A 100mm of rain falling on a typical UK semi-detached roof — say, 60 square metres of shed-and-extension downpipes alone — produces around 6,000 litres of runoff. Most of it goes straight down a soakaway. A water butt catches some of it and gives it back over the dry weeks of June and July when you actually need it.
For a small UK garden, a water butt is one of the highest-return purchases you can make. It pays for itself in a single hosepipe-ban summer, it makes raised-bed watering practical without trekking buckets from the kitchen tap, and it’s roughly a Saturday morning’s job to install. The trick is buying the right one — and most of the “best water butt” lists either over-recommend 350-litre barrels that don’t fit small gardens or under-recommend slimline kits that turn out to be missing the diverter you need to actually plumb them in.
What size do you actually need?
The instinct is to buy the biggest barrel that fits. The right answer is more nuanced.
For a small UK garden — a paved courtyard, a five-by-five back lawn, or a passageway down the side of a terrace — somewhere between 100 and 250 litres is usually right. Less than 100 litres and you’ll empty it in two waterings of a vegetable bed. More than 250 litres and the footprint starts taking up disproportionate space, and you’ll find the bottom 30% of capacity rarely gets used because by the time you’ve drawn that much water, fresh rain has refilled the top.
The exception is greenhouse and allotment growers, who can usefully run 350-litre barrels because their water demand spikes in summer. For everyone else, a slimline 100–250 litre butt sited at the busiest downpipe is the right answer.
What you actually need to buy (the bit most lists skip)
A water butt on its own is not a complete installation. You need:
- The butt itself.
- A stand. Tap clearance for a watering can. Some kits include this; many don’t. Without a stand, you’ll end up with a butt sitting directly on the ground and a tap you can only fit a flat tray under.
- A diverter (filler) kit. Connects the downpipe to the butt and — crucially — diverts the flow back into the main downpipe once the butt is full, so it doesn’t simply overflow over your patio. UK standard downpipes are 68mm round or 65mm square; most diverters fit both.
- A tap. Some butts come pre-fitted; some come with a tap to install yourself; some come with neither.
Read the listing carefully. A “100L Water Butt Set” often includes butt, lid, tap, stand and diverter. A “100L Water Butt” often includes only the butt and lid. The difference is a budget-tier outlay of accessories you’ll have to buy separately.
Recommended water butts for small UK gardens
1. The slimline default — Strata 100L Slimline Water Butt Set
The most-bought water butt in this category in the UK, and deservedly. The Strata 100L slimline is a 100-litre butt with a roughly 38 × 53cm rectangular footprint — slim enough to fit down the side passage of a terrace, against a fence, or behind a shed. A complete kit version includes the stand and diverter; the bare butt is also widely available if you already have those.
Setting it up takes around 15 minutes once you’ve levelled the ground. Cut the downpipe at the height of the diverter, slot in the diverter, drill a hole in the butt at the diverter outlet height, and connect. The diverter handles both 68mm round and 65mm square downpipes — the UK standard — but check yours isn’t an older non-standard size before ordering.
View Strata 100L Slimline Water Butt Set options on Amazon
Best for: Small gardens, side passages of terraces, and anyone wanting a complete kit at the budget end.
Trade-offs: The basic plastic finish looks like what it is. The legs of the stand can be slightly wobbly until the butt fills.
2. The capacity upgrade — Strata 250L Slimline
If you have wall space for it, the same Strata slimline format scales up to 250 litres in a footprint that’s only marginally bigger — roughly 60 × 60cm. Square-shaped, sits flush against a wall, and gives you a serious capacity uplift for a small additional footprint.
Note that some 250L Strata variants ship with butt-and-tap-and-lid only; the stand and diverter are sold separately. The fully kitted version is the one to buy if you’re starting from scratch.
Check Strata 250L Slimline Water Butt with Stand and Diverter price on Amazon
Best for: Slightly larger small gardens, growers with greenhouses, and anyone who’d rather spend once and have plenty of capacity.
Trade-offs: Black plastic in a square shape. Not pretty.
3. The traditional barrel — Harcostar 168L or 227L
For a more traditional aesthetic, the Harcostar barrel-shaped butts are made in the UK from recycled plastic, have a child-safe lockable lid, and come in 114, 168, 227, and 350-litre sizes. The 168L sits in the right capacity range for a small garden and looks more like a “proper” water butt — the kind your grandparents had — than a flat slimline.
The 227L is a step up that will fit in most reasonably-sized small gardens. Both come with a Universal Rain Trap diverter that handles 63, 68, 80, and 100mm round or 61 and 65mm square downpipes.
See Harcostar 168L Water Butt with Stand and Diverter on Amazon
Best for: Traditional and cottage-style gardens, growers who want a known-quality UK-made butt, and anyone whose downpipe isn’t the standard 68mm round.
Trade-offs: Round footprint takes more floor area than slimline equivalents.
