Are Water Butts Really Worth Having?

Can We Store Enough Winter Rain to Survive a Hot, Dry Summer?

We have a 250-litre water butt in the garden. In fact, we have two.

At first glance, 250 litres sounds like a considerable amount of water. It is certainly heavy enough: when full, the water alone weighs approximately a quarter of a tonne. Yet during a hot, dry spell, watering only the plants that genuinely need protecting can empty one of our large water butts in less than a week.

That raises an awkward question.

Are water butts genuinely useful, or do they merely give us a few days of reassurance before running dry?

And if summers such as 2026 become more common, could an ordinary household reasonably collect enough winter rainwater to keep its essential garden plants alive throughout a prolonged drought?

The answer is:

Yes, water butts are worth having—but a conventional 200- or 250-litre butt should be regarded as a short-term reserve, not a complete summer water supply.

To become genuinely drought-resilient, we need to think in thousands of litres rather than hundreds.

The Summer That Exposed the Weakness in Our Water Storage

The summer of 2026 has provided a very practical test of household water resilience.

On 29 July, the Environment Agency declared half of England to be in drought after exceptionally low rainfall and high temperatures. The affected areas included Hertfordshire, London, the Thames Valley, East Anglia, the West Midlands, Wessex, Devon and Cornwall, and Hampshire and the Isle of Wight.

This followed an unusually dry spring. England received only 65% of its average spring rainfall, while southern England received approximately half its normal amount. Some counties in eastern and south-eastern England received little more than one-third of their usual seasonal rainfall.

For gardeners, this has not been an abstract environmental story.

It has meant:

containers drying out within a day;
newly planted shrubs beginning to wilt;
fruit and vegetables needing regular attention;
hanging baskets becoming almost impossible to maintain;
ponds losing water rapidly;
lawns turning brown;
and water butts reaching empty long before meaningful rain arrives.

A water butt works brilliantly when occasional summer showers regularly refill it. It works far less impressively when there is no useful rainfall for several weeks.

What Does 250 Litres Really Mean?

Most gardeners do not measure their water use carefully. We fill a watering can, walk around the garden and return for another. It is surprisingly easy to use ten, twenty or thirty watering cans without noticing how quickly the total is rising.

A standard large watering can holds approximately 10 litres.

Therefore, a 250-litre water butt contains only:

25 full watering cans.

That may sound adequate until we consider the plants competing for them.

A few large containers might each need several litres. A newly planted tree may need 40–60 litres during a dry week. The RHS advises that newly planted trees can require four to six 10-litre watering cans each week in dry weather.

Add tomatoes, courgettes, runner beans, fruit bushes, greenhouse plants and a few vulnerable shrubs, and 250 litres can disappear remarkably quickly.

Our own experience suggests that we are using approximately 35–50 litres per day when concentrating only on important plants.

At that rate:

Stored water	At 35 litres per day	At 50 litres per day
250 litres	About 7 days	5 days
500 litres	About 14 days	10 days
1,000 litres	About 29 days	20 days
2,500 litres	About 71 days	50 days
5,000 litres	About 143 days	100 days

This immediately changes the discussion.

Two 250-litre water butts provide 500 litres. That is useful, but in a demanding dry spell it may supply the garden for only ten days.

For a 90-day period with little useful rain, our estimated requirement would be somewhere between:

3,150 litres at 35 litres per day; and
4,500 litres at 50 litres per day.

That is between 13 and 18 standard 250-litre water butts.

Clearly, lining the entire side of the house with small barrels is not necessarily the most practical answer.

The Surprising Part: Collecting the Water Is Not the Main Problem

It is easy to assume that there may not be enough winter rainfall to fill a large tank.

In most cases, that is not the real problem.

The basic rainfall calculation is straightforward:

One millimetre of rain falling on one square metre produces approximately one litre of water.

Imagine that 50 square metres of roof drains into a rainwater storage system.

A modest 10mm rainfall event could theoretically produce:

50m² × 10mm = 500 litres.

Just one fairly wet day could therefore refill two 250-litre water butts.

Over 100mm of rainfall, the same roof could collect approximately 5,000 litres before allowing for losses caused by splash, filters, gutter overflow and the initial dirty runoff from the roof. Allowing an illustrative 15% loss would still leave about 4,250 litres.

