Rainwater Collection System

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Although we have access to the community water system that brings water from a small dam in the watershed high on the mountain about 7 kilometers away, we wanted to test the concept of rainwater collection.  We are glad we did, because often the water pressure in our tap to the community system is too low to be useful.  Sometimes the water is cut off altogether for days at a time.  Furthermore, the water in the community system is frequently cloudy with sediment.  Sometimes there is too much chlorine in the water, and sometimes there is none.  Our rainwater collection system gives us crystal-clear, potable water all the time at pressures that vary between 15 and 45 psi. 

The roofs on all three of our buildings are guttered, with downspouts that direct the water to a single 6-inch pipe that dumps the water into a ferrocement collection tank.  At the top of each downspout, there is a screen to prevent leaves and other debris from entering.
 

At the top of the collection tank there is a “T” with another filter screen where the water enters the tank.  The cap on this “T” is held on with screws and can be removed to clean the filter screen.
 

Between the collection tank and the storage tank there is a 400-liter plastic tank filled with sand.  It is called a “biosand filter” because a biofilm of beneficial microorganisms that kill human parasites and pathogens forms in the top layer of sand.  Therefore, we get biological filtering as well as the mechanical filtering by the sand, making it unnecessary to further treat the water.

The water exiting the biosand filter can be directed to one of two ferrocement storage tanks.  The large (30,000-liter) tank is the storage tank, and the smaller (10,000-liter) tank next to it is the reserve storage tank to be used when the large storage needs to be closed for cleaning or repairs or in the case of a severe water shortage. 

The outflow from each storage tank is directed to a small pump house where there is a 3.5 gallon-per-minute diaphragm pump that pumps the water up to a surge tank next to the house. 

We have a homemade solar water heater, and most of the time it is capable of keeping the water sufficiently hot.  The water is circulated through the water heater by convection without the need of a pump. 

Occasionally for a comfortable shower, we find it necessary to use a demand LPG water heater mounted on the wall outside the bathroom. 
 

All of the water from the house drains (the kitchen sink, the basin in the bathroom, the utility sink in the bathroom, the washing machine, the shower, and the urinal) flows by gravity to a 100-liter septic tank downhill from the kitchen.  The purpose of the septic tank is to allow solids to settle and to allow anaerobic fermentation.  

From the septic tank the water flows to a distribution pipe at one end of a long gravel/sand filter in which water-tolerant plants are growing.  (Here the Nitrobacter and Nitrosomonas growing in the root zone convert ammonia to nitrite and then to nitrate.)  Solids that did not settle in the septic tank are removed by filtration through the gravel and sand.  The first filter that we installed lasted 10 years before we noticed that the water flow had decreased to the point where we had to change the sand. 

The nutrient-rich solution that exits the sand filter flows down hill to a 400-liter plastic tank, from which it feeds a drip irrigation system in our orchard.   

Rainwater is collected from the roof of the shop through four funnels in the corners and directed to a ferrocement tank in a separate, independent system that irrigates the vegetable garden and nursery.