How to Unclog a Balcony Drain
To unclog a balcony drain, first lift the strainer cover, remove the leaves, soil and sand with a gloved hand, and scoop the sludge out of the drain opening with a plastic spoon. Then test the flow with a bucket of water. If water still collects, use a plunger or a thin drain snake. If water overflows on several floors' balconies at once, the problem is in the shared downpipe.
The question of how to unclog a balcony drain usually comes up during the first downpour, when water pooling on the balcony starts creeping over the threshold towards the living room. Unlike a kitchen or bathroom drain, a balcony drain is open to the weather: leaves blown in by the wind, soil washing out of plant pots, sand and bird feathers all collect right on top of the strainer. Once wet, this debris sticks together and turns to sludge, and it can block a narrow drain opening in a single rainy night.
The good news is that most balcony blockages form in the first few centimetres of the drain. Lifting the strainer cover, taking out the build-up by hand and flushing the line with water is often enough. In apartment buildings, though, the balcony drain connects through a downpipe to the floors below and on to the building's rainwater or sewer line. That means neglect on one floor can leave the neighbour's balcony below under water too. We explain the steps and their limits in order.
Why does a balcony drain get blocked?
What blocks a balcony drain usually comes from outside. Different debris stands out depending on the season and how the balcony is used.
Dry leaves and pine needles
On balconies close to trees, leaves pile up in layers on top of the strainer in autumn. When rain soaks them they mat together and form a cover that stops water from passing through the strainer.
Pot soil and watering residue
When you water plants, the muddy water running out from under the pots carries fine soil to the drain. The soil settles in the pipe bend, hardens as it dries and gets a little thicker with every watering.
Sand, dust and building debris
Fine sand carried by the wind, dust from nearby construction and pieces of plaster left over from balcony renovations fill the strainer. Once sand mixes with water it becomes heavy and settles in a layer at the bottom of the pipe.
Feathers, nesting material and droppings
On balconies where pigeons often perch, feathers, bits of rubbish and droppings collect around the strainer. This mixture causes blockages as well as bad smells and pest problems.
A narrowing in the shared downpipe
The water from the balconies above flows into the same vertical pipe. If there is a blockage in the lower part of the pipe or at the connection in the basement, the water cannot drain down and overflows from the lowest balconies.
Is your balcony drain blocked? Look for these signs
You usually notice a blocked balcony drain when the rain starts. Small signs show up in dry weather too.
Standing water after the rain
If water is still standing on the balcony floor hours after the rain has stopped, the drain is either partly blocked or the floor does not slope enough towards the strainer.
A ring of mud around the strainer
The brown residue that drying water leaves around the strainer shows that soil and sand are flowing towards the drain, and that some of it is staying behind inside.
Smell and flies from the drain
Leaves and bird debris rotting inside the pipe give off a heavy smell. Because water stays standing, mosquitoes and small flies multiply around the drain in summer.
A complaint from the floor below
Dampness on the ceiling of the neighbour's balcony below, or water marks on the facade, can mean the downpipe is blocked somewhere and water is seeping out at the joints.
My balcony drain is blocked: how can I clear it?
If your balcony drain is blocked, start by cleaning the strainer. In most cases the job ends there. Do every step standing or kneeling on the balcony floor, and do not carry out any task that means leaning over the railing or climbing on something.
Lift the strainer cover and remove the debris by hand
If you can see leaves, soil or feathers on top of the strainer and the water is draining slowly, this is the first thing to do.
- Put on thick garden gloves and bring a rubbish bag with you.
- Pick up the leaves and soil around the strainer by hand before sweeping, and do not push them towards the drain.
- Lift off the strainer cover by pulling it up or by undoing its screws.
- Scoop the sludge out of the drain opening with a plastic spoon or an old spatula and put it in the bag.
- Rinse the cover with a brush and put it back, then pour a bucket of water in slowly to check the flow.
Because you are in contact with bird droppings, do not work without gloves, and wash your hands with soap when you finish. If the strainer cover is rusted and stuck, forcing it off can damage the tiles and waterproofing around it.
Pull the sludge out with a wet and dry vacuum cleaner
If the drain opening is packed with wet soil and sand and you cannot reach it by hand, a wet and dry vacuum can draw this sludge out of the pipe.
- First remove as much standing water from the balcony as you can with a bucket and a cloth.
- Set the vacuum to wet mode and place the end of the hose directly on the drain opening.
- Wrap a wet cloth around the edges of the opening so the suction is directed into the pipe.