Over an entire autumn and winter, a suitable roof may deliver far more water than the garden could store.

This leads to the real conclusion:

The limiting factor is usually not how much rain falls on the roof. It is how much water we can retain once the rain has fallen.

A 250-litre butt fills, reaches capacity and then sends every additional litre down the drain.

During a wet winter, it may overflow dozens of times. Yet when summer arrives, we still begin with only 250 litres.

We do not necessarily have a rain shortage during winter. We have a storage shortage between winter and summer.

So Are Ordinary Water Butts Still Worth Having?

Absolutely.

Their limitations should not disguise their genuine benefits.

They replace treated drinking water

Rainwater does not need to be extracted, cleaned, treated and pumped to our homes before being poured onto a flower bed. The RHS describes rainwater as an excellent first choice for gardeners where it can be stored.

They are particularly useful for certain plants

Rainwater is generally well suited to ericaceous plants such as blueberries, camellias, azaleas and rhododendrons, especially in hard-water areas.

They capture short summer showers

A brief shower may not penetrate deeply enough to help the plants, but it can put dozens or hundreds of litres back into a connected water butt.

They reduce peak demand

During very hot weather, millions of households may try to water gardens at the same time. Using stored rainwater reduces pressure on treated water supplies.

They make water use visible

A mains tap can feel almost limitless. A water butt has a visible level. As it falls, we naturally become more selective about where the water goes.

They slow rainwater runoff

Capturing water where it falls can reduce the immediate volume entering drains during intense rainfall, especially when storage is connected to an overflow, soakaway or rain garden.

The problem is therefore not that water butts are pointless.

The problem is that we sometimes expect a small water butt to perform the job of a large rainwater harvesting system.

How Much Storage Would Be Sensible?

The right capacity depends on the garden, the roof, the soil and the plants being protected.

250–500 litres: an emergency buffer

This is suitable for:

a small patio;
a handful of pots;
a small greenhouse;
topping up a wildlife pond;
short dry periods;
or reducing ordinary summer tap-water use.

It is not sufficient for maintaining a sizeable garden through a prolonged drought.

1,000 litres: a meaningful reserve

A 1,000-litre tank could provide approximately 20–29 days of water at our estimated rate of use.

This may be enough to bridge shorter dry periods or keep a carefully selected group of plants alive.

A cleaned, food-grade intermediate bulk container—often called an IBC—can provide this capacity, although it needs a solid base, safe fittings, protection from sunlight and careful positioning.

2,500 litres: genuine drought resilience

At 35 litres per day, 2,500 litres could last for around ten weeks. At 50 litres per day, it would last for about seven weeks.

For many households, this may represent a reasonable compromise between resilience, cost and physical space.

5,000 litres: a seasonal garden supply

A 5,000-litre tank could potentially supply our priority watering for 100–143 days.

This begins to approach enough storage to carry essential plants through an unusually dry summer, particularly when combined with efficient watering, mulch and occasional greywater.

However, a full 5,000-litre tank weighs five tonnes. It requires an engineered, level base and cannot simply be placed on a few spare paving slabs.

Do Not Size the Tank Before Measuring the Garden

Before buying more storage, it would be sensible to measure actual water use.

For one or two weeks, record:

how many watering cans are used;
which plants receive water;
how often each area is watered;
whether water is being lost through pot drainage or runoff;
and which plants could survive without watering.

This produces a personal daily water budget.

For example:

Garden requirement	Approximate daily allocation
Greenhouse tomatoes and cucumbers	10 litres
Essential containers	10 litres
Young trees and shrubs, averaged across the week	8 litres
Fruit and vegetables	10 litres
Wildlife and pond top-up	2 litres
Total	40 litres

A 90-day dry-weather reserve at 40 litres per day would require:

40 × 90 = 3,600 litres.

That does not mean the household must immediately install a 3,600-litre tank. It provides a target against which different combinations can be considered.

Perhaps the solution is:

2,500 litres of stored rainwater;
500 litres from linked water butts;
reduced plant demand;
occasional safe use of greywater;
and a small amount of mains water reserved for emergencies.

