Today we’re going to tell you all about running traps. Our Toronto plumbing and drain professionals have run into these devices in a number of properties throughout the City. They are outdated ticking time bombs that need to be replaced as soon as possible.

They are an outdated plumbing device that was built into a lot of buildings before the 1950s. These have caused many plumbing problems in old homes. You’ll find people refer to these traps by many names, but not all of them are correct:

  • Running traps
  • Sewer traps
  • Main drain traps
  • Building traps
  • Building P traps
  • Main sewer line trap

What Does a Plumbing Trap Do?

Traps reduce the risk of sewer gases or small rodents coming back up through the sewer. There are many types of traps in plumbing and plumbing traps are used all over your property including:

  • Beneath your sink
  • Built into your toilet
  • Beneath your toilet/shower/tub
  • Often hidden in your walls/flooring

They are named traps because they trap a bit of water in the pipe creating a seal between the sewer and the building. There’s nothing wrong this blocking the sewer from your home in such a way, in fact it’s want you want.

A running trap as we are discussing here was a common house sewer trap method, essentially a trap was placed into a pipe with no way of cleaning it out. A lot of the time these types of traps become clogged or end up with obstructions that will lead to corrosion at some point.

corroded house sewer trap found inside of a home

Corroded cast iron trap – courtesy

Usually the result is raw sewage will back up into your property, even causing flooding; whether it’s your home, place of business, or a property you own this is not something you want happening.

What’s Wrong with Running Traps?

Running traps are still found on many buildings that have yet to have them removed, however, international plumbing code forbids the installation of running traps on any new buildings. The reason is that nowadays there are better sewer traps that can be installed instead of the running trap method.

Why are running traps banned?

  • Typically made from inferior materials (clay or terracotta)
  • Prone to breaking or bursting due to lack of ability to handle pressures and/or build-up
  • Sometimes they just break apart from the pressure of the soil above them
  • Sewer trap cleaning was virtually impossible
  • Clogs are inevitable when they cannot be cleaned
  • Much better methods are available to solve the same problem

The most important reason is that cleaning out these traps was impossible, making clogged sewer drains inevitable. In fact, when facing a clogged running trap the typical way of solving the problem is digging up the ground to get to the trap and replacing it.

Luckily, new sewer traps are easier to clean, and render the old main drain traps obsolete. The only thing they can do for a building now is cause problems. That’s why we recommend getting rid of them wherever they are found.

Why Did Plumbers Install These?

Usually, sewer main traps were used when the sewer line also linked into the storm drains. They were meant to prevent certain problems, like rats or snakes coming through the pipes, or seepage of unwanted gases into a home. When these traps were first installed plumbers weren’t aware of the potential problems they would cause in the future.

In any event, they decided this was the best solution for the problem. But as we’ve come to learn they are known to become clogged easily. Nobody wants a clogged main drain, when your waste has nowhere to drain it ends up back in your home or building. Not very nice.

What To Do If You Have a Running Trap?

So what do you do if you discover that your building still has a main trap? We recommend sewer trap replacement as soon as possible. Call up your local plumber and have it replaced. Since these traps are nearly impossible (and sometimes actually impossible) to clean out, sooner or later you are going to experience a sewage back-up.

We replace all running traps, either with a PVC trap featuring a clean-out or in many cases a proper backwater valve is hooked up to prevent back-flow of sewage. If you are unsure of whether your home or office has a main drain trap, call a plumber to come out and inspect your drain system. Main traps can be identified by any skilled plumber.

Replace Your Running Trap Now

Replacing a trap can be a fairly simple or a more complex process, depending on the location of the trap and the materials covering. Sometimes a trap is just underneath a basement that has a dirt floor. These are very easy to dig up and replace.

However, if the trap is underneath several inches of concrete, the replacement process takes a bit longer. Either way, clogged or broken main traps are a major cause of sewage back-up and basement flooding.

Usually the trap is just removed and replaced with a more suitable piece. PVC trap installation is a service we carry out typically when replacing these devices. They come with a clean-out so we can easily access and clean the trap out in the future.

The process itself isn’t very complicated; the hardest part is the digging. Upon digging up traps, we often find that the piece itself has become rusted and developed holes, splits, and has been leaking sewage into the soil. This causes environmental problems, as well as being a health and safety concern.

Raw Sewage Is Always An Uninvited Guest

Raw sewage backing up into your building can cause a ton of damage. It can ruin whatever you have in your basement, and even cause your building to become condemned on the basis of safety. If you are the victim of constant sewer clogs and basement flooding, you should definitely look into having your main trap removed.

This work is a specialty of ours, so give us a call if you need any assistance.

Andrew Olexiuk - Your Toronto Plumbing Expert
Andrew Olexiuk - Your Toronto Plumbing Expert
Andrew has over 20 years of experience as a plumbing contractor. He is co-owner and operator of Absolute Draining & Plumbing, a professional plumbing company serving residential & commercial properties across the Toronto, Ontario region.
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Showing 3 comments
  • Toichi

    If the house trap is removed then what about gases from the main sewer line?
    Houses are built nowadays very air tight and if a shower trap dries up then you have a problem.
    If cleaning the trap is the main reason not to install them then, why not just simply keep cleaning it a priority in their planned location?

    • The Absolute Draining & Plumbing Team

      Of course the house trap needs to be replaced with an appropriate device to ensure your plumbing is functioning. The problem with these running traps is that cleaning them is simply not possible, so eventually they will become blocked. Replacing with an appropriate trap with clean-out access for instance is a solution. If you’d like to discuss specifics or have a project in mind feel free to give us a call and we’ll explain the most appropriate device for your project.

  • David Chiarot

    I have 2 mushroom vents on my front lawn. I also think I have a sanitary and a separate storm line. Does that mean there is a trap on each line.

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