The Complete Guide to Rainwater Harvesting

Let’s be honest, rainwater harvesting can sound like a bit of an absurd concept in the UK. It rains at least half the year and it’s not like we have the severe summer droughts of the Australian outback.

Yet even if it does seem a little silly there are some very good reasons to install a rainwater system, even here in the UK.

For example, water bills are rising to extortionate amounts. Earlier this year the government’s water regulator approved a 2% price rise on water, which could add as much as £395 to a yearly bill. Add to that the chronic leakage issues of our national water network and the increasing number of droughts we’re seeing across the UK; consequently it’s not unreasonable to foresee the price only going one way, up.

Additionally, the UK’s population is growing rapidly each year and fresh water is essential for life. The sheer immense pressure that will be put on an already short supply will only increase, and if you take pleasure in gardening or simply enjoy a long, refreshing shower, then rainwater harvesting may be a cost effective and environmentally friendly system to have in place.

What are the advantages of Rainwater Harvesting?

Specifically speaking, rainwater harvesting is the practice of collecting rainwater from surfaces such as roofs, gardens and flooded areas before then storing and filtering the water to make it suitable for human consumption or utilisation.

In 2017, water that can be utilised for human benefit is often in short supply, with expensive man-made resources such as dams and reservoirs required to meet demand. Aside from saving the amount of water you get from the nation’s supplies, what are the other advantages of rainwater harvesting?

Rainwater is Considered Safer than Water from Domestic Mains

Not only has water been stored in dams for long periods of time, but the water through your mains is treated with a variety of chemicals in order to eliminate any bacteria that may be present.

Rainwater Harvesting Systems Can Help Tackle Flooding

The impact of flooding can also be lessened by installing rainwater harvesting systems. During heavy rainfall, storm drains can sometimes struggle to cope with the sheer amount of water trying to escape. The extra run-off facility of harvesting systems can help to ease that burden and reduce the damage that flooding can cause.

Rainwater Harvesting is Cost Effective

Rainwater harvesting can save you serious dollar. Rainwater harvesting systems require only a minimal cost to maintain and once you have it set up correctly, the only thing you will you need to consider is the huge reduction in water bills.

Saving the Environment One Drop at a Time

Save money and save the environment? Is it possible? With a rainwater harvesting system not only can you avoid paying massive water bills, but you can also avoid the environmental damage caused by having the water pumped to your home.

Avoid the Hosepipe Ban

Another summer, another hosepipe ban. After working hard all spring to get your garden blooming, you don’t want to let all your hard work go to waste with a hosepipe ban. Stored rainwater can be perfect solution to stop you falling foul of summer watering bans rules.

How to Harvest Rainwater

Although a standard plastic tank is usually sufficient to store water for use in watering nearby plants, if the harvested water is intended to be used indoors or in large gardens, you will need to invest in a suitable pump system that can be incorporated into your home’s plumbing system.

At its most simple and complex, all rainwater harvesting systems will be made up of the same basic components.

Catchment Area

A catchment area, as you might expect from the name, is an area that is typically designed or altered to collect water. Usually this area will be the roof of your home as the system can be adapted to easily draw water from your home’s drainage system. In more complex systems, you can also collect water from gardens and flooded areas on your property.

Conveyance System

This is just a fancy term used to cover the eavestroughs, downspouts and piping that will be put in place to deliver water from the catchment area to the storage system.

Storage System

Again, as you might expect from the name, the storage system is simply a barrel, cistern or a tank that can hold rainwater for future use.

Distribution System

After you’ve collected the water in your storage system you will need to be able to get the water from its storage place to where it is being used. The manual labour method can be a good start for small gardens, but if you want the water to be fully integrated with your home, then you will need to invest in a pump that can be fully installed to run in harmony with your existing plumbing system.

4 Things to Consider Before Purchasing a Rainwater Harvesting System

Rainwater harvesting systems can be purchased in all shapes and sizes. When considering what system you may need for your home, there are a number of questions to reflect on.

1. How Do You Plan to Use the Water?

How you intend to use the water will be the biggest factor in what system you decide to purchase. Are you simply looking to utilise harvested water in the garden during the summer, or do you need to fully integrate the system into your home for toilet and showering use? How you plan to use the water will require a different set up and, consequently, come at a different cost.

2. How Much Water Do You Need?

Similar to the first question, you need to consider how much water you intend to use. A retired couple looking to utilise harvested water in the garden will need a different system to a family of six who intend to integrate the system with their home’s plumbing. Think about your household water habits, the number of people in your house and if the current plumbing fixtures installed in your home are water efficient.

3. How Much Water Can You Collect?

So you may have an idea of how much water you need, but how much water can you realistically collect? The calculation is simply based on the square feet of your catchment area and average rainfall in your region. Theoretically if you have a catchment area of 100 square feet and receive around 800mm of rainfall annually, then you can collect up to 25,000 litres per year.

The calculation looks like this:

Square Feet of Property

divided by (÷)

3.2

times by (x)

Annual Rainfall

You can estimate how much rainfall you receive annually using Met Office data here: http://www.metoffice.gov.uk/climate/uk/regional-climates

To be even more precise with this figure you would deduct about 20% of the total to account for water that is lost to overflow, evaporation and leaks.

4. How Much Water Can You Store

It is important you estimate how much water you can possibly collect. As mentioned, all rainwater harvesting systems come in different shapes and sizes. Tanks and cisterns can have limited storage capacity. If you purchase a system capacity unsuitable for your region you will need to install an overflow pipe that leads water away from your home. Excess water flooding from a harvesting system can damage your property and foundations.

Deciding on Your Type of Rainwater Harvesting System

After you have answered the four questions above, you can then decide what type of rainwater harvesting system you need for your home. While there are a variety of systems that vary in complexity and size, these can often be covered in three basic models.

Water Butt Systems

The simplest of all rainwater harvesting systems, the water butt is a large plastic container which is connected to one drain pipe. These are great for small scale harvesting and are often the optimal system for people looking to reduce water consumption from their mains when gardening.

The benefit of this system is that you can install the water butt yourself and get harvesting straight away at minimal cost. Remember that if you are purchasing a water butt system you need to calculate how much rainfall you expect to receive. You may need to install an overflow pipe or purchase a larger container if you are expecting large amounts of rainfall (I.e. in an area of the UK that receives particularly high percentages of rainfall all year round).

Gravity Feed Systems

The water butt can be a great system to trial rainwater harvesting, but if you want to ramp things up and reduce your reliance on the mains a step further, then you will want a more complex rainwater harvesting system. The first system to consider is a gravity feed system. These are systems that collect water on the roof of your property when it rains and feed the water directly into the filter system of the tank.

The benefit of this system is that you can harvest large amounts of water directly into your home using gravity. This avoids the costs and complexity of integrating with a power source to pump the water around your home. The downsides of this system are that you may lose a large percentage of your harvest potential by only collecting at roof height and you will need to hire a professional fitter to ensure your system is safe and stable.

Pump Feed Systems

Gravity is great and we will thank Sir Isaac for his discovery for many years to come, but if you want to make a professional job out of your rainwater harvesting system then you will require a pump feed system. With the tank at ground level, or even under the ground, you can maximise the amount of water you harvest before using a pump system to move the water around your home.

The benefit of this system is that the pumps, like the KSB Hya-Rain, can clean and filter the water for you, ensuring that you are receiving a clean source of water. These systems also maximise your harvest potential by connecting to large underground tanks. The only potential downside to this system is the initial set up cost, but once you have the initial sting out of the way, you will recoup the costs when paying reduced water bills.