Decide What Actually Needs Saving

In a drought, trying to keep the entire garden looking as though it has rained every week is unrealistic.

Water should be prioritised.

Highest priority

These are the plants most likely to suffer permanent damage or crop failure:

newly planted trees and shrubs;
young fruit trees;
greenhouse crops;
vegetables at critical flowering or fruiting stages;
seedlings;
plants in pots and hanging baskets;
shallow-rooted plants;
valuable or irreplaceable specimens;
and plants already showing serious stress.

Medium priority

These may need occasional deep watering:

established fruit bushes;
productive vegetable beds;
recently divided perennials;
and established plants with naturally high water demands.

Lowest priority

These can usually be allowed to cope naturally:

established lawns;
mature, appropriately planted shrubs;
established trees;
drought-tolerant perennials;
and ornamental areas that can recover when rain returns.

The RHS recommends allowing established lawns to turn brown, watering only plants that genuinely show signs of need, and applying water deeply at the base rather than repeatedly wetting the surface.

A brown lawn is not necessarily a dead lawn. In many cases, it is simply dormant.

The Cheapest Water Tank Is Better Soil

Installing a larger tank is only half the solution.

The garden itself should become a water-storage system.

Soil rich in organic matter can retain more moisture. A generous mulch reduces evaporation, suppresses weeds and shades the surface. The RHS recommends improving soil with organic matter and applying mulch to help conserve water.

Practical measures include:

Apply a substantial mulch

Place around 5cm of compost, bark, leaf mould or another suitable material around vulnerable plants.

Mulch should be applied over moist soil. Putting dry mulch over already dry ground may make it harder for later light rain to reach the roots.

Water deeply rather than little and often

Frequent surface watering encourages shallow roots. A slower, more substantial watering encourages roots to explore deeper soil.

Create watering basins

A shallow ring or “doughnut” of soil around a tree or thirsty plant prevents water escaping sideways before it soaks in.

Move containers into groups

Grouped containers shade one another and create a slightly more humid local environment.

Use saucers where appropriate

Saucers allow runoff from pots to be reabsorbed rather than lost across paving.

Shade vulnerable pots

A pot standing in direct afternoon sun can heat up dramatically. Moving it into partial shade may reduce its water requirement without harming the plant.

Use larger containers

Small pots have little water reserve. Larger containers dry more slowly and experience less extreme temperature fluctuation.

Install drip irrigation

Drip lines can deliver controlled quantities directly to plant root zones. They are far more targeted than spraying large areas with a hose.

Plant in autumn

Autumn planting allows roots to establish during the wetter months before the first summer drought.

Every litre that remains in the soil is a litre that does not have to be carried from the water tank.

Could Greywater Fill the Gap?

When stored rainwater is exhausted, lightly used household water can provide a useful emergency supply.

Suitable sources may include:

water collected while waiting for a shower to warm;
bathwater;
some shower water;
and suitable washing-machine rinse water.

However, untreated greywater should not normally be stored for more than 24 hours because bacteria can multiply. It is best used by watering can on ornamental plants, avoiding water containing bleach, disinfectants, dishwasher salt or harsh cleaning products. The RHS advises against using untreated greywater on edible crops because of contamination risks.

The easiest form of greywater collection requires no plumbing at all.

A bucket or watering can placed in the shower while the water warms may collect several litres that would otherwise enter the drain. Repeated every day, this can provide a meaningful amount for containers and ornamental plants.

Greywater is not a perfect substitute for rainwater, but it can extend the life of a stored supply.

Practical Ways to Increase Storage

Link the two existing water butts

Ensure both tanks fill evenly and that the connecting pipe is sufficiently large and correctly positioned. A small connection can restrict the transfer rate during heavy rain.

Add storage to several downpipes

One large tank is not the only solution. Smaller tanks can be distributed around sheds, garages, greenhouses and the house.

This also places water closer to where it will be used.

Capture water from outbuildings

A greenhouse, shed, workshop, garage or covered seating area can each provide another collection surface.

A shed roof measuring 12 square metres could collect approximately 120 litres from only 10mm of rain.

Consider a 1,000-litre container

This can be an economical step up, but it should:

previously have contained a safe substance;
be cleaned appropriately;
stand on a firm and level base;
have a secure lid;
be protected against algae-producing sunlight;
and have a controlled overflow.

