Rain Barrel Rules Changed, and the Fall Shutdown Is the Part Buyers Miss

Rain barrels used to be a legal question in parts of the United States, because in prior-appropriation states the rain landing on a roof is already allocated downstream. That argument has mostly been settled with numbers rather than prohibitions. Colorado’s HB16-1005, signed May 12, 2016 and effective August 10, 2016, permits collection at a single-family home or a multi-family residence with 4 or fewer units provided that a maximum of 2 rain barrels with a combined storage capacity of 110 gallons or less are used, the water is used on the property where it was collected, and it goes to outdoor purposes such as lawn irrigation and gardening.

That is the shift worth understanding in October: the question is no longer whether you may put a barrel under a downspout, but how big a barrel the rule and your roof justify, and what you do with it before the first freeze. We have tested nothing. The figures below come from a state legislature, EPA, a university extension fact sheet and NOAA.

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A practice that used to be restricted now sits inside written state limits

Colorado’s HB16-1005 took effect on August 10, 2016 and permits a maximum of 2 rain barrels with a combined storage capacity of 110 gallons or less at eligible homes, with the water used outdoors on the property where it fell. EPA publishes consumer guidance on barrels and includes rainwater harvesting as a control in its National Stormwater Calculator.

Our editorial reading of the cited data, not a forecast. How it is scored

By the numbers

• 623 galRunoff a one-inch rain event can produce on a 1,000-square-foot roofUT Extension
• 110 gallonsCombined capacity Colorado allows across two residential rain barrelsColorado General Assembly
• 460 lbApproximate weight of a filled 55-gallon rain barrelUT Extension
• 1991–2020Period covered by the current NOAA US Climate Normals for local rainfall lookupsNOAA NCEI

From a legal argument to a written limit

Colorado is the clearest case because the limits are numeric and short. The enacted summary for HB16-1005 covers single-family homes and multi-family residences with 4 or fewer units, caps collection at 2 rain barrels with a combined storage capacity of 110 gallons or less, requires that the collected precipitation is used on the residential property on which the precipitation is collected, and restricts it to outdoor purposes such as lawn irrigation and gardening.

Federal agencies now treat barrels as ordinary stormwater equipment. EPA’s consumer page says rain barrels capture water from a roof and hold it for later use such as on lawns, gardens or indoor plants, and that collecting roof runoff reduces the amount of water that flows from your property. EPA’s National Stormwater Calculator, which runs the agency’s own Storm Water Management Model, lists rainwater harvesting with rain barrels or cisterns as a green infrastructure control; that page was last updated May 18, 2026. Rules vary by state and utility, so read your own state guidance before buying.

The modern rule is a capacity number and a use restriction, not a ban.

The arithmetic a 55-gallon barrel runs into

University of Tennessee Extension publishes the figure that reframes the purchase: a one-inch rain event can generate up to 623 gallons of water on a 1,000 square foot roof, enough to fill over ten 55 gallon rain barrels. A single barrel is not storage for a storm, it is a bucket that fills early and overflows. The same sheet works the small case: one quarter of a 1,000-square-foot roof generates about 70 gallons each time it rains half an inch, which already exceeds one barrel. Extension guidance is to direct all excess water into lawn or bed area, away from the house foundation.

The second number that changes the shopping list is weight. A full 55-gallon barrel weighs about 460 pounds, so the stand has to be level and secure to prevent tipping, on a raised base of concrete blocks or composite lumber rather than untreated wood, which may rot. Height is not cosmetic: these systems run on gravity, so the spigot height decides whether a watering can fits under it or a soaker hose will run. For scale, the same sheet notes that 30 to 40 percent of a home’s summer water bill can go to outdoor use, and that 55 gallons spreads one inch of water over roughly 88 square feet once. Read it alongside our brief on whether drip irrigation is worth it, because the same sheet suggests a soaker hose for gradual release.

