Toronto is a city on the rise, growing in population every year, as new people from surrounding areas, and further abroad, flood in to call the Six their home. But with a finite amount of space, what this means is that the city’s population is also becoming denser. For developers, this means buying out and tearing down single-family dwellings and small business centres, and building massive, sky-reaching condos. Because they can’t build outwards, they build upwards.

But this isn’t so feasible for the average homeowner. A homeowner looking to expand their living space has one of two options: either tear down the house, and rebuild a taller one; or try and find some space underneath the house. For many homeowners in the GTA, the latter option is the more appealing – and more economical – choice.

As opposed to new construction, many homeowners in Toronto prefer major house renovations that include basement lowering, or underpinning. It’s less expensive than other expanding projects, it’s less disruptive and it improves the home. Most existing dwellings have about a 7.5’ high basement, but if you were to add ducts, installed under the joists, you could add a fairly sizeable amount of space, which can be used as storage. This frees up other room in your home.

It’s an imaginative approach to home expansion, and one that we’ve seen embraced by many Torontonians. It might also improve the integrity of your home; for those houses with mouldy or dank basements, a refortification of the basement isn’t just about living space, but about creating a healthier, longer-lasting foundation.

Lowering your basement has its obvious advantages, and can add value to the house, but there are many possible plumbing issues – or, at the very least, considerations – that naturally arise when you undertake a large renovation project like basement lowering. In this post, we’ll discuss a few of the particular plumbing problems you might come up against, and precautions you might want to take.

If some of the following material seems confusing, don’t worry: plumbing is an intricate and technical discipline, and it can be difficult to grasp sometimes without real-life visual aids. If you are curious to learn more, click here for a helpful article about basement drainage, or give us a call. With that in mind, let’s do our best to explain how basement lowering affects your plumbing.

plumbing toronto

Drain Inspection

Before starting any major project involving the basement, Mister Plumber recommends camera inspection of the underground main drain and sewer pipe. Drain inspection is important when lowering your basement since it lets us know exactly what we’re dealing with – it lets us know what state the existing pipes are in. As with anything else pertaining to your basement – electricity, foundation, etc. – contractors want to inspect before they start work. As we’ll see, there’s a chance during underpinning that your drains and pipes will get moved around.

Sewage Pump Installation

Depending on the depth of the pipe, your drain and plumbing might require one of a few different approaches. For example, if you plan on having a new concrete level below the existing pipe, a sewage pump must be installed, in order to serve the plumbing fixtures in the basement. All drain stacks from the main and second floor have to be re-routed under the ceiling or along the foundation wall to the front, with a proper slope, and connected to the main building drain the way all sewage flows by gravity.

In the pictures above and below, you can see drainpipes that serve their above basement fixtures, as well as their connection to the main pipe with a sewer clean-out.

plumbing toronto

When You Don’t Need a Sewage Pump

Not all underpinnings require a sewage pump. If the sewer line is already deep enough, no sewage pit and pump are required. In such a case, wastewater flows by gravity and it doesn’t depend on an electronic device (pump) and electricity. Although it doesn’t work out this way in every home, it’s nice when it happens, since there’s no noisy pump to activate.

An inexperienced plumber might not know when not to install a sewage pipe, which is why you need an experienced expert on hand during underpinning. You can call us for a quote anytime, and we’ll be more than happy to chat with you about your plans, project and ultimate aims.

Backwater Valve Installation

Just because you don’t need a sewage pump, doesn’t mean you don’t need any form of protection. In order to protect the plumbing fixtures in your basement, it is very important to install a backwater valve. Backwater valves prevent outbound water from re-entering your home, therefore saving your basement from a lot of nasty, noxious sewage. Luckily, in Toronto, there are subsidy programs in place for backwater valve installation.

In cases where a sewage pump is installed, however, there is no need to install a backwater valve, as the discharge pipe leading from the pump is protected by a check valve.


Waterproofing your newly underpinned basement is a crucial step in ensuring that your investment is properly handled. The last thing you want is to spend a good chunk of change lowering your basement, only to have a summer flash flood ruin your hard work. Elsewhere on our blog we’ve discussed why basement floor drain is so important but exterior and interior waterproofing are equally important to preserving the integrity of your basement.

There are many other plumbing codes that are important during large home alterations like underpinning, but they’re too numerous and complex to cover in a single blog post! Hopefully these few considerations have given you a good idea of what underpinning entails when it comes to plumbing.

To get the job done right, call Mister Plumber to get the best solution for your renovation project. We have been a part of countless renovation projects, and there is nothing we love more than seeing a homeowner’s vision come to life, especially when their plumbing is installed sturdily, correctly and protectively.

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