Installing a water butt is one of the most rewarding weekend projects you can tackle for your garden. Not only does it significantly lower your water bills, but it also provides a continuous supply of untreated, chlorine-free rainwater that your plants will naturally thrive on. Mains tap water often carries dissolved minerals and lime that raise soil pH over time, whereas harvested rainwater is soft and slightly acidic. Setting up a water storage system requires only basic hand tools, a little patience, and a clear understanding of how to link your roof runoff safely into a secure storage barrel.
Whether you are dealing with a compact slimline model tucked beside a shed or a heavy-duty 200-litre barrel against a house wall, the mechanics of installation remain largely identical. This comprehensive guide walks you through every physical step of the job, from choosing the right stable foundation to cutting the downpipe, mounting the rainwater diverter, and managing your overflow safely through the wetter months.
Choosing the Right Water Butt and Stand
Before you lift a hacksaw or measure a downpipe, you need to evaluate your space, roof catchment area, and storage goals. Standard garden water butts range from compact 100-litre slimline configurations designed for narrow side passages to sprawling 250-litre models capable of weathering extended dry spells. A larger roof surface fills barrels rapidly, making larger capacity units or linked multi-barrel setups an intelligent long-term investment.
Equally important is the selection of a solid stand or plinth. Water is exceptionally heavy-one litre equals approximately one kilogram, meaning a standard 200-litre barrel weighs well over 200 kilograms when completely full. Placing a heavy water container directly on soft garden soil will cause it to settle unevenly, potentially toppling the structure or snapping your downpipe connections. A dedicated plastic stand, a stack of concrete blocks, or level paving slabs raised at least 30 centimetres off the ground is mandatory. This elevation creates the necessary gravity head to slide a standard watering can comfortably beneath the outlet tap.
Essential Tools and Materials Checklist
Gathering your equipment beforehand prevents frustrating mid-job trips to the hardware store. Because most suburban homes feature standard plastic guttering, matching your diverter kit to your exact pipe dimensions is critical. British round downpipes typically measure 68mm, while square configurations generally measure 65mm.
- Water butt and matching stand: Ensure the capacity matches your available wall space and catchment potential.
- Rainwater diverter kit: The core mechanism that captures roof runoff and automatically diverts excess water back down the storm drain.
- Hacksaw or fine-toothed hand saw: For making clean, straight cuts through plastic downpipe material.
- Cordless combi drill with hole saw bit: Usually a 25mm to 29mm hole cutter depending on your specific tap and hose inlet specifications.
- Spirit level and tape measure: Vital for checking ground flatness and marking accurate cutting heights.
- Work gloves and safety glasses: Protecting eyes and hands from plastic swarf and sharp cut edges.
- Utility knife or file: For deburring cut pipe ends to guarantee a watertight seal.
Step-by-Step Installation Process
Working methodically through the installation phases ensures a leak-free system that functions reliably for years. Do not rush the measuring phase; accuracy here dictates whether your fittings align smoothly.
1. Position and Level the Base
Clear a flat workspace directly adjacent to your chosen downpipe. Lay your paving slabs, concrete blocks, or purpose-built plastic plinth onto compacted ground. Use your spirit level across multiple directions to verify absolute flatness. Place the empty water butt on top of the stand and rotate it so the threaded drain tap faces outward for effortless access when filling cans.
2. Fit the Drain Tap
Screw the plastic drain tap into the pre-threaded hole at the base of the water butt. If your model features an unthreaded hole, push the tap through from the outside with its rubber washer flush against the container wall, then secure and tighten the locking nut firmly from the inside. Avoid overtightening, as excessive force can warp the plastic threading and create a persistent slow leak.
3. Mark the Rainwater Diverter Height
Hold your rainwater diverter against the downpipe, aligning its internal collection cup roughly level with the inlet hole on the upper side of your water butt. Use a pencil to mark the upper and lower cut lines on the pipe, referencing your specific diverter manufacturer instructions for the exact gap length required. Generally, you will need to remove a 3cm to 5cm section of pipe.
