How to Winterize a Rain Barrel Before an Austin Freeze

Short answer: Before a hard freeze, empty the barrel, leave the spigot open, take off the hose, and put the downspout back so roof water lands at least 5 feet from the house. Then open the first-flush chamber’s cleanout and pull or cap the diverter. Camp Mabry averages 11.9 days a year with a low at or below 32°F. That’s few, but real, and a drained 55-gallon barrel under 500 square feet of roof refills with about a quarter inch of rain. Big cisterns are different: don’t drain the tank. Protect the exposed valves, pipes and pump, and follow the tank maker’s manual.

What to do

Part	Why it freezes	Before a hard freeze
Barrel (full plastic)	Water expands about 9% as it freezes, enough to crack a full plastic barrel (Penn State Extension)	Drain it. Store it indoors or upside down, tied down
Spigot or shut-off valve	Small body that stays full of water	Leave it open after draining, or remove it
Garden hose	Holds water along its length	Disconnect, drain, store
Downspout diverter	Sends water to the barrel and holds some in its fittings	Remove it and cap the hole, or reconnect the cut downspout section
Overflow hose	Water sits in low spots	Drain it, and make sure it runs away from the slab
First-flush chamber	It’s built to hold the first flush of each rain	Open the cleanout cap and let it empty
Large cistern	Exposed valves, pipe runs and pumps	Don’t drain the tank by default. Follow the manual. Protect the exposed parts

How often Austin freezes, and what that means for your barrel

The National Weather Service’s normals table for Camp Mabry lists, on average, 11.9 days a year with a low at or below 32°F: about 0.8 in November, 3.4 in December, 4.7 in January, 2.3 in February and 0.7 in March. Those are days with a freezing low, not separate freeze events, and they don’t tell you when the first freeze comes. NWS keeps a separate record for the Bergstrom airport station, and the two don’t have to match. Your yard may run colder or warmer.

A day with a freezing low isn’t the same as a barrel-cracking freeze. The real risk is a hard freeze. Penn State Extension defines that as below 28°F for an extended period, and says that’s enough to turn a barrel of water into ice. Austin has had that. The NWS described February 10 to 18, 2021 as an “unprecedented and historical eight-day period of winter weather” across South-Central Texas, with temperatures in the single digits and teens and burst water pipes across the region.

So you have two reasonable plans:

Season shutdown (what the extension guides recommend). Drain and disconnect before the first hard freeze, and hook it back up after the last one. This is the safe choice if you travel in winter or don’t watch forecasts.
Freeze-watch (our reasoning, not an extension recommendation). Keep collecting through the mild stretches, and run the full drain-down below whenever the forecast calls for a hard freeze. It only works if someone is home to do it the day before.

The math: draining costs you almost nothing

People hesitate to drain a full barrel because it feels like throwing water away. Here’s the trade:

Refill time. One inch of rain on one square foot is about 0.62 gallons. Say 500 square feet of roof feeds the barrel and you assume 80% of the water makes it in: 500 × 0.62 × 0.8 = about 249 gallons per inch. A drained 55-gallon barrel is full again after about 0.22 inch of rain.
Winter rain. Camp Mabry’s normal is 2.72 inches in December and 2.64 in January. That’s roughly a dozen refills’ worth in a normal month (2.72 ÷ 0.22). It’s a normal, not a forecast.
What you’re protecting against. 55 gallons that freezes solid needs about 9% more room, roughly 5 extra gallons of volume, inside a barrel that has no room to give.

Draining loses you one barrel of water. A cracked barrel, valve or diverter costs a replacement.

Step by step: drain, divert, disconnect

Pick where the water goes first. 55 gallons is about 7.4 cubic feet of water. Don’t open the spigot next to the slab. Run a hose from the spigot to a bed or lawn that slopes away from the house. Pacific Northwest National Laboratory (PNNL) building guidance says to carry roof water at least 5 feet from the building onto ground that slopes away.
Drain the barrel. Open the spigot and let it empty. Tip it to get the last few gallons out.
Leave the spigot open, or take it off. Rutgers Cooperative Extension says to leave the faucet open. The Chicago water district’s barrel instructions say to remove the shut-off valve before winter. Either way, nothing should be trapped behind a closed valve.
Disconnect the hose. Drain it and store it. Austin Water’s cold-weather advice is the same for any outdoor faucet: hoses off before freezing weather.
Deal with the diverter or the cut downspout. If you have an in-downspout diverter, one state environmental agency’s kit instructions say to pull the diverter out and screw the winter cover over the hole. If your downspout was cut to feed the barrel, put the saved section back. Rutgers suggests a short piece of downspout and a connector, strapped to the wall.
Add an elbow and an extension. With the barrel off, the downspout needs somewhere to send water again. Point the elbow away from the house and use an extension so the outlet lands at least 5 feet out. Our downspouts and drainage page covers extensions and buried lines.
Empty the first-flush chamber. The Texas Water Development Board’s manual describes the common standpipe type: it fills first in every rain, drains slowly through a pinhole or a slightly open hose bibb, and has a cleanout at the bottom. That slow drain is easy to clog with roof grit. Before a hard freeze, unscrew the cleanout cap and let it run dry. A 4-foot section of 4-inch standpipe holds about 2.7 gallons (TWDB: about 18 inches of 4-inch pipe per gallon).
Drain the overflow hose. Lift it so the low spots empty. Make sure it still points away from windows and foundations, as the Chicago instructions put it.
Clean and store the barrel. Winter is a good time to scrub out sediment, replace torn screens and worn valves (Penn State). Store it in a garage or shed, or upside down outside so it doesn’t fill with rain. An empty barrel is light. Rutgers suggests tying it to a 2-by-2 stake so wind doesn’t move it.