- Apply short bursts of suction a few times, then test the flow with water.
Never put an ordinary household vacuum cleaner into water or mud: the motor will be damaged and there is a risk of electric shock. Make sure the socket and cable are well away from the wet floor.
Flush the line with a garden hose
If the drain opening is clear but water slows down further along the pipe, you can wash out the thin layer of soil and sand in the pipe with a hose.
- Push the end of the hose about a hand's length into the drain opening.
- Block the area around the opening tightly with a wet cloth, so the water cannot come back and is pushed into the pipe under pressure.
- Open the tap slowly and watch whether water is collecting on the balcony.
- If the water is draining freely, let it run for a few minutes, then turn the tap off.
If the water starts rising on the balcony, turn the tap off straight away: pushing water into a blocked line can cause an overflow on the balcony below. It is a good idea to tell the neighbour below before you start.
Use a plunger to shift the blockage
If the strainer is clean and the water you run in with the hose comes back, the blockage may be in the first bend of the pipe, and a plunger can shift it.
- Remove the strainer cover and seat the rubber cup of the plunger fully over the drain opening.
- Leave a few fingers of water, enough to cover the rubber cup.
- Holding the plunger upright, push and pull fifteen to twenty times, lifting it away sharply on the last pull.
- If the water drains away, flush the line with a bucket of water. If not, repeat the process for a few rounds.
Do not use a plunger if you have poured a chemical drain opener into the drain, as splashing product can cause burns. On square or very wide strainers the rubber cup may not seat properly, and then no pressure builds up.
Clear the sludge in the bend with a drain snake
If the plunger did not work and you think the blockage is close to the drain opening, a thin hand snake can reach the first bend.
- Remove the strainer cover and spread an old cloth beneath the drain opening.
- Feed the flexible snake in slowly, and when you reach the bend, advance it by turning the handle.
- At the point where you feel resistance, turn the snake to loosen the sludge.
- Pull the snake back, scrape the debris on its tip into the bag, then flush the line with plenty of water.
Do not force the snake: the joints of old downpipes running down the outside of the building can easily come apart. If the snake will not go further after a few metres, the blockage is in the downpipe and cannot be cleared with hand tools.
What not to do with a balcony drain
Leaning over the railing or climbing on something
Leaning over the railing, or climbing on a chair or ladder to reach the downpipe from outside, carries a risk of falling. Any job you cannot reach from the balcony floor should be left to a crew.
Sweeping soil and sand into the drain
Pushing dirt towards the drain with a hose while washing the balcony makes the soil collect in the pipe bend. Sweep the dirt up and put it in the bin first, then wash the floor.
Pouring in a chemical opener
Drain openers do not dissolve soil, sand or leaves. Sitting in the pipe, they can damage the PVC and may end up in the rainwater line. If you have poured some in, tell the technician who comes, and do not mix it with any other product.
Using boiling water or a wire coat hanger
Boiling water softens the joints of a PVC downpipe. An unbent coat hanger scratches the inside of the pipe and can get caught in the bend.
Sealing the drain permanently with silicone
Closing the drain off completely because of smell or insects lets water come over the threshold in the first downpour. Fitting a strainer with an odour trap is the right fix for smell.
When should you call a crew?
If water keeps collecting on the balcony even though you have cleaned the strainer and tried the plunger and snake, the blockage is deep in the downpipe or at the point where it joins the building's main line. If water overflows on several balconies on the same facade at once, or you are told that water is coming up on the lower-floor balconies or in the basement, the problem is in the shared line and building management needs to know as well. In some older buildings the balcony drain is connected to the shared sewer stack. If a heavy sewer smell comes from the drain, this connection should be checked too.
If you would need to reach the part of the downpipe that runs down the facade from outside, do not try to do the job yourself. When rainwater is coming over the threshold into the living room or a bedroom, waiting also makes the damage to the parquet and walls worse. In these cases, a crew that can see inside the pipe and clear the line with machines is the safer solution.
How do we clear a balcony drain blockage without breaking anything?
The Cantley team first checks the balcony and the other floors that share the same line. A camera sent in through the drain opening or the building's manhole shows the inside of the downpipe on a screen, and we work out at which floor level or which connection the blockage is. We explain what will be done to you, and to building management if needed, before we start work.
