Rainwater Harvesting and Recycling Made Simple

Saturday, September 16, 2017

Beyond The Water Butt – Reduce Your Water Bill by Recycling Rainwater

Historically man has been catching rainwater and recycling it for millennia. There are early examples from Egypt and Roman times. Some are more complex than others, but the simple message is: catch the water falling from the sky and use it later.

In most countries nowadays health and safety concerns mean that recycled rainwater may not be used as drinking water. Its uses are limited to flushing toilets, washing clothes and watering the garden. There are many parts of the world where rainwater is regularly used as drinking water (also known as ‘potable water’) especially where there is no public water supply, or no other available sources such as rivers or lakes. It is important to adhere to your national and local water regulations. The rest of this article relates to using recycled rainwater for flushing toilets, supplying clothes washing machines and watering the garden.

Because these three areas account for about 50% of domestic water usage, householders can make substantial savings ion their water bills by harvesting and recycling rainwater. Toilets are by far the biggest user of water, with around a third of all water used in a house going straight down the pan.

Most countries have rainfall data which is obtained from regional weather stations. Typically records will detail the average monthly rainfall for the last thirty years. Like weather-forecasting in general, rainfall prediction is a very imprecise science.

In the UK, for example, we know it rains more on the west side of the country than the east, and that Scotland enjoys more rainfall than England. If you are considering installing a rainwater recycling tank it is worth obtaining the average rainfall data from the Meteorological Office because most manufacturers will be using them.

The important facts that you need to establish are:

How large is the roof area from which you will be collecting water?

You must base your calculations upon the flat area and not the pitched area. The Meteorological Office data will tell you how much water will fall in an average year on one square metre of your roof. Multiply these two numbers and then divide by twelve for a rough guide to the monthly rainfall that you will be able to collect in your rainwater harvesting tank. The amount of rainfall will determine the size of tank that you need.

How many people will use the rainwater?

In an average house, a normal person uses around 140 litres per person per day. If you are using harvested rainwater for flushing toilets, washing clothes and watering the garden, this will equate to 50% of your rainwater usage. As a guide, you should work out your water requirements for 14 days, since it is very rare in the UK for 14 days to go by with no rain. If this total is less than the tank size detailed above, then you have a big enough tank. If it is greater, then you may simply not have enough roof space or too many people in the house. Ultimately it is the roof area that determines the amount of rainwater that you can harvest.

Do you need mains water back-up?

If you are using the rainwater recycling system for flushing toilets then, yes, you do. If it is just for garden use, then the choice is yours. Please note that if you have mains water back-up, then hose pipe bans will apply to you.

There are three types of mains water back-up; all are activated when you run out of harvested rainwater.

The first back-up system delivers 100 to 200 litres of mains water into your tank whenever it runs out of rainwater. The second version requires a header tank which stores the back-up mains water; the latter remains within the pumping system. The header tank frequently includes a built-in pump. Mains water is only used when there is not enough rainwater. Electricity is required to power the pump. The third version uses a header tank in the roof space. The rainwater is pumped up to the header tank and usage is by gravity feed. When the rainwater runs out, mains water is fed to the header tank as needed. This system has the advantage of working even when there is no power.

Recycling rainwater to reduce mains water usage is simple and easy. If you are building a new property, you will make the property more attractive by including a rainwater harvesting system. If you have an existing property, then it may be possible to use harvested rainwater for the toilets, depending on where the cisterns and pipe work are situated.

To summarise, simply choose a tank and pumping system, get it installed and start saving on your usage of valuable mains water. You can now see that the systems are simple and easy to understand. And they are easy to install.

Rainwater recycling information is provided by Property and Energy Services as part of our campaign to make renewable energy and environmentally friendly products easy for you to understand and use.

Ian Lloyd

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