Install a purpose-made above-ground tank

Larger vertical tanks can hold 1,500–5,000 litres while using less ground area than a row of conventional water butts.

Consider underground storage

An underground tank can preserve garden space and provide very substantial capacity. It is, however, a larger engineering project involving excavation, access, filtration, pumping and safe overflow arrangements.

Use the overflow constructively

When storage is full, excess water can be directed into:

a rain garden;
a swale;
a soakaway;
a wildlife area;
or a well-drained planted border.

The aim should not merely be to store water in plastic containers. It should be to retain more water within the whole garden.

Important Safety and Installation Considerations

Large-scale water storage must be treated seriously.

One litre of water weighs approximately one kilogram.

Therefore:

a 250-litre butt holds about 250kg of water;
a 1,000-litre tank holds about one tonne;
a 2,500-litre tank holds about 2.5 tonnes;
and a 5,000-litre tank holds about five tonnes.

Large tanks require a suitable, stable base. They should not be able to topple, slide or settle unevenly.

Other considerations include:

secure lids to protect children and wildlife;
leaf filters;
mosquito prevention;
accessible cleaning points;
frost protection for taps and exposed pipes;
an overflow capable of handling heavy rainfall;
a means of preventing stagnant debris;
and, where required, a suitable pump.

Rainwater from a garden tank should never be assumed to be drinking water.

Is a Large Tank Financially Worthwhile?

This is a more difficult question.

For a metered household, replacing mains water with several thousand litres of rainwater will reduce the bill. However, 4,000 litres is only four cubic metres of water. Depending on local tariffs, the direct financial saving may be modest compared with the cost of purchasing and installing a large tank.

For an unmetered household, there may be no immediate reduction in the water bill at all.

A large rainwater system should therefore not be judged only through simple financial payback.

Its wider value may include:

keeping valuable plants alive;
maintaining food production;
reducing reliance on mains water;
providing resilience during restrictions;
reducing pressure on rivers and reservoirs;
controlling stormwater runoff;
and preparing the home for hotter, drier summers.

A large tank may make more financial sense when it also supplies toilet flushing, outdoor cleaning or other suitable non-drinking uses throughout the year. That requires a properly designed rainwater harvesting system rather than a simple garden water butt.

What Would I Do Differently?

Our two 250-litre water butts have proved useful. They have supplied hundreds of watering cans with free rainwater and reduced our use of treated mains water.

But the summer of 2026 has also exposed their limitations.

They are buffers, not batteries.

We have installed extensive solar generation and battery storage because we recognise that producing energy is only part of the problem. Energy generated at the wrong time must be stored until it is needed.

Rainwater is exactly the same.

Winter may provide plenty of water, just as a sunny afternoon may provide plenty of electricity. The challenge is moving that resource through time.

If I were redesigning our garden water system, I would think in terms of:

measuring the genuine daily requirement;
reducing that requirement through mulch, soil improvement and better planting;
connecting every useful roof area;
installing several thousand litres of safe storage;
prioritising plants rather than trying to preserve the appearance of the entire garden;
and keeping greywater as an emergency secondary supply.

The objective would not be to make the garden immune to drought.

It would be to give the most important plants a realistic chance of surviving one.

The Final Verdict

Are water butts worth having? Yes. Every suitable home should probably have one.

They collect a valuable resource, reduce demand for drinking-quality water and provide an immediately useful reserve.

But we should be honest about what a 250-litre water butt can achieve.

For a small collection of containers, it may be sufficient. For a substantial garden during a summer such as 2026, it may last less than a week.

If we want to store enough winter rain to survive a long, dry summer, then the answer is technically yes—but it requires a different scale of thinking.

We may need:

1,000 litres for a modest reserve;
2,500 litres for meaningful resilience;
or 4,000–5,000 litres to maintain a carefully prioritised garden through several rainless months.

The rain is available.

The roof can collect it.

The real questions are whether we have the space, infrastructure and determination to store it—and whether we are prepared to redesign our gardens so that every stored litre goes further.

A water butt is an excellent beginning.

In a changing climate, it may no longer be the complete answer.