The short answer
Yes, gutters and downpipes can feed a water butt or a larger harvesting tank, usually through a diverter fitted into the downpipe. A butt for the garden is a simple fitting; a tank that supplies the house is a plumbing and drainage project. In both cases the gutter, fall and downpipe need to be in good order, and the overflow must go safely to a drain or soakaway.
How a water butt connects to a downpipe
The simplest set-up is a diverter. A section of the downpipe is cut away and a fitting is inserted that sends water into a hose or pipe leading to the butt. When the butt is full, the diverter lets the water carry on down the pipe to the drain as before. Some diverters are fitted into a hopper or a rainwater pipe boot, while others are clipped on with a short flexible tube.
The butt sits on a firm, level stand so that a watering can fits under the tap. A full butt is heavy, so the base needs to be solid. A lid keeps out leaves, light and insects, and a mesh at the inlet keeps out debris. Overflow is the part people forget, and it matters most: a butt without an overflow will spill against the wall in a heavy downpour.
Before cutting any pipe, check what kind of pipe you have. Plastic downpipe is easy to work with, while cast iron needs a different approach and may be part of a listed or conservation area building. Our guide to downpipes and drainage on Stroud homes explains how the pipe connects to the drain below.
Larger systems that serve the house
A harvesting tank is a step up from a butt. A tank is often buried or placed in a plant space, is fed by a filter on the downpipe or a gutter-run collector, and sends water to garden taps or to the house for toilet flushing and the washing machine. The pump, filter and pipework make it a plumbing job, and a system that links to the mains supply has its own rules to protect drinking water, which a plumber or specialist installer should confirm.
Do not take on connecting harvested water into the house plumbing as a do-it-yourself job. Ask the installer to explain how the system meets requirements and which approvals apply, and speak to your building control body if you are unsure. We cannot offer legal advice on this page.
Where a tank is buried, the ground works and the overflow route become the biggest part of the project. The overflow needs a route to a drain or soakaway that can cope, because a full tank in a storm sends all the water it cannot hold to the overflow pipe.
What the gutter has to do first
A butt is only as good as the water arriving. If the gutter holds standing water, leaks at the joints or overflows at a corner, much of the rain never reaches the downpipe. Fixing the fall comes first. Manufacturers typically recommend a gentle slope towards the outlet, roughly 1:600 to 1:350 depending on the system, as covered in our answer on what fall a gutter should have.
Debris is the second concern. Whatever lands on the roof ends up in the gutter and then in the butt: moss, grit, bird droppings and leaf litter. Clear the gutter regularly, and fit a leaf strainer or a filter at the inlet so the butt does not turn into a sump. Water from the roof is fine for watering plants but not suitable for drinking.
Roof coverings matter a little too. Run-off from moss treatments, and from some paints and metal, can harm plants or fish, so avoid collecting water straight after treating a roof. A fascia that has rotted behind the gutter will let it drop, so see our answer on capping over old fascias before assuming the boards are sound.
Weight, brackets and the extra load on the roofline
A butt takes water from the downpipe but does not add weight to the gutter. A diverter, though, changes how water moves through the pipe, and a blocked inlet can back water into the channel. If the diverter is fitted high up on a downpipe, check that the pipe clips are secure.
If the gutter feeds a larger collector, the whole run needs to be sound. Bracket spacing is set by the maker; FloPlast gives a maximum of 500mm for its MiniFlo range, and Brett Martin gives 900mm or less. Any gutter that sags or has loose brackets is a poor starting point for a harvesting scheme.
Scaffold and access have a cost. MyBuilder's 2026 roofline price guide puts scaffold at £20 to £40 per m² and guttering at £30 to £70 per metre. If new gutters are going on anyway, that is the best moment to add outlets or alter the downpipe position, since the access is already in place.
Planning the job and getting it priced
Start by deciding what you want the water for. A butt for the garden needs a diverter, a stand and an overflow. A tank for the house needs a design, an installer and approvals. Choose the downpipe that serves the largest roof area and sits nearest to where the water will be used, and make sure the overflow route is clear.
If you live in a listed building or a conservation area, changes to the front of the house, including pipework, can need consent. Listed buildings carry full legal protection, so ask Stroud District Council's planning team before altering a visible downpipe, and choose a rear or side elevation where you can.
On the roofline side we look at gutters, outlets, downpipes and fixings, and the quote covers scaffold, labour and materials, with VAT stated. A photograph of the downpipe and the ground beside it, sent by WhatsApp or the form on this page, is enough to start. Part of our guttering, soffits and fascias work, it carries a 10-year workmanship guarantee in writing.