Winter is the toughest season for a water butt. Freezing temperatures can crack plastic, damage fittings, and ruin a perfectly good rainwater harvesting system if you haven’t prepared properly. The good news is that winterising your water butt takes less than an hour and can add years to its lifespan.
In this guide, we’ll cover every approach to winter care, from the simplest method of draining and storing, right through to keeping your system active all year round with proper insulation.
Why Freezing Damages Water Butts
Water has a unique property that makes it dangerous in freezing conditions: it expands by roughly 9 per cent when it turns to ice. This expansion exerts enormous pressure on whatever contains it. A plastic water butt that’s completely full of water will experience thousands of kilograms of outward force as the water freezes. Polyethylene is flexible enough to handle some expansion, but the sudden, extreme pressure of a hard freeze will eventually cause cracks, especially along seams and around fittings.
The most vulnerable points are the tap outlet, the inlet hole where the diverter connects, and the bottom seam of the butt. These are areas where the plastic is thinnest or where there are already small stress points from manufacturing. Ice forming in these areas can split the plastic in a single night of heavy frost.
Option One: Drain and Store (The Simplest Method)
If you don’t plan to use stored water over winter, draining and storing your water butt is the safest option. Here’s how to do it properly.
Start by disconnecting the diverter from your downpipe. Most snap-fit diverters have a release clip or latch that lets you separate the two halves. Clean out any debris from the diverter mesh while you have it open.
Open the tap fully and let all the water drain out. You’ll be surprised how much comes out — even when you think it’s empty, tilt the butt to get the last few litres from the bottom. If your butt has a removable lid, take it off and tip the butt onto its side to drain completely.
Once empty, scrub the inside with a stiff brush and a mild solution of warm water and a few drops of washing-up liquid. This prevents any organic matter from rotting inside the butt over winter. Rinse thoroughly and leave the lid off for a few hours to air dry.
Store the empty butt upside down in a shed, garage, or under a covered area. This prevents rain from collecting in it and stops leaves and debris from blowing in. If you don’t have indoor storage, turn it upside down outside and weigh it down with a brick or two. Make sure the tap is left open so any moisture that does get in can drain out.
Wrap the diverter and hose in a plastic bag and store them indoors if possible. Rubber seals and gaskets can perish faster when left exposed to freeze-thaw cycles.
Option Two: Partial Fill and Insulate
Many gardeners prefer to keep collecting through winter — winter rain is free water, after all. If you want to keep your system active, you need to insulate it properly.
The key principle is to leave enough empty space in the butt for ice to expand without stressing the walls. A water butt that’s only two-thirds full has plenty of headroom for expansion. The water will freeze from the top down, and the empty space above gives the ice room to expand upward rather than outward against the walls.
Insulating the butt significantly reduces the risk of freezing. The most cost-effective method is to wrap the butt in bubble wrap, with the bubble side facing the plastic. Use duct tape or garden twine to hold it in place. Two or three layers provide excellent insulation. You can buy purpose-made water butt insulation jackets, which look neater and fit more snugly, but bubble wrap works just as well.
Don’t forget to insulate the tap. A frozen tap is a common problem, and it’s much harder to thaw than the main body of the butt. Wrap the tap housing separately with a thick layer of bubble wrap or an old sock. Some gardeners use pipe insulation foam, which you can buy from any hardware store for a few pounds.
The exposed pipe work between the diverter and the butt inlet should also be insulated. A short length of pipe insulation foam slipped over the hose will prevent it from freezing and cracking.
Option Three: Keep It Running
In milder parts of the UK, or during a relatively warm winter, you might not need to do much at all. If temperatures rarely drop below freezing for more than a few hours at a time, your water butt will probably survive without any special treatment.
That said, it’s worth taking a few precautions even in mild winters. Keep the water level below three-quarters full by using the water regularly. A butt that’s being emptied and refilled is much less likely to freeze solid than one that’s been sitting untouched for weeks.
Leave the tap slightly open — just a crack. This allows any water that freezes in the tap housing to expand without splitting the brass or plastic. It also lets a slow drip escape, which keeps water moving and reduces the chance of freezing.
Check on your butt after a hard frost. If you notice the water surface has frozen, don’t try to break the ice by hitting it — you risk cracking the butt. Instead, pour a kettle of warm (not boiling) water onto the ice surface to melt it gently. Better yet, float a small plastic bottle or ball in the water before winter. If the surface freezes, the floating object absorbs the expansion pressure and you can remove it to create a hole.
What to Avoid
There are a few common mistakes that cause more harm than good. Never add antifreeze or any chemical to your water butt. Even small amounts of antifreeze are toxic to plants, pets, and wildlife. Your water butt is for collecting rainwater for your garden — keep it chemical-free.
Don’t use boiling water to thaw a frozen butt. The sudden temperature change can cause thermal shock and crack the plastic. Always use warm water and apply it gradually.
Don’t overtighten fittings in cold weather. Plastic becomes more brittle at low temperatures, and over-tightening a tap or connector can create micro-cracks that will leak later.
Don’t ignore the diverter. A frozen diverter can crack just as easily as the butt itself, and if the ice blocks the downpipe, rainwater will overflow from the top of the downpipe rather than entering the butt. This can cause water to run down the outside of the pipe and soak your foundations.
Signs of Frost Damage
Even with the best preparation, frost damage can happen. Check your water butt carefully after a cold snap. Look for hairline cracks around the tap housing, the inlet, and along the bottom seam. These can be very fine and hard to spot when the butt is full, so empty it and inspect closely.
Small cracks can often be repaired with a waterproof sealant or a plastic weld repair kit designed for polyethylene. Larger cracks or splits usually mean the butt needs replacing. If you notice a crack, clean the area thoroughly, dry it completely, and apply the repair before refilling.
Final Checklist
Before winter sets in, run through this quick checklist:
- Drain and store, or insulate if keeping active
- Clean the interior if storing empty
- Insulate the tap and exposed pipe work
- Keep the water level below three-quarters
- Leave the tap slightly open
- Check for cracks after frost
Taking an hour to winterise your water butt now will save you the cost and frustration of replacing it come spring. A well-cared-for water butt will last fifteen years or more — and that’s a lot of free water for your garden.