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Rainwater harvesting: How saving water could save you money

Rainwater harvesting is used by households around the country, and quite simply collects any rainwater, usually from the roof of a house. This water can then be used to flush toilets, supply washing machines, and hydrate plants. The only place the water can’t be used is in sinks and showers, as the untreated rainwater may eventually be ingested. This reuse of water reduces the need of using water directly from the mains, minimising the pressure on your conventional water supply, and cutting the costs of your water bill. Here we’ll go through exactly how rainwater harvesting works, and how you can implement it within your own home.


What are rainwater harvesting systems?

There are 133 days of rain or snow per year on average in the UK, giving a total of 885 millimetres of annual precipitation. By collecting the rain that falls around a home, you can build up a reservoir of water ready to be used around the house, rather than relying on the mains supply. These rainwater harvesting systems work by using plastic rain butts to collect the water from the guttering pipes around your home, which can either be stored above or below ground.

Storing your water butt below ground helps to regulate the temperature, minimising the risk of evaporated water. Underground water butts also tend to have a filtration system in place, providing cleaner water for your home, which only needs to be checked about once a year. However, they are much more expensive to install, as there needs to be an excavation in order to make room to bury the system underground, and underground pipes will need to be fitted, which will drive up the cost, and disrupt your garden.

Storing your water butt above ground is much easier to maintain, and can be easily installed in your home as part of a DIY project. However, you run the risk of dealing with leaves or even flies falling into the water butt if the lid is not secured on. The heat during the summer months can also encourage evaporation, and potentially cause the water to turn smelly, or freeze over in the winter months. However if the collected water is used regularly, these problems can generally be avoided. At Water Butts Direct, we have a range of rainwater harvesting systems that can be either wall mounted, or free-standing. We also offer a range of designs, allowing you to turn your water into more of a feature piece for your garden.


How big should a rainwater harvesting system be?

Getting the right size rainwater harvesting system depends on what you’ll be using the water for, and how much you’ll realistically need. As a general rule of thumb, 5% of the available annual rainfall is a good starting point for the storage capacity. A water butt that holds between 1,500—2,000 litres will supply the water for toilets and washing machines of the average UK household, however you will need to keep in mind how much rainwater you’ll be collecting, and how often you’ll be using the water.

To work out how much water you can collect from your property, you need to determine how much water falls on your home. This is essentially the area of the roof on your property plan, which is similar to the size of the ground floor. You then need to find out the expected annual rainfall in your area, which you can check on the Met Office website. Simply calculate the available water by multiplying the average rainfall with the area of your roof. Bear in mind that only around 80% of this water will actually be collected, as much of the water will fall onto the ground, or may not be heavy enough to fall into the guttering in order to be collected. Some rainfall can even be lost to evaporation, as well as overflow (when there is too much water already in the water butt), which you should also take into consideration.

You should also consider incorporating a filtration system, which can remove any small contaminants such as dust, leaves, and other organic waste that may be swept into the water butt from your gutter, into your rainwater harvesting system. This makes it much easier to use directly around the house, and you won’t need to worry about removing this unwanted debris when you go to collect the water, or while it’s being pumped back into your house.


What can rainwater be used for around the house?

In the average household, around 30% of the water is used to flush toilets, which is considered wasteful due to the purification process that water undergoes before it hits a residential property. The average person can use up to 34.5 litres flushing their toilet every day, which can quickly mount up, especially in a household. Using a rainwater harvesting system to flush toilets can be massively beneficial for saving water, as well as saving money on your bills. If you’re going to use rainwater for this, ensure you have a water butt large enough to hold enough water to be economically worth it, and that the water is connected to your toilet for easy flushing.

You can also use rainwater to keep your garden and plants watered. This is particularly helpful during a heatwave, when the government may impose a hosepipe ban. The water collected in a rainwater harvesting system is free to use, and isn’t included as part of a hosepipe ban, so can be easily used to ensure your plants are kept healthy, and don’t dry out, without using treated water that is fit for human consumption. Rainwater can also be much healthier for gardening purposes, as it doesn’t contain the chemicals included in the treating of water. Simply connect your hose pipe directly to your water butt, or fill up your watering can, saving you money in water costs.

If you’ve connected your water butt to your household plumbing, you could use it to power your washing machine. Washing machines use around 50 litres of water per wash on an average cycle, which can be easily substituted for your free supply of rainwater. Rainwater is also useful when washing clothes, as it is naturally soft, eliminating the need for fabric conditioner. The soft water can also reduce the buildup of limescale, prolonging the life of your machine and reducing the risks of it working inefficiently. You simply need to add a filtration system to your rainwater harvest system, and have it connected to the plumbing for your washing machine, replacing the main water supply. Switching to rainwater for your washing machine can act as a significant saving to your water bill, as it is one of the main domestic uses of water that doesn’t actually require treating.

The soft rainwater can also be used for general cleaning surfaces around the house, such as windows and cars. This is because there are no added chemicals to the water, which tend to result in spots and streaks across the glass, provided they are scrubbed well enough. Simply collect and filter the rainwater, and use it to clean your windows and your car while cutting the amount of purified water used from your main water supply.

Explore our collection of water tanks for rainwater harvesting here.


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