Planning sustainable water solutions for smart homes

Setting up smart sustainable water collection, storage and filtration systems for a smart sustainable home

Water is a highly valued commodity despite the fact that our entire planet is covered in it. Changes in global climate are driving changes in the way we manage resources. Modern technology also makes it easier to develop small scale smart home sustainable water systems that rival commercial infrastructure from decades past. There has also been a failure of governments to keep up with changes in a variety of areas. This makes it necessary for us to become smarter about how we manage the resources we need to sustain life.

Rain Collection

The first most obvious way of obtaining water is from rain and the key is to maximise the collection areas. A house roof is the first easiest place to start with planning for the collection of rain water. Having an angled roof will help to channel the water down to the lowest point where it can be further directed for storage or use. There is also the surface area of other buildings or the land itself if collection channels are dug out. You can also choose to simply position stormwater collection drains at strategic points around the property.

Understanding how much surface is available for collection makes it easy to determine how much can be collected. There are some simple calculations that can be used to determine this. The first calculation is just determining the surface area of any collection areas. A house roof that is 15 x 8 metres (48.21 x 26.24 feet) is 120 square metres (394 square feet).

Rainfall is measured in millimetres and According to weather scientists one millimetre of rain is equal to one litre per square metre.

So if there is 120 square meters of collection area this will collect 120 litres of water for every one millimetre of rain. Knowing how much you can collect combined with how much you use will determine a reasonable amount of storage. The average usage per person according to the New South Wales State government in 2016 was 340 litres per day.

First Flush

Before channeling water into storage containers it’s important to ensure that debris is removed. This starts the cleaning process and ensures the quality of the water. A first flush system allows larger debris to be captured first and separated from stored water. The dirty water gets captured and when it fills the system and then blocks off and directs the rest to storage.


Determining appropriate amounts of water storage is a matter of determining how far off the grid you want to go. If we use an average of 300 litres daily and multiply by 365 days that’s 109,500 litres per person annually. Depending on where you live and how often it rains will determine how much storage to have. Every month that’s 9,125 litres per person. If you have a collection capacity of 120 square metres then this is 120 litres of water for every 1mm of rain. In order to store one months worth of water for one person based on these numbers you only need 77mm of rain.

How much water storage is appropriate depends on your goals and what you can manage with the resources you have. You may want to be fully self sufficient or you may just want to take care of your gardening needs. It’s up to the individual needs. If you have a family of four then this is potentially 40,000 litres per month. If you live on a property then a water-well may be a viable option to supplement the water supply.

Some areas are experiencing less rainfall than in previous decades due to changes in the climate. This means that larger water storage capacity is necessary. One way to determine some basic needs will be to determine the local areas average rain fall. If the average rainfall is 90mm per month than on a 120 square meter collection capacity will allow for 10,800 litres of water to be collected on average per month. That’s enough for one persons personal use.

Filtration & Purification

In order to make water safe for human consumption it needs to be treated. The natural water cycle on earth has methods of doing this that we can emulate in a setup. It’s important to know what things are in water that can be harmful to humans. These include dirt and debris as well as biological and viral contaminants.

There are several methods for cleaning water to make it safe for consumption. Boiling, Filtration and Disinfection are recommended by the Centres for Disease Control as methods that may remove some or all contaminants. Setting up a system that incorporates all of these before delivery is key to making the water as safe as possible.

There are natural filters and man made filters. The CDC recommends filters as narrow as 0.3 of a micron to filter bacterial contaminants at their smallest. This is not a guaranteed solution but just part of an overall system. Iodine or chlorine are recommended as methods of disinfection or chlorine dioxide.

There is a three stage DIY filtration system that is commonly shown in YouTube videos. They consist of a layer of gravel, a layer of sand and a layer of activated carbon. This also works as a scalable system as it is a replica of part of the natural water cycle.

Delivery Methods

Once you’ve collected, stored and cleaned the water ready for use then there is getting it to where it’s needed. 

Gravity Feed

Gravity Fed is one of the oldest methods and was used by the Greeks and the Romans. It is estimated that for every one meter of height there is 0.1 bar or 1.45 psi of pressure. This means that 10 meters of height is going to create 1 bar or 14.5 pounds per square inch of pressure. This is the equal to 1 atmosphere of pressure. One bar is the amount of pressure necessary to raise water through pipes to the height of 10 meters.

As a point of reference a household tap will have anywhere from 45psi to 80psi as a standard and in Australia a flow rate of 9 Litres per minute has become the maximum standard. Where as a high pressure hose for cleaning a driveway or a fence will generally be anywhere from 1500 to 2000psi.

To obtain the required pressure for a household system would require a water storage system to be raised from 31 meters to 55 meters above the end point. This is not viable option for a home setup however using a gravity fed system to deliver water to key locations may be an option.

Motorised Pump

Motorised pumps are easy to come by for various purposes. They can be obtained from hardware stores or plumbing supplies. The first thing to determine is what specifications the pump needs to meet in order to do the required job. This will be determined by factors such as the distance the water needs to travel, the elevation, of the final destination from the source the size of the pipe being used the demand pressure and the friction loss of the pipe. These can be calculated using pipe friction tables and pump flow rate charts combined with the physical requirements of the delivery system like a sprinkler or hose head.

There’s a lot involved however the trick is to take each part of the system and break it down into steps to put together.

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