Dig or reline? What’s the best fix for a blocked sewer?

If your sewer’s ever been blocked, you know it’s not pleasant. Your bathroom is permanently on the nose, and you’re constantly plunging the toilet just to get it to flush properly.

But as unfortunate as the smell and inconvenience are, the fact is, they’re not the worst of it. Not even close. Any overflow of bacteria-ridden backwash flooding your bathroom floor is a genuine health hazard. And if your sewer’s showing even the slightest sign of blockage, an overflow is a very real possibility.

What causes most sewer blockages in Sydney?

Tree roots

If you’re in Sydney, the condition of your sewer is largely dependent on the number of trees near your sewer system – especially fig trees. Those buggers are particularly aggressive and numerous in the Sydney area. They grow fast and can easily crack old earthenware pipe work with their root systems. And unfortunately for Sydney-siders, earthenware pipe work was very common for new homes in Sydney right up until the early 1980s.

Because earthenware sewer pipes were installed in sections and their joints sealed with mortar mix or O-rings, it was never a watertight option. As time passes, the porous nature of the mortar mix allows tree roots to enter the pipe system in search of water. The accumulation of tree roots initially obstructs the flow within the pipe eventually leading to blockages. The pressure of tree roots puts further pressure on the pipe system causing it to crack and dislodge eventually leading to complete collapse.

From the early 80s onwards, PVC pipes have been used instead of earthenware. It’s better, but by no means a silver bullet. Like earthenware, it all comes down to the joins and the way in which the pipe work is supported: The joints need to be properly glued and the pipe work supported during the backfill process. If the PVC installation is not well executed tree roots will enter via the joins causing weakness in the pipe system and further opportunities for root intrusion.

Flushing the wrong stuff

Toilets and toilet pipes get blocked when people flush the wrong things. Like wipes, food scraps, paper, rags, cans, bottles, grease and fat. You should never flush any of that stuff down the toilet.

Putting the wrong stuff down the sink

Wastewater pipes from sinks, basins and laundry tubs can get blocked if people put food waste – especially tea leaves or hot fat – and other rubbish down them. (Wondering why hot fat blocks the pipes? It’s because it solidifies when it cools.)

What’s a better fix for sewer blockages? Relining or digging?

Unfortunately, given that you’re reading this article, chances are it’s already too late for you to avoid a blockage. That horse has already bolted. But you do still have the power to choose the best fix for your blockage.

The question is, what’s the best solution? What will give you the best bang for your buck?

You have two options: Reline your existing pipes or dig them up and replace them.

Trenchless pipe relining

How does trenchless pipe relining work? First, your reliner will assess the damage by putting a CCTV camera down the drain. This will enable them to determine if relining is a suitable solution.

Assuming relining is possible, your reliner (if using the inversion method) will clear the drain using a high pressure water jet, then cut a seamless, flexible textile liner to length, impregnate it with environmentally safe resin, and insert it into the drain using compressed air. Finally they’ll pump hot water through the liner to help cure the resin more quickly. (It’ll be ready to use as soon as the resin cures – usually about 4 hours.)

And that’s it! The inside of the pipe is now completely lined. You have an entirely new pipe inside the old one. No joins, no leaks, no weaknesses. This ‘pipe within a pipe’ is 100% watertight, stronger than PVC pipe, and has an increased flow rate compared to most existing pipes.

Pros

  • More effective protection from root penetration than newly installed PVC or earthenware pipes.
  • No digging, so very little mess, no ruined gardens, paths and driveways, and no cost, time and hassle to restore your property and landscaping.
  • No reinstatement costs means that it can be cheaper than digging depending on what’s above the ground.
  • It’s fast! Most jobs can be completed within a day – without the mess and noise of excavation.
  • You will receive a 20-year guarantee.
  • You can preserve heritage buildings and trees.
  • Relined pipes have improved flow.
  • 50-year life expectancy.

Cons

  • It can be expensive due to the cost of materials and equipment required, such as robotic cutting equipment.
  • Roots can grow back on the unrelined sections.
  • Relining may not be possible: it is not possible to reline pipes with a diameter less than 40mm e.g. pool piping.

Digging

The traditional way to fix drains is to dig them up and replace the damaged sections. This is achieved by first locating the problem in the pipe work. To ensure that electrical and telephone wires are not hit during the excavation process Dial Before You Dig should be contacted to verify the location of services. If excavation is required in a public area such as a footpath or road, council fees will apply.

The location of the damaged pipe work will determine whether a jackhammer or road saw is required to remove paving or concrete. The ground can be excavated either by hand or using an excavator. The pipe work is replaced using PVC and joined to the exiting sewer using glue. The excavated area is then back-filled with 10mm crushed blue metal. The waste is removed to a skip bin.

Pros

  • Digging can be a cost effective option if the sewer is close to the surface and is easily accessible.
  • Digging is the only solution for repairing:
    • Pipes with a diameter of less than 40mm e.g. pool piping;
    • Storm water lines with 90º hard edge radius’ and upwards

Cons

  • Takes days
  • It is messy and noisy
  • If too close to your home it can affect its foundations
  • Usually only 1-year guarantee
  • PVC can still allow tree roots to re-enter if not installed correctly
  • Services such as phone lines, electrical lines or main sewer lines can be disturbed
  • Can be expensive if:
    • Digging under concrete, retaining walls or paving;
    • Skip bins are required to remove waste;
    • Council permits are required for excavating public areas;
    • Services such as phone or electrical lines are disturbed

Which should you choose?

It’s horses for courses, really. If the blockage is located close to the surface and not underneath something expensive or precious, digging is probably your best bet.

But if the blockage is under paving, a garden, a retaining wall, your bathroom floor, a road, a driveway, a path, or something else equally expensive to rip up, relining is definitely the way to go.

Just make sure that if you choose relining that you do it before the pipe work collapses otherwise you will have no option but to dig.

Either way, you should always choose a trained reline installer. The best relining technology in the world is Brawoliner, and they train their operatives.