How to Clear Blocked Stormwater Drains in Winter: A Practical Aussie Guide

It usually happens after a big downpour. The water that should be running away from your house is sitting there instead, pooling near the downpipe or spreading across the yard. You poke your head outside, check the gutter, and realise the stormwater drain is not doing its job.

Winter is exactly when this shows up, because winter is when the drains earn their keep. Heavy rain, wind-blown leaves and the general mess a storm leaves behind all find their way into the system. The good news is that a lot of blockages are preventable, and a fair few are clearable by a careful homeowner. This guide explains what you can safely do yourself and when to stop and call a professional.

Why stormwater drains block in winter

Stormwater drains carry rainwater away from your roof, driveway and yard. They are built to handle water, not the other stuff that comes with it, and winter supplies plenty of that.

Leaves and twigs wash off the roof and into the gutters and downpipes. Mud and silt build up when heavy rain runs across bare ground. Roof debris finds its way into the system during storms. Tree roots work their way into underground pipes, and rubbish pushed along by runoff can jam a grate. Over time these materials narrow the pipe until the water backs up.

Understanding the cause matters, because it tells you what to look for. A blockage caused by leaves is usually near the top of the system and easy to reach. A blockage from tree roots is underground and is a job for a professional with the right gear.

The signs to watch for

Catching a blockage early is far cheaper than dealing with a full overflow. These are the signs that your stormwater system is struggling.

Water draining slowly from an outdoor grate is usually the first clue. Pooling water near a driveway, path or garden bed after the rain has stopped points the same way. Gurgling sounds from a pipe after rain mean air is trapped by a blockage. Overflowing grates during a shower, or water backing up near your foundations, are the signs to take seriously, because that is when water starts looking for a way into the house.

If you notice any of these during winter, act sooner rather than later. A small blockage you can clear yourself becomes a bigger problem the longer it sits.

Clearing the easy blockages yourself

For blockages near the surface, a careful homeowner can often sort the problem without calling anyone. Work through these steps in order, and stop if something does not feel right.

Start with the grates. Lift any grate you can access and remove the leaves, sticks and rubbish sitting on top of it by hand or with a garden tool. Wear gloves, because you do not know what is in there. This single step clears a surprising number of blockages, because most start with debris sitting over the opening.

Next, flush the drain with a garden hose. Once the surface is clear, run water down the drain to shift anything loose further along. A standard hose will not clear a solid blockage, but it will move the soft material that a heavy rain has pushed partway down.

Then check the downpipes. A downpipe that has come loose, or that is clogged where it meets the underground drain, is a common cause of stormwater problems. Make sure each downpipe is clear and properly connected. If leaves have built up in the pipe, you may be able to clear the top of it, but be careful not to push the blockage further down.

For shallow pipes you can sometimes use drain rods to break up a minor obstruction. Only do this if you are confident the pipe is shallow and in good condition. Forcing rods down an old or fragile pipe can do more harm than good, so if there is any resistance, stop.

When to call a professional

There is a clear line between what a homeowner should attempt and what needs a professional, and it is worth knowing where that line is. DIY methods work for surface blockages and soft material. They do not work for blockages that are deep, solid or caused by damage.

Call a professional if water keeps backing up after you have cleared the surface and flushed the line. Call if a blockage keeps returning in the same place, because that pattern usually means something structural, like a root or a collapsed pipe. Call if you suspect tree roots, which you cannot clear with a hose. And call if there is any chance an underground pipe is damaged or collapsed, because digging into that yourself is not a good idea.

A licensed plumber or drain specialist has tools a homeowner does not. A CCTV camera goes down the pipe and shows exactly where the blockage is and what is causing it. High-pressure water jetting clears blockages that rods and hoses cannot shift. When you call, you are paying for diagnosis as much as for the clear, and that diagnosis is what stops the problem from coming back every few weeks.

Stopping the blockages before they start

Prevention is cheaper than any repair, and most stormwater blockages are preventable with a bit of seasonal maintenance.

Clean your roof gutters before winter properly arrives. A gutter full of leaves is a downpipe blockage waiting to happen, so clear the gutters when the trees have dropped their leaves and again if a big storm hits. Consider leaf guards on the gutters and drains that collect the most debris, because they stop the leaves getting in at all. Trim any tree branches that overhang your roof or drainage lines, and think twice about planting trees close to underground pipes. Have the drains inspected every year or two if your property has older pipes or big trees nearby. And when you are gardening, do not wash soil and clippings into the outdoor drains, because silt is one of the quietest ways a drain fills up.

None of this is glamorous, but it is the difference between a winter where the water runs away and a winter where you are out in the rain with a hose and a pair of gloves.

Keep the water moving

A stormwater system does its job best when you barely notice it. The water runs off the roof, down the pipes and away from the house, and you get on with your day.

The way to keep it that way is to clear the easy blockages early, know when a problem is beyond a hose and a pair of rods, and do the seasonal maintenance that stops most blockages from forming in the first place. If a blockage keeps coming back, or water is finding its way towards your foundations, that is the moment to call a licensed plumber and let them put a camera down the pipe. A small investment in the drain now beats a flooded yard, or worse, a flooded house, later.