4. The wall-mounted option — for genuinely tiny spaces
If you have a balcony, a tiny concrete courtyard, or a side passage so narrow that even a slimline butt won’t fit, wall-mounted water butts in the 100-litre range exist. They’re more expensive per litre than a freestanding butt, the diverter installation is fiddlier (you need to land the diverter at the right height for the butt’s inlet rather than the other way round), and they need a wall structure that can take the weight of 100kg of water on a bracket.
For most small UK gardens, the slimline ground-level butt is a better answer than the wall-mounted option. But if you genuinely have nowhere else, this is the format. Look for kits that include the wall brackets and diverter rather than buying components separately.
Compare Wall-mounted Garden Water Butt 100L options on Amazon
Best for: Balconies, micro-courtyards, and side returns under 30cm wide.
Trade-offs: Higher cost, fiddly install, and you must verify the wall can take the load.
5. The decorative option — Sankey Beehive or planter-top water butts
If you want a water butt that doesn’t look like a black plastic box, the Sankey Beehive (150L), Stewart Garden oak-effect butts, and various planter-top butts (where the lid is a shallow planting tray) exist. They sit at a clear premium over equivalent-capacity plain plastic butts of similar capacity.
Honest position: for most small-garden buyers, this is paying for aesthetics, not function. If aesthetics matter — front gardens, visible patios, anywhere the butt is in eyeline — they earn their price. If the butt is going down a side passage no one sees, the Strata slimline is the better answer.
View Sankey Beehive 150L Water Butt options on Amazon
Best for: Front gardens, visible patios, and growers who’d rather pay more than look at black plastic.
Trade-offs: Premium pricing for what is functionally the same product.
At-a-glance comparison
| Butt | Capacity | Footprint | Includes | Best for |
|---|---|---|---|---|
| Strata 100L Slimline Set | 100L | 38 × 53cm | Butt, stand, diverter | Side passages, small gardens |
| Strata 250L Slimline | 250L | ~60 × 60cm | Varies — check listing | Larger small gardens |
| Harcostar 168L | 168L | Round, ~55cm dia. | Butt, stand, diverter | Traditional aesthetic |
| Wall-mounted 100L | 100L | Wall-fixed | Brackets, diverter | Balconies, micro-spaces |
| Sankey Beehive 150L | 150L | Round, decorative | Butt, lid | Front gardens, visible patios |
Buyer checklist before you click
- Confirm the listing includes the stand and diverter, or budget separately for them
- Check your downpipe size — UK standard is 68mm round or 65mm square; older properties may have non-standard
- Pick a flat siting location and check it before ordering — a butt rocking on uneven ground gets unstable quickly when full
- For child or pet households, confirm the lid is lockable
- If the butt will get direct sun, look for UV-stable plastic (most modern butts are; some budget imports aren’t)
- Buy the stand the manufacturer designed for the butt, not a generic — height matters for tap clearance
Setting up a small-garden water butt
Pair the butt with the busiest downpipe — usually the kitchen extension or main back roof. The shed downpipe is tempting but typically catches a fraction of the rain and the butt sits empty most of the year.
Make sure the ground is level. A water butt is heavy when full (a 100L butt weighs over 100kg with water in it) and even a small lean makes it unstable. A slab or two of paving on top of compacted ground is enough; a proper concrete pad is overkill for small-garden capacities.
Site it close to your raised beds if possible. Walking 15 metres back and forth with a watering can in July gets old quickly.
FAQ
How much water does a water butt actually save me?
A 100L butt that fills and empties twice a week through a UK summer will save somewhere in the order of 1,000–2,000 litres a year — modest in absolute terms, but enough to matter during a hosepipe ban, and enough to keep raised beds going through dry spells without using mains.
Will the water go off?
Stored rainwater is fine for garden use indefinitely. It can grow algae if exposed to direct sun without a lid (which is why butts come with lids), and standing water can attract mosquitoes (which is why lids should be sealed). It is not drinking water and shouldn’t be used for anything you’d drink.
Can I link two water butts together?
Yes — most slimline butts have linking points pre-marked, and linking kits are sold separately. Two linked 100L butts give you 200L of capacity in a slightly distributed footprint, which can be a better fit than a single large butt.
Do I need to drain it in winter?
In most of the UK, no — water butts are designed to handle freezing and the lid prevents catastrophic ice expansion. In Scotland and exposed northern locations where temperatures fall well below freezing for sustained periods, leaving the tap slightly open over hard frost windows reduces stress on the plastic.
Do I need to clean the butt?
Once a year is plenty for most small-garden butts. Drain it, scrape any sediment from the bottom, rinse, and refill. Algal treatments are sold but not really necessary if the lid is on properly.
Is it worth getting a butt with a planter on top?
Functionally no. Aesthetically, sometimes. The planter on top adds modest utility for a clear premium over a plain butt of equivalent capacity.
Last reviewed: April 2026. Product availability and pricing on Amazon.co.uk change frequently — check current options before buying.