Why your drains block every spring

Late winter and early spring are common times for tree-root blockages in older drains.

Across Melbourne’s eastern suburbs, our residential plumbers often see the same pattern: a drain works normally through winter, then slows or backs up as the weather warms. Sometimes it is the same drain that was cleared the previous year.

Roots become more active as the soil warms and naturally grow towards moisture. If an older drain has a cracked pipe or failed joint, even a small leak can attract nearby roots.

By the time a blockage is obvious, the pipe defect may have been there for years. Clearing the roots gets the water moving again, but the underlying damage still needs to be identified.

What happens underground as the weather warms

Root growth increases as soil temperatures rise through late winter and early spring.

When a drain joint cracks or separates, small amounts of moisture can escape into the surrounding soil. Nearby roots grow towards that moisture.

Even a small opening can allow fine roots to enter. Once inside the pipe, they thicken and branch, catching paper, wipes, fat and other debris.

Over time, this build-up restricts the flow and can eventually cause a complete blockage.

Which drains are most at risk in Melbourne’s east

Many Melbourne homes built before the 1970s have earthenware or clay drains made from short pipe sections with mortar-sealed joints.

Over decades, the mortar can deteriorate and ground movement can shift the joints. Melbourne’s reactive clay soils expand and contract as moisture levels change, which can place extra movement around older pipework.

Older homes with mature gardens or established street trees are therefore more likely to experience root intrusion through damaged joints or cracks.

PVC drains became more common from the 1970s onwards. They use longer pipe lengths and sealed joints, so they are generally less vulnerable to roots. They can still develop problems if a joint is poorly made, a section settles, or the pipe is damaged.

Signs roots are already in your drain

Common warning signs include:

• Gurgling from a toilet or floor drain when another fixture, such as a sink or washing machine, empties
• Slow drainage at several sinks, showers or toilets at the same time
• A blockage that returns in the same place every 12 to 18 months
• A strip of lawn above the drain line that stays noticeably greener or denser than the surrounding grass
• Damp ground or a sewer smell in the yard
• Water backing up at the lowest fixture or drain point, often a shower or outdoor drain grate

One slow fixture can be a local blockage. If several fixtures drain slowly or gurgle at the same time, the main drain is more likely to be involved.

Why clearing the roots does not fix the pipe

Mechanical clearing or high-pressure jetting removes the root mass inside the pipe and restores the flow.

If the crack or failed joint remains, roots can grow back through the same opening. In some cases, the blockage returns within 12 to 18 months.

Clearing is often the right first step when a drain is backed up. The important next step is inspecting the pipe so the cause of the blockage is not missed.

A CCTV inspection can locate the defect and show the condition of the drain. If the pipe is suitable, it can then be relined from the inside to seal cracks and joints without excavation.

Whose pipe is it — yours or the water authority’s?

In general, the property owner is responsible for drains within the property boundary, up to the point where they connect to the water retailer’s sewer. Yarra Valley Water says blockages in private pipes, or in a combined drain shared by several properties, are the owner’s responsibility and should be handled by a licensed plumber (Yarra Valley Water — Responsibilities).

The water retailer depends on where you live. South East Water covers Knoxfield, Rowville, Ferntree Gully, Scoresby, Boronia, Wantirna and Wantirna South. Yarra Valley Water covers many northern and inner-eastern suburbs, including Kew, Hawthorn, Camberwell and Box Hill (Victorian Government — water corporations).

Once a blockage is beyond the property connection point, it is generally the water retailer’s responsibility. Most household drain blockages, however, are on the private side of the connection.

What to do before spring

• If your drain has blocked in the past two years, consider arranging a CCTV inspection before it happens again. Knowing whether the pipe is cracked, displaced or otherwise damaged will help determine the right repair.
• Before planting a large tree near a drain line, check where the pipe runs. Your water retailer can provide a property sewerage plan, and keeping large-rooting trees well away from ageing drains can reduce the chance of future problems.

Need help with a recurring blocked drain?

A drain that has blocked before may block again if the underlying cause has not been repaired. Finding the defect early can help prevent repeat call-outs and more extensive damage.

Triple Eight Plumbing handles blocked drains, CCTV inspections, pipe relining, hot water, burst pipes and general maintenance across Melbourne’s eastern suburbs. Submit a quote request or call us on 1300 29 27 31.