The homeowner’s guide to garden rainwater harvesting

The impact of climate change has meant summers of higher temperatures, less rainfall, and more frequent hosepipe bans. In turn, we all need to think more carefully about water as a resource and how it’s managed.

The less water you take from a mains tap, the less taken from reservoirs, which consist of 80% river water and 20% groundwater. That’s good for both the environment and your water bills. Rainwater harvesting is an easy way for homeowners to collect and store water for later use. It helps to reduce the strain on water supplies in dry periods.

Read on to learn more about harvesting rainwater and why it’s such an easy thing to do.

This article covers the water butts that can be installed outside your property. Underground harvesting systems are available too. However, they’re much harder to install and usually require planning permission.

What is rainwater harvesting?

Rainwater harvesting is an eco-friendly and sustainable way to collect rainwater. It’s especially useful in the summer when hosepipe bans are common. Rain is stored in a tank known as a water butt. A range of sizes are available based on water usage needs and the space available. Rainwater harvesting systems are typically placed where they’ll collect the most rainwater.

You can use the collected rainwater for watering your plants and lawn, and for washing your car without having to use the mains.

How does rainwater harvesting work?

When rainwater drains from your roof, into gutters and downpipes, it usually ends up either in a soakaway, or the main sewage system. It’s then treated at water treatment plants, then fed back into rivers and seas.

A rainwater harvesting system collects rainwater flowing into downpipes. Once the tank is full, an overflow valve diverts excess water into the normal drainage system . Most of these tanks have taps at the base, so you can fill a watering can or bucket, or attach a garden hose.

What are the benefits of rainwater harvesting?

You’ll conserve water, and you could save money

According to OFWAT, the process of collecting, treating and supplying clean water to the mains contributes towards climate change. In addition, Energy Saving Trust reports that an increasing number of water suppliers are operating in water stressed areas, one of which is the South East. Harvesting rainwater lets you reduce the amount of water used from your local water company, and in turn, you could save money on your water bills.

It’s better for your plants

Many people water their plants from the mains supply, but gardeners in the know will usually advise against this. That’s because drinking water from your kitchen tap has already been treated with chemicals to make it safe for us to drink. These chemicals are fine for human consumption but plants prefer rainwater.

An alternative water source during hosepipe bans

Dry summers can lead to hosepipe bans, as water companies try to conserve their supplies in times of drought. If you break this ban and use a hose to water your garden, wash your car or fill a child’s paddling pool from the mains, you could get a fine of £1,000. In contrast, hosepipes can be connected to rainwater harvesting tanks, as long as these tanks have been topped up with natural rainwater.

Can I drink harvested rainwater?

No, you shouldn’t try to drink the harvested water that’s kept in outside storage tanks. Unlike what comes from your main water supply, the rain stored in your tank isn’t considered ‘potable water’, which means it’s unsuitable for drinking or food preparation. Rainwater can collect bacteria while it travels across the roof and through the gutters, and this affects the water quality.

Important! We can put a sign on the tank to make it clear that people shouldn’t drink from it, and install a child lock for complete peace of mind.

How do I maintain my rainwater harvesting system?

1. Check the water tank intermittently

Inspect the tank for damage and make sure the lid is securely fastened. If it isn’t, you may find mosquitos start to breed. We recommend visually checking the water intermittently to make sure you’re happy with the water quality.

2. Clean the tank each year

It’s recommended that you clean the tank once a year by emptying it out and scrubbing it down with warm water and detergent. As a form of preventative maintenance, you can buy water butt cleaning solutions that prevent the growth of scum and algae, and keep the system smelling fresh. We recommend doing this at the end of the summer when the water in the tank is likely to be at a low level.

3. Use the collected water regularly

In the summer, you’ll probably be using your rainwater harvesting system a lot. At other times, it may fill up and sit unused for days at a time. By using water you harvest frequently, you prevent it from stagnating.

4. Get a roofer to check the gutters and downspout

Gutters, the downpipe, and the pipe connected to the storage butt can all clog up with leaves and other debris. Our roofers can check these annually when you book with us for gutter cleaning.

How much does a rainwater harvesting system cost?

How much you pay to harvest rainwater depends on the size and number of water butts you need. Heavy duty tanks that are more durable cost more. Domestic rainwater harvesting tanks typically hold between 100 and 300 litres. An entry level models with a diverter costs around £50.

An Aspect roofer can help to install it for you. They’ll connect the tank to your existing downpipe and check that your gutters and connected fascia boards are in good condition. If you want to harvest rainwater from a roof that doesn’t have gutters, such as a garden room, or garage, we can install these for you.

You also need to think about a solid base for the water butt to sit on, as it’s going to be very heavy when it’s full of water. It’s important there’s no risk of it falling over.

If you’re using a cast iron downpipe, we may need to install a uPVC replacement. If you already have one made of uPVC, then the install will be quicker. Installation usually takes between 2-3 hours, assuming you already have a solid base for the water butt to sit on.

Is rainwater harvesting legal in my area?

Garden rainwater harvesting systems in the UK are legal, but they must comply with the Water Supply (Water Fittings) Regulations 1999. This act governs the quality of the installation work and ensures it’s not set up to be used for drinking water.