The Sky's Own Tap: A Balcony Rain Harvest That Won't Flood the Neighbours

November rain is free, which is exactly the sort of price I like. On a small balcony, though, free water can feel like a luxury designed for people with gardens, downpipes and a shed full of mystery. Not so. With a washing-up bowl, a food-safe bucket, a funnel and a bit of careful positioning, you can catch enough of the sky's own tap to keep a few pots and a winter salad trough going through the grey weeks. You will not be watering an allotment. You will, however, feel mildly smug every time it drizzles.

Start with the maths, then lower your expectations

The useful rule of thumb is simple: 1mm of rain falling on 1 sq m of collection area gives you roughly 1 litre of water. A balcony bowl with an open top of about 0.25 sq m, then, catches around a quarter of a litre for every millimetre of rain. If November delivers 80mm across the month, that is theoretically about 20 litres. In reality, wind, splashing, overshoot and the fact that you will not always have the lid off mean you should expect something closer to 10 to 15 litres.

That is still plenty for a few balcony pots, a herb trough and a couple of houseplants that have been exiled to the sill. It is not enough to justify a full-scale irrigation system. Think of it as a cheerful top-up, not a utility company. By mid-November 2026, a modest setup should be giving you enough for a weekly watering can or two, especially if you add a second container under a gutter drip.

The kit: a bowl, a bucket and a bit of gutter nerve

The hero of this setup is a washing-up bowl. Not glamorous, but food-safe, wide-mouthed and easy to empty. Pair it with a lidded bucket or a 5-litre water container that has never held chemicals. Old fermentation buckets, rinsed-out catering tubs and sturdy picnic containers all work. Avoid anything that once held antifreeze, weedkiller or anything with a hazard symbol. Your tomatoes will not thank you.

A funnel is the other essential. Rain collected in a wide bowl needs transferring to a taller container without decorating your balcony floor. A cheap plastic funnel from a DIY shop is fine. So is a cut-down plastic bottle, as long as the edges are sanded or taped. Add a fine mesh sieve or a piece of insect netting over the funnel mouth to keep out leaves, moss and the sort of organic soup that turns water questionable within days.

If you have a length of mini guttering, you can get cleverer. A short run of gutter cable-tied to the balcony rail, angled gently towards a funnel, will collect more rain than a bowl alone. Do not drill into the building, divert a shared downpipe or attach anything to a neighbour's wall without permission. If you rent or lease, check your agreement first. The best balcony rain harvest is the one that can be removed in five minutes when the landlord visits.

Where to put it without becoming the balcony nuisance

Position matters more than capacity. Put your collector where rain actually falls, not where it looks tidy. A corner against the rail often catches more than a sheltered wall. Keep it out of walkways, away from the fire escape and away from any door that needs to open fully. A full 5-litre container weighs 5kg, and a larger bucket can easily hit 15kg or more, so think about balcony loading. Spread the weight near supporting walls and do not crowd one corner with every pot you own.

Neighbours are the other factor. Water splashing over the edge and dripping onto the balcony below is the fastest way to turn a wholesome hobby into a complaint. Use a lidded container with a small inlet hole, or place the bowl inside a larger tray to catch overflow. Angle any gutter run so that overflow goes back onto your own balcony floor and drains away, not over the rail. If your balcony has a solid parapet, keep the collector low and stable so wind cannot tip it. A couple of heavy stones in the base of an empty bucket help before it fills.

The midge problem, and the December fix

Standing water is a midge nursery. A bowl left open for a fortnight in a mild November is basically a spa with no reception desk. The fix is not complicated: keep it covered, keep it moving and keep it short-term. Use a lid with a small inlet, or stretch fine mesh over the top and secure it with a bungee cord. Empty and refresh the bowl every few days if it is open. Do not let leaves or compost stew in it. If you have room, a small airstone or a solar-powered fountain bubbler will keep water moving, but on a tiny balcony a lid and a bit of discipline are cheaper.

By December, you have two sensible options. Either use the water steadily on pots and then store the container dry, or keep a sealed, mesh-covered bucket for the winter and check it weekly. Do not leave an open bowl of water sitting under a plant pot saucer for weeks. That is how you end up with wrigglers and a sudden interest in pond ecology you did not ask for. If the water starts to smell or look cloudy, tip it onto established outdoor plants or dilute it into compost, then scrub the container with hot soapy water and rinse well.

What to do with the water

Rainwater is genuinely useful on a balcony. It is soft, free of the chlorine that can make tap water less than ideal for some plants, and it feels pleasantly subversive to water a rosemary cutting with something you caught from the sky. Use it on pots of winter salads, herbs, ferns and anything that sulks in dry indoor air. Do not drink it, obviously, and do not use it on anything you are about to eat raw without washing it first in clean water. Keep a small covered jug near the door for quick top-ups and leave the main container sealed.

A rain harvest will not solve every watering problem, and it will not make a north-facing balcony into a Mediterranean terrace. What it will do is give you a small, satisfying loop: the sky does something British and damp, your bowl catches it, and your pots get a drink without you wrestling a watering can through the flat. In a small space, that is a proper bit of seasonal cheer. Free water, a tidier balcony and one less reason to curse the forecast. I call that a November win.