Why Tree Roots and Old Pipes Keep Blocking the Same Drain

Two jobs before you call anyone about a drain that keeps blocking: work out whether the problem is one fixture or the whole line, and write down when it last happened. It takes about fifteen minutes, and it tells a plumber most of what they need to know.

1. Run the kitchen tap for a minute and watch the sink. Does it clear? Two minutes.
2. Run the bathroom basin and shower in turn. Do they drain, or gurgle? Three minutes.
3. Flush the toilet and listen at the nearest shower or floor drain for bubbling or backing up. Two minutes.
4. Walk outside to the gully trap or the inspection opening nearest the house and look at the water level. Five minutes.
5. Write down the date of every blockage you can remember, and what was done about it each time. Three minutes.

If only the kitchen sink is slow, you probably have grease or food waste, and quick fixes for kitchen sink clogs covers that. If several fixtures slow down together, or the same blockage keeps coming back after it has been cleared, the cause is more likely to be in the pipe running under the garden. That is where tree roots and old pipes come in.

Why this one keeps coming back

A pipe blocked by grease or a wipe stays clear once it is cleaned, until the next time you put the wrong thing down it. A pipe blocked by roots does not. Tree roots in drains are drawn to the moisture and nutrients leaking from a drain, and they enter through joints and small cracks. Once inside, they grow into a mat that catches paper and debris. Clearing the line can restore the flow for a while, but unless the point of entry is dealt with, the roots grow back.

That pattern is the main sign. A drain that blocks again within weeks or months of being cleared, in the same place, is behaving like a pipe with something growing in it. It is a different kind of problem from a habit problem, and it needs a different kind of fix.

Why older pipes are more exposed

Many older Australian homes have clay or earthenware drainage pipes, laid in short lengths with joints between them. Over decades, the joints can shift, the ground moves, and small gaps open. Newer pipe materials are jointed differently and are generally more resistant to intrusion, though a poorly made or damaged joint can fail in any material.

Other age-related faults look similar from the inside of the house. A section of pipe that has settled can form a dip that holds water and waste instead of letting it run on, and pipes laid at the wrong fall slow the flow so solids settle. These are not root problems, but they cause the same repeat blockages, and a camera inspection is what tells the difference.

What a camera inspection shows

A drain camera is a small waterproof camera on a flexible cable, pushed down the pipe by a plumber. It lets you see the inside of the pipe on a screen, and it usually records the footage. A good inspection shows whether there are roots, where they enter, whether joints have separated, whether the pipe is cracked or collapsed, and whether there is a dip holding water.

Three things are worth asking for:

1. The footage or still images, so you can see what the plumber saw and keep a record.
2. The location of each fault, measured from a fixed point such as the inspection opening, so repairs can be priced and found.
3. A plain explanation of the options, each with what it fixes and what it leaves in place.

Prices and call-out terms differ between businesses and vary with the job, so get more than one written quote for any work beyond clearing the line, and ask what the quote covers.

The repair options, side by side

None of these is automatically the best. A short length of damage in an otherwise sound pipe may suit a spot repair, while a pipe with many failing joints may justify a larger job. The camera footage should drive the decision.

Who does the work, and who pays

Drainage work in most states must be done by a licensed plumber. Ask for licence details and check them with your state’s regulator, which in Victoria is the Victorian Building Authority, now trading as the Building and Plumbing Commission. Also find out where your responsibility ends. Generally, the pipes inside your property boundary are the owner’s concern, while the main sewer belongs to the water authority, but the boundary point differs by place and by how the property is connected. Your water authority can tell you where the line falls. Check your home insurance policy too, because some policies cover some kinds of drain damage and others do not, and the answer depends on the wording.

The trees

Tree roots do not choose old pipes out of malice, so the long-term fix includes the garden. Planting large, thirsty trees close to a sewer line invites trouble, while smaller shrubs with shallower roots are a safer neighbour. If you are planning to change your garden, building an eco-friendly garden without starting over covers how to choose plants that suit the site, and the same thinking applies to where they go in relation to pipes. If a tree is already the problem, check your council’s rules before removing it, because many councils protect larger or significant trees and require a permit.

Day-to-day habits, briefly

Even with a root problem, ordinary care still helps. Use a strainer in the sink and shower, keep fat out of the drain, and flush only toilet paper. For a wider look at looking after the pipes in your home, maintaining a reliable home plumbing system is a good place to start.

What to do tonight

Look back at your list of dates. If the same drain has blocked more than once in the same spot, put a camera inspection on tomorrow’s to-do list and ask for the footage.

Sources: Building and Plumbing Commission (the Victorian Building Authority’s trading name), plumbing regulatory framework (https://www.bpc.vic.gov.au/plumbers/plumbing-regulation-and-compliance/plumbing-regulatory-framework); your state or territory water authority for the owner and authority boundary (no single page applies nationally); your council for tree protection rules (varies by council).