How leaking water pipes can wreak havoc on a home’s foundations

Cracked pipes, blocked gutters and broken sewer lines are a surprisingly common cause of the foundation issues that can affect properties. Put simply, when the ground becomes oversaturated and waterlogged, the soil is weakened and loses strength, which can result in structural issues.

For homeowners, the best way to avoid the costs of repairing foundation issues is to regularly check the ground around your home for damp, waterlogged or subsided areas and act immediately if there is a suspected leaking pipe or drainage issue. It’s also recommended that you look out for the warning signs of foundation issues, such as internal and external wall cracks, uneven floors and misaligned doors or windows.

Different types and locations of pipes

When it comes to maintenance of water, stormwater and sewer pipes, there are some things to be aware of.  Mains water supply, stormwater and sewerage networks are all separate systems, with each designed to meet different needs. Sewer pipes are usually smaller in diameter than stormwater pipes, but can be the same size.

Typically, homeowners are responsible for all of their own property’s pipework within the boundary, subject to the form of title of their property, as well as the pipes leading up to and including the water meter connection. Local councils are typically responsible for the stormwater network that extends beyond the boundary, and the various utility authorities are responsible for the water meter, water mains and sewer pipes that lead to or away from the property. That means the onus is on homeowners to not only fix a leaking or blocked pipe on their property, but also to pay for any excess water wasted as a result.

Signs of water leakage

A hidden or concealed leak can be difficult to spot, as water slowly seeps into the ground, sometimes over a long period of time, before there are any signs of structural issues. This was the case when widespread wall cracks appeared in a heritage-listed Sydney home. The four-bedroom property was built on highly reactive clay soil which became oversaturated due to moisture from the broken sewer and stormwater under the home.  It was suspected that the leaking water had been ongoing for as long as a decade.

Before the home could be re-levelled, the foundation ground first needed to be improved  to prevent further settlement and damage. Using Teretek® resin injection, Mainmark was able to strengthen the clay ground and achieve the necessary amount of lift to bring the home back into alignment.

Another example of structural issues caused by sodden ground occurred at a Sydney home where a modified rainwater downpipe outside the patio area occasionally flooded, washing away underlying soil. Over the course of 18 months, the owners noticed the patio floor was sinking and cracks were starting to appear on the walls.

The poor drainage system needed to be replaced before the patio slab could be returned to its original position, rectifying the alignment and functionality of doors and windows. Teretek® was injected through a series of small keyholes, instantly filling the voids that had formed under the patio and returning the structure back to level without impacting the repaired stormwater drain pipe and a sewer main located underneath the slab.

Common causes for leaking pipes

There are a number of other external reasons that can cause pipes to crack and leak, such as invasive tree roots, overflowing stormwater during heavy or prolonged rain, or the presence of older, clay pipes.

  • Invasive treet roots

Tree roots can enter pipes through tiny fractures or small gaps in search of water, especially during dry spells. Once inside the pipes, they continue to grow, damaging pipes and causing blockages. Tip: understand the tree root system and the projected mature height of the tree and plant at an appropriate distance from foundations, driveways, patios, footpaths. Your local arborist, geotech and structural engineers can best assist to guide you on tree planting guidelines.

  • Broken clay pipes

While PVC or plastic pipes have been used in Australia for more than 40 years, many older homes still have clay or terracotta pipes in place which are liable to leakage at segment joints, and other wear and tear over time due to ground movement, creating holes, cracks, and eventually breaks in the pipes. Clay pipes are also particularly weak against root intrusion. Tip: consult a licenced plumber to check the current health of pipes on your property.

  • Stormwater overflow

In wet weather, rainwater can overwhelm the stormwater network and spill over into the sewer system, which may cause sewage to be overloaded, back up and potentially overflow into the ground. Overloaded stormwater drainage systems can also result in over land flow and ponding in low lying locations, that may concentrate water to foundation soils and cause structural issues. Tip: make sure stormwater pipes do not drain rainwater from your roof gutters into the sewerage system and that your stormwater disposal system is regularly maintained and cleaned to avoid being overloaded and over flowing.

Preventing structural issues

For homeowners, it is important to watch for signs of leaking pipes or drainage issues before ground subsidence begins to impact your home’s foundations. Pay attention to slow-draining sinks, toilets or showers, ensure rainwater is not directed into stormwater pipes and check your water bill for unusually high levels of consumption.  In extreme situaltions sink holes can appear at the surface where the subsurface foundation soils are being washed away by leaking services.

If a leak is detected, the first priority is to have it fixed by a licensed plumber as quickly as possible to avoid losing excessive amounts of water or having uncontrolled stormwater or sewer disposal, and before it can impact the home’s foundations.

For advice on the best way to remediate structural issues that may occur as a result of underground water leaks, contact Mainmark on 1800 623 312 in Australia, on 0800 873 835 in NZ, or visit www.mainmark.com.


Laurie Andrews MainmarkBy Laurie Andrews

Laurie Andrews is Mainmark’s Business Development Manager for NSW & ACT. Laurie is a qualified civil and structural engineer with nearly 30 years experience working in the construction and engineering industry.