Collecting rainwater – four things to know!

Having your own supply of water is one of the important steps of self sufficiency.   Water to drink.  Water for animals.  Water for plants.  Water for washing etc etc.

Some people live in areas with abundant water – a running stream, a pristine lake or a great well.   For others, they are collecting rainwater to meet their needs.   I think that collecting rainwater is a something everyone should consider – even the non-homesteaders – to best utilize our natural resources.

So here are some things you need to consider if you plan on collecting rainwater:

1.  Is it legal?
In some places on our globe collecting rainwater is ILLEGAL.   This could be for two reasons.  The first is that all the water in an area may be already owned through a historic system of water rights.  So water falling on your land may already have an owner!   The second reason is that the local building codes do not allow you to install a holding tank. In my lifetime I have lived in places with these laws…but I am happy to say that the second one is being over turned in many places.

Still, before you start collecting rain water, check with your local authorities.

Here is a link to the US states that have some form of collecting rainwater laws.

2. What can you store it in?
Most people use tanks or barrels to store rainwater. These can be placed close to the house or barn and can vary in size from a small bucket to tanks that hold 45,000 liters (12,000 gal). Some people even have tanks made onsite that hold far more than this, especially in desert areas where they need to capture and store every drop from every precipitation event.

A large water tank…with its outlet tap clearly marked for its use!

Australia has some of the best places for getting water tanks.  See the Tankworld website as one example.

In the USA – here are some examples of rain tank suppliers:


Rainwater HOG

The Tank Depot  (and there are many more…)

An alternative is to have an earthen pond or dam for collecting rainwater. These can be used to collect surface water (water running over the surface when it rains) or rain water that falls on the roof of a house or barn and is then piped to the pond.

Here is a great article on the construction of a pond.

 3. Is the water clean?
Water collected from a building roof and directed into tanks can be very clean and ready to drink. However contamination can occur to the water as it passes over roof material. What is the roof made from? Is there any heavy metals in the material such as lead? You can purchase water testing kits or collect a sample and have it tested to find out if you have any issues.

Here is a fantastic summary on a rain water collecting system, and what step you can take to make sure you are safely using the system.

More common an issue is dust, leaves and other debris collects on a roof after a long period between rain events which then washes into the tanks when it rains. Many modern setups have a sediment trap system that diverts the first amount of water running through the pipes flushing this material away before water enters the tank. Old systems rely on using the tank itself as a settling column, with the silt sinking to the bottom of the tank. The tank outlet is then higher than the bottom of tank so you draw water from above the silt layer. In these tanks the silt needs to be cleaned up ever few years.
In past designs, the only way to clean out the material that settled on the bottom of the tank was to climb inside the tank and manually scoop it out. After some very sad accidents when people become overwhelmed by gases in the tanks, new designs started to emerge, including flush valves. Good modern tanks now have a flush valve positioned at the base of the tank so the settled materials can be flushed out every few months.

Here is an article on how to make sure your water is clean and safe to drink.

4. Do you have enough head?
Water flows downhill due to gravity. The greater the height that water has to flow down then the greater the pressure that the water has. If you are just collecting rainwater in a tank and intend to go out and fill up a jug from the tank tap, then all you need to consider is that the tap is high enough to fit your jug underneath. However, if you want to pipe the water into your house and have more than just a trickle of water coming through the pipes, then understanding hydraulic head or pressure is more important.

There is a whole pile of math related to working out the hydraulic head of water in a tank (see here), but the most important thing to know is that to get good pressure into pipes you either need to force the water into pipes using a pump with a pressure tank, or have the water collected and stored at a height above your home.  This means having water tanks raised up on a platform, or the tank situated on higher ground than the house.  A happy compromise that some people use is to have a trickle pump (a pump that pumps at a slow speed) that takes water from a collecting tank near their house/barn and pumps it up to a tank on a hill higher than the house.  The pump runs either all day, or just part of the day (perfect for a solar powered pump) and slowly tops up the upper tank.  When the faucet/ tap is opened in the house, then the water falls under gravity into the house pipes with pressure.  The amount of pressure is based on the hight from which the water falls from the tank to the house.

If you want to use rainwater for you garden using a hose, then you will need to have a considerable pressure, especially if you are using a sprinkler.  For drip systems, you can have much lower pressure.   So based on your use, you may need to really consider a pump.

Here is an article on what option is the best way to go – pumps or pressure tanks.

So if you consider these things before collecting rainwater you should be able to work out a system that is best for you.   It will always depend on what your need for the water is of course – if it is just for drinking, or if you want to pipe it into your house, barn or garden.

We hoped this article was useful.  You may also find the following useful:

Hard water vs soft water

Groundwater wells on your farm

Using Google Earth to map farm zonesTagged on: collectingrainwater