How To Fix A Broken Pipe Under The House

Ever wondered how to determine whether there could be a water leak under your house and the initial steps to take if you discover such a leak and strategies on how to fix it?

According to data from energy services providers and the Australian Bureau of Statistics, the average Aussie can expect to move house 13 times over the course of their lives.

Moves to and from rental properties account for the bulk of home relocations, with an average of four to six moves being made as a result of a new home purchase. And while pre-purchase pest and building inspections are commonplace, few people think to get inspections of the pipe network often buried beneath the concrete slab supporting their new home.

Even if you’ve lived in a home for years, the vitally important web of water and drainage pipes that keep your castle functioning can become blocked or broken over time and begin leaking. The repercussions of a busted water pipe under a house can be incredibly damaging for the foundations and structural integrity of the building if repairs are not undertaken quickly.

This article will identify ways for you to determine whether there could be a water leak under your house, the initial steps to take if you discover such a leak, and details on the most common strategies for repair.

So, follow this guide on how to fix a broken pipe under your house.

What is a slab leak?

A slab leak is an industry term for a leak within the waterline piping below a home’s concrete floor, and they can occur in homes and buildings of all ages. Broken water pipes under your home can cause irreparable damage to foundations and cost tens of thousands of dollars to repair. The extent of the damage can be exacerbated by certain types of soils (expansive soils) which absorb greater quantities of water and expand, often causing slabs to lift and crack (see our article The best ways to repair sewer pipes and collapsed drains under slabs).

The more quickly an underground water or sewer leak is detected and repaired, the lower the final cost is likely to be, so being aware of the early signs of a slab leak can save homeowners from potentially devastating consequences.

9 Signs of a water leak under the house

While water leaks under house slabs are notoriously good at remaining hidden from the untrained eye, knowing what to look for and regularly checking can help you get on top of things before they do too much damage.

Early and common signs of a slab leak are:

Early and common signs of a slab leak are:

  1.  Wet areas of grass beside the home’s exterior walls
  2.  Wet or damp patches of carpet or moisture on internal flooring
  3.  Mildew or mould under carpets, rugs or at the base of drapes
  4.  A musty odour in certain rooms
  5.  The sound of running or rushing water even when all outlets are turned off (you may have to get down and put your ear against the floor to hear such a leak, which indicates a leak in the pipes entering the house)
  6.  Warm spots on the floor (walk the floor without shoes or socks in the line from the hot water system to relevant outlets as this can indicate a leak in a hot water pipe)
  7.  Unexplained increases in your water bill
  8.  Low water pressure
  9.  Rising damp on walls when there has been no significant rain

If there are no obvious signs, but you still suspect there are broken or leaking water pipes under your slab, you can simply turn off all water outlets (including washing machines, dishwashers, toilets and taps) then take a reading of your water meter (usually located at the front boundary of your property).

After 15 minutes of non-use, go and check the meter again. If the number has increased, water is being consumed and is leaking from your pipes – so you are losing (paying for) water you are not using.

More serious signs of structural damage from water leaks under slabs

Sewer line leaks can be a bit more difficult to spot but they can be just as damaging, particularly in areas with expansive soil. Expansive soils contain minerals that absorb water (such as clay soils) which can increase the soil volume by up to ten per cent, which is why leaking sewer lines under slabs can be so serious.

If slab leaks have been present for some time or your property sits on expansive soil, some of the more ominous signs to look for are:

  • cracks in walls leading up from the floorcracks in tiles or concrete flooring
  • raised (dome-shaped) areas of flooring
  • warped timber boards.

These signs indicate there has been significant damage to the home’s foundations and you should seek advice from a professional builder or engineer before proceeding with repairs.

What to do if you have got a leaking pipe under your house

Once you’re sure there is a leak there are a few simple next steps to take.

1. Establish the location of the leak

The first step is to establish where the leak(s) are located. If you see or hear water in one particular section of your floor, you might be able to take an educated guess, but there is no guarantee the offending pipe will be located right beneath the wet patch you’ve noticed on your carpet. Water is notorious for pooling in empty or low-lying cavities so the actual break or crack could be some distance away. You won’t be popular if you assure your wife you can repair the pipe yourself and cut up the concrete in her new bathroom floor – only to find the water’s coming from a leaking join two metres along the line.

Finding the exact location of leaking pipes beneath a house slab usually requires the help of a professional with specialised listening devices, CCTV cameras and other leak detection equipment. To detect leaks in the small pipes that bring pressurised water to your home, the water is often turned off and air is pumped into the lines to force out the remaining water. This allows the plumber to listen for escaping air from the damaged pipe.

