If your drain only overflows when it rains hard, the problem is usually in the stormwater system rather than the sewer. Rain sends far more water through the pipes than normal household use, so a line that is partly blocked copes all week and then fails in a downpour.
Sydney storms are short and heavy, which makes this very common. The pipe does not have to be fully blocked. It only has to be too small, too flat or too full of silt to carry the volume arriving in a few minutes.
Stormwater carries rain from your roof, driveway and yard. Sewer carries waste from your toilets, sinks and laundry. They are separate pipes with separate jobs.
Knowing which one is overflowing tells you a lot. Clear water with leaves and grit in it is stormwater. Grey or dirty water with an odour is sewer. Our guide on the difference between a stormwater and a sewer blockage goes through this in more detail.
Gutters, downpipes and surface pits feed a steady supply of leaves, dirt and roof grit into the stormwater line. Over the years this settles in the flatter sections and the pipe quietly loses half its capacity.
Stormwater pipes are often shallow, joined and sitting in damp soil, which is exactly what tree roots look for. A root mass acts like a strainer and catches everything that washes past it.
Ground movement, old clay pipe and heavy vehicles over a driveway all cause pipes to crack or sag. Water then slows at that point and soil washes into the line. The signs of a cracked or broken drainage pipe are worth knowing if this keeps happening.
Sometimes the pipe is fine and the entry point is the problem. A grate covered in leaves or a pit filled with mulch stops water getting in at all, so it runs across the yard instead.
Rainwater running across the lawn is a nuisance. Water pooling against the house, running under a slab or coming back up inside is a different matter. So is any sign of sewage, which means the two systems are interacting or the sewer line is blocked as well. That situation is covered in why drains back up and overflow, and it should be looked at straight away.
Guessing at a buried pipe wastes money. A camera run through the line shows silt, roots, cracks and sagging sections, and it marks the depth and position so any repair is targeted. From there the pipe can be jetted clean, or relined where the damage is structural.
We handle blocked drains and pipes across Sydney, and where a line is broken rather than dirty, pipe relining repairs it without digging up the yard or driveway.
Rain puts far more water through the system than normal daily use. A pipe that is half blocked copes fine with a shower or a washing machine, but it cannot handle a downpour, so the water backs up and finds the lowest opening.
Pipes on your property are generally your responsibility, while the street drainage belongs to the council. If the overflow happens inside your boundary, start with your own stormwater line.
Yes. Water that cannot get away pools against footings, soaks into walls and erodes soil around the slab. Repeat flooding is worth fixing properly rather than waiting for the next storm.
Drains that overflow in rain rarely fix themselves, and every storm moves a little more silt into the line. Sydney Drain Surgeons can inspect the pipe, clear it and tell you honestly whether it needs repair or just a clean. Contact our Sydney drain team to get it looked at.