Why the search is really about parts

Six of the ten Amazon completions name a component rather than the barrel, and that matches how these systems fail. A barrel alone does nothing: the diverter decides how much downspout flow enters it, the overflow fitting decides where the excess goes, and the spigot decides whether you can use the water without a pump.

A downspout diverter is the part that makes winter manageable, because most designs switch back to the downspout without dismantling anything. That matters in October, when you want the gutter feeding the drain again rather than a barrel you have stopped emptying.

• Diverter: how it attaches to a 2-by-3, 3-by-4 or round downspout, and whether it can be switched off
• Overflow: an outlet near the top with somewhere to send water away from the foundation
• Screen: a strainer at the inlet, which also keeps the barrel closed to insects
• Spigot: height above the base, and whether a hose thread fits it
• Base: level, able to carry about 460 pounds, and not bare untreated timber

Buy the diverter and the base with the barrel, or the barrel sits unused.

The October job: drain it, open it, aim the overflow

The shutdown step is almost never on a product listing. University of Tennessee Extension’s winter instruction is that barrels can be left outdoors, however, unless collecting water to use during the winter months, attach water hose to open spigot and drain water onto lawn or in bed area. Leaving the spigot open with a hose attached is the whole method: water cannot sit and expand in the barrel, and anything that arrives runs out.

Two related habits come from the same sheet: inspect the inside of the barrel in both fall and spring and clean it as required, and disconnect the barrel entirely when cleaning siding or a roof with soap or chemicals, because that runoff ends up in the barrel. If you are shutting down outdoor water this month anyway, the barrel belongs on the same list as the hose bib — our piece on outdoor faucet covers and freeze protection covers the tap end of the job.

Who should buy now, and who should wait

Buy now if fall and winter rain is the wet part of your year and you have an outdoor use for the water, if your utility charges a stormwater fee a barrel reduces, or if a collapsible barrel suits a space a rigid one cannot reach. Buying in October also means installing in mild weather with the plumbing proven before spring.

Wait if you cannot answer the overflow question. A barrel with nowhere to send excess water beside a foundation is a drainage problem rather than a water saving, and the 623-gallon figure says it will overflow in the first real storm. Wait too if you have not read your own state rules, since the Colorado numbers are specific to Colorado. Check your local precipitation and freezing-day normals at NOAA first: the 1991–2020 US Climate Normals dataset carries more than 500 separate types of weather and climate statistic, including days with temperatures below freezing.

What to watch next

• Whether more states follow Colorado in writing numeric caps rather than leaving collection ambiguous
• Whether EPA replaces its rain barrel page, which carries a notice that it is no longer being updated
• Whether utility stormwater credits for barrels spread, since that changes the payback more than the barrel price

Where to start

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More: Garden and Backyard trends and how the Trend Signal is scored.

Questions readers ask

Are rain barrels legal?

In Colorado, HB16-1005 permits a maximum of 2 rain barrels with a combined storage capacity of 110 gallons or less at a single-family home or a multi-family residence with 4 or fewer units, with the water used outdoors on the property where it was collected. The bill was signed May 12, 2016 and took effect August 10, 2016. Other states set their own conditions.

How much water does a rain barrel actually collect?

University of Tennessee Extension states that a one-inch rain event can generate up to 623 gallons of water on a 1,000 square foot roof, more than ten 55-gallon barrels. A single barrel fills early and then overflows, so the overflow route matters more than the barrel size.

What do you do with a rain barrel in winter?

Unless you are collecting water through the winter, University of Tennessee Extension says to attach a water hose to an open spigot and drain the water onto lawn or into a bed area. Barrels can otherwise stay outdoors. The same sheet advises inspecting and cleaning the inside in both fall and spring.

Can you water vegetables with rain barrel water?

EPA notes that as rain water flows over a roof surface it can pick up pollutants such as bacteria from birds, and advises considering this before using barrel water on edible plants. University of Tennessee Extension says barrel water is not for human consumption and that vegetables should be washed well.