What causes blocked drains on the Gold Coast?

Tree roots, in older suburbs

If your house was plumbed before PVC became standard, the sewer is probably vitrified clay or earthenware, joined with mortar or rubber rings. Those joints weep a little. Roots find the moisture, work in through the joint, and then thicken into a mat that catches paper and solids.

This is the dominant cause in Southport, Labrador, Ashmore, Benowa, Burleigh Heads, Palm Beach, Miami, Currumbin and the older parts of Nerang. A fig or a camphor laurel within about 30 metres of the line is all it takes.

The tell is a drain that blocks, gets cleared, and blocks again in the same spot six or twelve months later.

Fat and grease, in every kitchen

Cooking fat goes down the sink warm and liquid. It cools on the way along the pipe and sets on the wall like candle wax, in layers, over months. Nothing dramatic happens until the bore has narrowed enough to catch a bit of food scrap, and then the sink stops.

Commercial kitchens hit this much faster than homes, which is why we do a lot of grease work behind the restaurant strips at Broadbeach, Surfers Paradise and Southport.

Wet wipes, in newer estates

In Pimpama, Coomera, Upper Coomera, Pacific Pines, Robina and Varsity Lakes the pipework is modern PVC with solvent-welded joints. Roots very rarely get into that. What we pull out of those lines instead is wet wipes.

Wipes do not disintegrate the way toilet paper does, whatever the packet says. They leave the bowl, which is all "flushable" really claims, then snag on anything rough and knit together into a solid plug.

Cat litter deserves a mention too, because it is designed to clump when wet, which is precisely the wrong property inside a drain.

Damaged pipe, anywhere

Ground movement, tree roots widening a hairline crack, or a shallow line under a driveway taking vehicle loads. Reactive clay soils move seasonally, and sandy canal backfill settles.

A damaged pipe is the one cause where clearing will never be the end of it. If a drain keeps blocking in the same place, the pipe is the problem, not what is going through it.

Silt, sand and leaf litter, in stormwater

Stormwater blocks differently. On bushland-backed blocks in Reedy Creek, Tallebudgera and the hinterland it is leaf and bark load. On acreage it is silt washed off unsealed driveways. In canal estates it is sand migrating into the line through open joints.

Low-lying canal suburbs have the extra problem that stormwater outfalls are tidal, so on a king tide the water has nowhere to go even when the pipe is perfectly clear.

How to tell which one you have

• Only the kitchen sink is slow, getting worse over weeks: grease
• Several fixtures backing up at once: a blockage in the main line
• Blocks every few months in the same place: roots or damaged pipe
• Blocked suddenly with no history, in a newer house: wipes or an object
• Yard floods after rain but drains inside are fine: stormwater, not sewer
• Gurgling when another fixture drains: a partial blockage in a shared line