Collecting, storing and reusing water

Rainwater is the best option for garden watering. It is naturally soft, low in minerals and has the right pH

This describes how acid or alkaline soil is, and is expressed as a number between 0 and 14. Soil with a pH of 7 is neutral, an acid soil has a lower value, and an alkaline soil has a higher one. Most plants grow best in soil that’s within a specific pH range, so it’s useful to know your soil’s pH. Testing kits are easy to use and widely available in garden centres and online. for most plants, including acid-lovers like rhododendrons and camellias. The minerals found in mains water, especially in hard water areas, can raise the pH of soil and affect nutrient availability.

Collecting rainwater in water butts is a great way to decrease reliance on mains water and can help reduce flooding during heavy rainfall. Collect water from the roof of your house, garage, greenhouse or shed. Roofs with a decent pitch and a relatively clean surface are ideal for ensuring the rainwater you collect is as clean as possible. If you are short of space or need to disguise your water butt, slimline and decorative models are available.

• You’ll need a gutter with a downpipe or a rainwater downpipe kit
• A filter will prevent leaves and debris from entering the water butt
• Place water butts on firm, level stands (which you can buy) or bricks, so you can fit a watering can beneath the tap
• Join multiple water butts together with connector kits or siphons
• You can connect a hose to the tap of a water butt, but for good water pressure you will need a submersible or external pump
• Cover the water butt with a close-fitting lid to prevent rain-borne spores of plant diseases from entering the water butt, and to discourage algal growth

Linking slimline water butts allows you to collect and store more rainwater where space is limited

Dipping tanks

These are troughs usually connected to a downpipe from a roof. They often contain pond plants and can be stylish versions of the traditional water butt, though their lack of a cover can be a potential issue, as uncovered water can stagnate and harbour harmful micro-organisms.  Avoid using water from dipping tanks for watering seedlings

A seedling is a young plant grown from seed. and young plants.

Can I use water butt water on all my plants?

Use rainwater stored in water butts on established plants

Established plants have been in their current location for two or three years and so have well-developed root systems able to support strong growth with healthy foliage and flowers. , but avoid using it on seedlings because it may contain damping-off diseases. Rainwater is also perfect for watering your houseplants, particularly orchids and carnivorous plants.

Do water butts need to be cleaned regularly?

Yes, clean water butts annually to prevent disease build-up and smells. Use warm water and a little washing up liquid. 

How to minimise risks to people:

• Use a coarse spray setting on hoses connected to water butts so droplets are less likely to be breathed in. Breathing in water droplets from stagnant, warm water can pose a health risk
• When hoses are not in use, disconnect them and let them drain 

How to minimise risks to plants:

• Keep gutters clear to prevent organic debris from entering stored water. This will reduce risks of waterborne plant diseases such as Phytophthora and Pythium
• Use stored water frequently to keep it fresh
• If the water smells, empty and clean the water butt rather than adding chemicals
• Rainwater collected in dipping tanks can contain pathogens such as Phytophthora, Pythium, Rhizoctonia and Fusarium. Keeping gutters and tanks clean helps reduce the risk 

As the climate changes and there are drier summers but more winter rain, it may be practical to install a rainwater harvesting system to support plant growth in the hotter months. Some systems include underground storage tanks. The UK Water Reuse Association website contains information on rainwater harvesting systems.

Grey water is water from showers, baths, washing machine rinse cycles and kitchen sinks. Recycling household water for use as grey water can be very useful during water shortages. To use it safely, bear in mind the following:

• Avoid water containing bleach, disinfectants, dishwasher salt, or harsh cleaners
• Use grey water immediately – do not store it longer than 24 hours unless filtered through a reed bed, sand filter or a professionally designed water treatment system
• Apply using a watering can; grease and fibres can clog irrigation systems
• Alternate with rainwater or mains water to avoid mineral salt build-up in soil
• Ideally, only use grey water on ornamental plants, rather than edible crops. If you do use grey water on edible crops, limit it to crops that will be cooked (so don’t use it on salads, for example)

Grey water from washing up can be used to water ornamental plants in containers

Softened water comes from water that has had calcium and magnesium removed and replaced with sodium ions.

Yes, it’s good for short-term use, but in the longer term, it is not recommended. Sodium can build up in soil, which can reduce the availability of critical plant nutrients, adversely impact the health of plants at very high levels, and can also affect the structure of the soil. 

Boiling water removes bacteria. In hard water areas some of the calcium will be removed during the boiling process but generally not enough to make it ideal for plants that need soft water. 

Water from dehumidifiers or tumble dryers is condensed and therefore suitable for use on many ornamental plants. Orchids, carnivorous and other plants that need soft water will benefit from rainwater or condensed water. 

Purified water, such as distilled or deionised water, contains almost no dissolved minerals. It is too expensive for widescale use but can be helpful for plants that need very soft water, such as orchids, when rainwater is unavailable. However, because purified water lacks minerals, fertilisers need to be added to meet plants' nutrient needs. Some orchid specialists use their own deionising or reverse‑ osmosis

Osmosis is the movement of water molecules from an area of high concentration (where they are abundant) to an area of low concentration (where they are less so) through a semi-permeable membrane. This process is vital for the survival and growth of plants. systems, but most people would have to source purified water from car accessory or aquatic shops. For most gardeners, the cost, transport and storage issues make purified water an unrealistic option.