For packed soil and leaves, a motorised drain snake or a robotic machine moves through the pipe and breaks up the blockage. The layer of sand and mud and the build-up in the main line are washed out with high-pressure water jetting. Because the whole job is done through the drain opening and the manhole, the balcony floor and the facade are not broken. When the job is finished, a final camera check is made and you can see together that water flows freely from top to bottom.
Keeping your balcony drain clean
- In October and November, before the winter rains begin, lift the strainer cover, clean inside the drain and test the flow with a bucket of water.
- Put saucers under your plant pots so that the muddy water that runs out when you water goes into the saucer, not the drain.
- Before washing the balcony, sweep up the leaves, soil and sand and put them in the bin.
- On balconies close to trees, put a domed strainer or a fine wire mesh over the strainer to catch the leaves.
- On balconies where pigeons perch, clear the bird debris before it builds up.
- Make it a habit to check the top of the strainer in autumn and after heavy rain.
- Plan with building management to have the downpipes and the building's manhole checked once a year.
Frequently asked questions
How do you unclog a blocked balcony drain?
A blocked balcony drain is cleared by lifting the strainer cover and removing the leaves, soil and sand inside with a gloved hand. Scoop the sludge out of the drain opening with a plastic spoon and test the flow with a bucket of water. If the water still will not go, you can use a plunger, then a thin drain snake. If those do not work either, the blockage is in the downpipe and has to be cleared with a machine.
Where does a balcony drain connect to?
In most apartment buildings, the balcony drain connects to a vertical downpipe, and from there to the building's rainwater line or sewer line. Which one it is depends on the age and design of the building. Because the balconies above use the same pipe, a blockage on one floor usually causes overflow on the balconies below that floor.
Can you close off a balcony drain?
Closing a balcony drain off completely is not recommended: on open or semi-open balconies, rainwater needs somewhere to go. If you have a smell or insect problem, you can fit a strainer with an odour trap or a lid. Even on glazed balconies, it helps to leave the drain open for washing water and possible leaks. During renovation work, covering the drain temporarily with tape is fine.
Why does my balcony drain smell bad?
A smell from a balcony drain usually comes from leaves, soil and bird debris rotting inside the pipe. If the drain is connected to the shared sewer stack and has no odour trap, sewer air can also come up in dry weather. Cleaning the strainer and flushing the line with water is often enough. A heavy smell that does not go away means the connection needs to be checked.
Can you pour a chemical drain opener into a balcony drain?
Pouring a chemical opener into a balcony drain is not recommended. Balcony blockages are mostly made of soil, sand and leaves, and no drain opener dissolves that debris. The product can sit in the pipe and damage the PVC, and it can be carried outside by the rainwater. Cleaning by hand, a plunger and a drain snake are both safer and more effective.
Why does water from the balcony above overflow onto ours?
If water from the balcony above overflows onto yours, the shared downpipe is blocked at the level of your floor or lower down. When the water coming from above cannot go down, it rises through the nearest outlet, which is your strainer. This affects all the flats that use the same pipe, so you need to tell building management and have the pipe cleared with a machine.
What should be done for the balcony drain before winter?
Before the winter rains, lift the strainer cover, clean the leaves and soil out of the drain, then check the flow with a bucket of water. Put saucers under your plant pots and use a leaf-catching strainer on balconies close to trees. If you notice water draining slowly, having the line cleared before the rains start prevents water getting inside during a downpour.
Other guides
How to Clear a Blocked Toilet
What to do first if the water is rising, how shared lines work in a building, and when to call a professional.
Read the guideHow to Unclog a Toilet Bowl
How to use a plunger, whether toilet drain openers are safe, and what happens when an object falls into the toilet.
Read the guideHow to Unclog a Bathroom Sink
Trap cleaning, drain snakes, and baking soda with vinegar: which one works and when.
Read the guideHow to Unclog a Kitchen Drain
The sink is blocked and the water won't drain: steps for grease build-up and the dishwasher drain.
Read the guideHow to Unclog a Shower Drain
Hair build-up, smells and pooling water in the shower and floor drain.
Read the guideHow to Unclog a Blocked Pipe
Blockages in PVC and old pipes, the shared drain pipe, and pipe-clearing attachments.
Read the guideHow to Unclog a Drain
The first minutes after a drain blocks: which line it is, what clears it and when to call.
Read the guideIf water keeps collecting on your balcony
If cleaning the strainer and hand tools were not enough, call 0212 923 66 85 or message us on WhatsApp. The Cantley team works 24/7 across all 39 districts of Istanbul, inspects the downpipe with a camera and clears your balcony drain without breaking anything.