Plastic barrel vs. metal tank

Full plastic barrel: this is the case the extension guides describe. Ice can crack it, especially when it’s full or nearly full, and leftover ice also blocks the barrel from taking new water (Penn State).

Metal tanks: we couldn’t find a manufacturer or extension source that compares freeze damage in plastic and metal tanks, so treat this as reasoning. The 9% expansion is the same in any container, and the weak points in any tank are the parts where water is trapped in a small space: spigots, bulkhead fittings, valves and exposed pipe. Lined steel tanks add the liner. Check the maker’s instructions for your model.

Large cisterns: protect the parts, don’t drain the tank

A 1,000- or 3,000-gallon tank is not a big rain barrel. Draining it before every freeze would dump thousands of gallons, and the water in it takes far longer to freeze. BARR Plastics, a tank seller, notes that the larger the tank, the longer the water takes to freeze.

We couldn’t find a published winter procedure from a major poly tank manufacturer, so start with your own tank’s manual and warranty. Look for any freeze exclusion. Then check the parts that freeze first:

Exposed spigots and valves: insulate them or put them in an insulated box (BARR).
Above-ground pipe runs: drain them or insulate them.
Pumps: a pump house or insulated box (BARR), and the pump maker’s own cold-weather instructions. Pressurized systems belong to a rainwater specialist or plumber.
First-flush chamber: empty it, same as step 7.
Overflow: keep it clear. TWDB says tank overflow should be routed so it doesn’t undermine the tank pad or affect the foundation of any structure, and that the pad should be checked after intense rain. A frozen or clogged overflow can send a winter storm somewhere you didn’t plan.

When we work on gutters that feed a tank, we check where the overflow goes, too. Our rainwater collection gutters page explains how we route roof area, first-flush and overflow.

When you hook it back up: CDC screening

Penn State says to reconnect after the last hard freeze has passed. When you do:

Screen where water comes in, or empty the barrel at least every 10 days. That’s the CDC’s advice for stopping mosquitoes from laying eggs. A gutter guard is not an insect screen. The barrel inlet needs its own.
Use a first-flush diverter to send the dirtiest water away from the barrel (CDC).
Keep rainwater out of drinking-water pipes. The CDC says to make sure rainwater can’t enter pipes carrying safe tap water. Texas law adds rules if a system uses public water as a backup: cross-connection safeguards, and a backflow assembly or air gap on systems over 500 gallons (Health and Safety Code §341.042).
Use it on plants you don’t eat. The CDC suggests tap or bottled water for drinking, cooking, brushing teeth, rinsing produce and watering edible plants. Roof water can carry germs and chemicals, and first flush and screening don’t make it drinkable.

Spring is also when the live oaks drop tassels and pollen into everything. Clean the gutters feeding the barrel after that drop. See gutter cleaning.

FAQ

Do I need to drain my rain barrel in winter in Austin?

Before a hard freeze, yes. Camp Mabry averages 11.9 days a year with a low at or below 32°F, and a hard freeze (below 28°F for hours) can freeze a barrel solid. You can shut it down for the season, or keep it running and drain it whenever a hard freeze is forecast.

Can I leave my rain barrel outside in winter?

Yes, once it’s empty. Store it upside down so it doesn’t fill with rain, cover or screen the inlet, and tie it down so wind can’t move it. Leave the spigot open or remove it.

Will a rain barrel freeze in Texas?

It can. During the February 2021 storm, NWS reported temperatures in the single digits and teens across South-Central Texas over an eight-day stretch. A full barrel in weather like that is at risk, and you won’t always get much warning.

Should I drain a big cistern before a freeze?

Usually not the tank itself. Protect the exposed spigots, valves, pipe runs and pump, empty the first-flush chamber, and follow the tank manufacturer’s manual and warranty. If the tank has a pump or a backup water connection, ask the installer.

Is rainwater harvesting even legal in Texas?

Yes. Texas law encourages it, and HOAs can’t ban rain barrels outright. We cover the details and where the myth comes from in Rainwater Harvesting Isn’t Illegal in Texas. For other winter prep, see our fall exterior checklist, the FAQ, and our upcoming post on Austin’s first freeze.

Sources

Request a gutter estimate. We’d measure the roof area feeding each barrel or tank and check where every downspout, extension and overflow sends its water.

Winterize Your Rain Barrel Before a Texas Freeze