2. Arm yourself with numerous quotes and information

Once the presence and location of a leak have been confirmed, the next step is the repair. If the leak is outside the perimeter of the slab or near the edge, and you know a bit about basic DIY plumbing, you might be lucky enough to be able to reach and repair it yourself without too much trouble.

But if the leak is deep under your house slab, you would be best advised to consider a professional repair to ensure the structural integrity and insurance cover of your home are not compromised. You should get a range of quotes from different types of pipe repairers, and you should ask each of them as many questions as possible so they can advise on the pros and cons of their particular repair strategy in relation to your particular job.

Just like doctors, whilst all plumbers know the basics, they’re not all experts in all things plumbing. Some specialise in new builds, some in water supply systems, some focus on gas fitting or roofing and some deal in mechanical services. So if you need to repair drain pipes under your house slab, you need more than just an everyday, all-round plumber who might only deal with similar under-slab leaks a handful of times each year. You need to ensure you deal with tradespeople with established reputations as experts in things like pipe relining, drainage and pipe clearing under slabs.

When you are talking to each of the people quoting the job, pick their brains about possible options. For example, if the tradesperson quoting is a specialist in CIPP relining methods, ask them whether a traditional excavation and replacement might work better for you, and if not – why.  This way you will get to hear all the potential negatives of each strategy, which will equip you to ask better questions and make a more informed final decision. Once you have all the information and options, you are ready to consider which repair strategy is best for you.

3. Decide on the best repair strategy for your situation

There is no ‘one-size-fits-all’ best option for repairing pipes under a slab. If you’ve got a holiday home at the beach you can hang out in for a month, for example, or if you were already considering a complete kitchen and bathroom make-over, then excavating and replacing all your water and sewer pipes might not be such a bad thing. Carefully consider everything you’ve learned, taking into account all the additional costs for things like temporary accommodation you might need, having to buy takeaway for two weeks or re-laying the expensive new floor tiles your wife is likely to pick out. And don’t forget to factor in less tangible elements, like the joy of living with your mother-in-law for a month. This way you will avoid any unpleasant surprises when you add up the total costs after the job is done.

In the next section we identify the most commonly used strategies for fixing broken pipes under a house.

The main methods of repairing broken pipes under house slabs

There are three main approaches to repairing leaking drains under house slabs. You should ensure you have obtained an inspection/quotation from at least one specialist from each area.

Drain Camera Inspection

Nuflow technicians carrying out a CCTV inspection on a broken drain pipe under a house.

These approaches are:

  1. replacing broken pipes by cutting the slab, excavating the dirt and damaged pipes, installing replacement pipes and joins and then reinstating your concrete slab and flooring
  2. re-routing your plumbing to be external to the house slab
  3. relining broken pipes with advanced composite resin and fibre CIPP compounds which are cured to form a strong, new, crack-resistant pipe inside the old one without the need to excavate.

Choosing the right pipe repair strategy for your situation could potentially save you thousands of dollars in the long run. Depending on your specific circumstances, some of these alternatives can be surprisingly affordable and can save a considerable amount of stress, disruption and inconvenience for property owners.

A full explanation of the advantages and disadvantages of each of these strategies can be found in our companion article, The best ways to repair sewer pipes and collapsed drains under slabs.

How much does repairing a slab leak cost?

Repairing drains under a house slab doesn’t come cheap. Whichever option you finally go with, it is unlikely you’ll get any change from $1,000 and depending on the extent of the damage, could be anywhere from $6,000 to $8,000 – so shopping around and becoming as informed as you can is vital.

Having a drain inspection prior to purchasing a new home can help avoid the cost and heartache of finding collapsed drains under the slab a few months down the track. If problems are found, it can also enable you to negotiate on price to ensure you have the funds to easily address the issue.

But at the end of the day, if you do discover there are water leaks under your house slab, don’t panic. New pipe repair methods, such as CIPP relining, mean affordable solutions that don’t destroy your home or lifestyle are now available. Simply consult a range of experienced tradespeople who are experts in the three main methods of drainage and pipe rehabilitation identified above and who deal with similar issues to yours every day.

Get their advice on what method is best for you and then simply decide on a strategy you and your family can emotionally and financially manage.

If you’d like a quote on fixing a slab leak from your local Nuflow pipe repair specialist, visit our contact page.


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