4. Cut and Clean the Downpipe
Put on your safety glasses and gloves. Using your hacksaw, cut squarely through the marked sections of the downpipe. Take your time to keep the cut line perpendicular to the pipe walls. Once the section is removed, use a fine file or utility knife to clean away all plastic burrs and rough edges. Smooth edges ensure that rubber seals inside the diverter slide home cleanly without catching.
5. Install the Diverter and Flexible Hose
Push or click the rainwater diverter into the gap in the downpipe. The internal collection mechanism will capture water running down the inner walls of the upper pipe and channel it through the flexible feeder hose. Drill the inlet hole in the upper side of the water butt if it is not pre-drilled, insert the rubber grommet, and connect the flexible hose securely between the diverter outlet and the barrel.
Advanced Setups: Linking Multiple Water Butts
If your roof surface generates significantly more rainwater than a single barrel can hold, you do not have to let the excess run to waste. Connecting two or more water butts together in a series is a straightforward upgrade that drastically expands your storage capacity without requiring complex plumbing.
To daisy-chain containers, place both water butts side-by-side on identical level stands so their water levels balance evenly. The primary water butt connects directly to your downpipe diverter as normal. Using a hole saw matching your linking kit specifications, drill a matching hole low down on the facing sides of both butts. Insert the threaded bulkhead connectors, apply the rubber sealing washers, and join them with the provided flexible linking hose.
When the primary container fills from the roof runoff, surplus water flows naturally across the low linking pipe into the secondary barrel until both are completely full. Only when the entire combined volume is saturated will the primary diverter initiate its automatic overflow, sending unwanted water down the standard storm drain.
Managing Overflow and Preventing Base Erosion
An overlooked installation detail often involves managing how the system handles maximum capacity. During heavy winter downpours, your water butt will fill and overflow repeatedly. Modern diverter kits solve this gracefully by routing excess volume straight back down the original downpipe once the barrel reaches capacity, eliminating the need for a separate overflow pipe.
However, if you operate an older style top-fed system without a diverter, you must run a dedicated overflow hose from the upper rim of the barrel directly to an exterior drain, gully, or soakaway. Never allow a water butt to discharge water directly onto its own foundation slabs. Uncontrolled runoff softens the ground beneath a 200kg load, causing the plinth to shift, the barrel to lean, and potential structural strain on your downpipe fixtures.
Maintaining Clean Water and Preventing Algae
Stored rainwater remains remarkably fresh for months when managed correctly, but two environmental elements can degrade water quality: sunlight and organic debris. Light exposure encourages algae to bloom, turning clear water green and fouling internal components, while decomposing leaves and roof grit breed bacteria.
Maintaining a pristine system requires only basic preventative habits:
- Keep the lid sealed: An opaque, tightly fitted lid starves algae of the sunlight it requires to photosynthesize and prevents mosquitoes from using the surface as a breeding ground.
- Install gutter guards: Mesh screens over your roof gutters and leaf strainers inside your downpipe prevent moss, twigs, and bird droppings from entering the storage tank.
- Perform annual flushes: Once a year, preferably in late winter before the growing season starts, disconnect the barrel, empty it entirely, and scrub the interior walls with a stiff brush and clean water. Avoid chemical detergents or bleach, as chemical residues will harm your plants.
Winterizing Your Water Butt Against Frost
Water expands by approximately nine percent when freezing into ice, generating immense physical force capable of splitting plastic seams or bowing container walls. Preparing your rainwater system for hard winter frosts protects your investment and ensures it is ready for spring.
Always leave at least a ten per cent air gap at the top of the barrel through freezing periods, giving expanding ice room to push upward rather than outward against the container walls. In regions prone to severe sub-zero temperatures, switch off your diverter mechanism or drain the barrel down halfway. Remember to drain the external tap completely after use during frosty spells, or insulate the spout to prevent trapped water from splitting the valve housing.
By taking the time to build a level foundation, mounting an accurate diverter, and practicing basic seasonal maintenance, your new water butt will supply abundant, mineral-free water to your garden reliably for many years.
