Here at Friendly Organics we love anything that helps sustainability and reduces the pressures on vital resources such as water. We have worked with quite a few institutes and homes on how to harvest and store rain water for use in the dryer months.
Many people go with the simple solution of using barrels or similar vessels to store rain water, using the down pipes from the roof as a collection method. However, what many do not consider is how they will get the rain water from the receptacle to their plants. Of course, some simply attach a tap to the bottom and fill a watering can, this is fine if you only need one or two watering cans of water.
If your water requirements are more than a couple of watering cans then you might want to connect your water receptacles to an irrigation system, either new or existing. It is very easy to plan for water collection, its cleanliness, and installing the collection/distribution system but then fail to consider the actual movement of the collected rain water.
Even one barrel collecting rainwater is a marvellous idea, it’s affordable, practical, and periods of longish droughts an ideal short-term alternative to using city water.
Before we consider the means to transport your harvested rain water let’s consider what type of barrel or another receptacle you will need. Ideally you need a barrel with innards made from dense polyethylene, this will give longevity to your barrel. Many rain barrels will have a polyethylene core and wood/metal exterior for visual appeal and personal style. You should aim to install the largest barrel you can and at least 50 gallons. This stores more water and can increase the water pressure to transport to your garden. You will be amazed at how quickly funnelling rain water from your roof will fill up a 50 gallon barrel.
If you have decided that you want to go down the irrigation route you could install a submersible water pump within your barrel, depending on gradient and distance. However, if you are considering using gravity to transport your lovely harvested rain water then some math is involved.
Now math is not my speciality, so I have researched the internet and found this equation.
A water level 2.31 feet above its exit point will produce 1 PSI (pounds per square inch). This means the level of the water inside of your barrel has to be 2.31 feet above the irrigation system which it supplies to generate just 1 PSI.
An average garden watering system need at least 10 PSI.
For consistent, stable water pressure that meets your garden’s watering needs (e.g. to create 10 PSI), the water level of your barrel needs to be 23.1 feet above the garden and higher for additional pressure or larger irrigation systems.
If you want a sufficient water pressure from a rain barrel (without using a pump), your barrel’s water level needs to be 23.1 feet above your garden. You can now see why many people opt for the water pump, which can be solar powered.
Let’s end on a positive and consider some positives of installing rain barrel(s). On the island when long droughts are experienced water restrictions are often put in place, having your own stored rain water could preserve your garden.