Setting up your rainwater harvesting system may sound intimidating. However, it can be done by anyone who wishes to conserve water. But before we setup our rainwater harvesting system, let’s emphasize the importance of planning for the project. There are a few things that we have to consider before doing the work.
What are rainwater catchments for?
To begin planning for our rainwater catchment system, we must identify the objectives we intend to achieve in setting it up. This helps us determine certain requirements. Do we collect rainwater for solely watering the plants in our backyard? Do we intend to save up water in doing laundry? How about drinking water? What about the size of the tanks to be used? Will a simple rooftop catchment system suffice? Will I need help from a professional? Answering such questions will help us identify its complexity and how our rainwater catchment system is designed.
How big should your rainwater catchment water tank be?
There are two important factors that we have to consider in identifying the suitable water tank capacity.
The Climate
As a rule of thumb, if an area receives frequent rain throughout the year, fewer and smaller tanks will suffice. Smaller tanks are refilled more often due to the recurring rains. For areas that are dry and has a distinct rainy season, rainwater should be collected as much as possible to last until the next one. Hence, bigger water tanks.
The amount of Rain and the Roof Surface Area.
The Roof or catchment area can be a factor in determining the capacity of our rainwater tanks. This capacity can be computed by the following formula:
Harvested water (Liters) = Catchment Area (sq. m) x Rainfall depth (mm)
Where to setup rainwater catchment water tanks
It is ideal to set-up tanks near the downspout as it provides easy filling. However, it may not always be feasible because of the layout of your property and the size of your tank. If the tank is placed a little farther away from the downspout, downward sloping runs of gutter or pipes can be used to distribute rainwater from the roof. Water tanks should also be placed on a sturdy and level base.
Proper tank elevation for smaller tanks
Smaller tanks are often elevated. This is done for two purposes:
The tap and spigot are located below the tank. An elevated tank provides a clearance for watering cans or containers during filling.
When water is heavy and exerts weight, it eventually pushes itself down. This is called the Head Pressure. The amount of head pressure depends on how large, how tall and how high the tank is. Smaller water tanks cannot exude the same amount of head pressure in filling up containers as much as the big and taller ones if tanks directly sit on the ground. This can be a problem when connecting hoses as the water will have to go upwards while the head pressure cannot fight off the gravity which pulls the water down.
It’s essential to explore every question for every project, let alone a simple rainwater catchment system. It helps us avoid mistakes and wasted efforts while maximizing the results we intend to gain. Articulating objectives and requirements as well as determining water tank capacity, location and elevation are few steps that we take for a hassle-free rainwater harvesting installation in our homes.
References:
Average rainfall, ideal tank size and roof surface area. . (n.d.). Retrieved March 13, 2021, from Rain Harvesting by BlueMountain Co. : https://rainharvesting.com.au/4-pillars-of-rain-harvesting-system-design/understanding-your-needs/average-rainfall-ideal-tank-size-and-roof-surface-area/
Rainwater Collection Systems 101 & FAQs. (2019, December 5). Retrieved March 13, 2021, from Homestead and Chill : https://homesteadandchill.com/rainwater-collection-systems-101/
WaterCare. (n.d.). Retrieved March 13, 2021, from watercare.com.ph : http://watercare.com.ph/rainwater.html