in this case is a one cubic metre ferrocement jar. This is shown in the background.
Water collected in the containers is transferred to the jar via a 30 litre plastic bucket with a stainless steel sieve in the base. This helps to extract leaves and other small particles from the water before it enters the tank.
In this case a tea strainer has been used as a sieve. This is made of fine stainless steel wire, ideal for the purpose. It is fixed to the bucket base with soft putty. Four 4mm holes are drilled to allow the water to pass out of the bucket into the jar. Using this system new water is added to the jar slowly and does not disturb the resting water inside.
The complete rainwater harvesting system.