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Plumbing or Waterproofing Problem? How to Diagnose Basement Water Issues

Basement water issues can cause significant damage to your home and be a source of stress for homeowners. Identifying the root cause of these issues is crucial to finding the right solution. In many cases, the problem can be traced back to either a plumbing issue or a waterproofing issue. In this comprehensive guide, we will help you diagnose the cause of water in your basement and provide preventative measures and maintenance tips to avoid future problems.

Table of Contents

Identifying the Source of the Problem: Plumbing or Waterproofing?

When you notice water in your basement, it’s essential to determine if it’s a plumbing issue or a waterproofing issue. Here are some key questions to help you identify the source of the problem:

How long has the problem been going on?

If the weather has been dry for weeks and you notice water in your basement, it’s likely a plumbing issue. Foundation leaks are usually weather-related. If the soil surrounding your home is wet, the water could be due to a foundation crack. If the soil is dry, the water is likely coming from another source within your home.

Diagnose Basement Water Issues: Plumbing or Waterproofing?
Diagnose Basement Water Issues: Plumbing or Waterproofing?

How much water are you seeing?

The amount of water in your basement can help you determine if the issue is due to a foundation leak or a plumbing problem. An obvious pool of water near a floor drain or a damp corner at the base of your wall might indicate different causes.

Is the appearance of water in the basement related to the use of fixtures in your home?

Pay close attention to the appliances you were using at the time of the leak and note any irregularities in water volume. If your dishwasher is leaking into your kitchen wall, that water is likely to end up in the basement.

Have you ever had a sewer backup?

A previous sewer backup could indicate recurring issues, such as tree roots or faulty pipes, causing blockages in the water pipes.
By answering these questions, you’ll have a better understanding of whether you’re dealing with a plumbing or waterproofing issue.

The Importance of Regular Plumbing and Waterproofing Maintenance

Preventative measures and maintenance can help you avoid water issues in your basement. Here are some tips to keep your plumbing and waterproofing systems in good condition:

  1. Inspect your plumbing system regularly: Schedule routine plumbing inspections to identify and address any potential issues before they become significant problems.
  2. Clean your gutters and downspouts: Ensure your gutters and downspouts are clear of debris to prevent water from overflowing and causing foundation damage.
  3. Maintain proper grading around your home: The ground should slope away from your foundation to prevent water from pooling near your home and causing leaks.
  4. Install a sump pump: A sump pump can help remove excess water from your basement and protect your home from potential water damage.
  5. Seal foundation cracks: Inspect your foundation regularly and repair any cracks or openings to prevent water from entering your basement.

How to Troubleshoot Plumbing and Waterproofing Issues

If you suspect you have a plumbing or waterproofing issue, follow these steps to troubleshoot and identify the problem:

  1. Inspect your home’s exterior: Look for signs of foundation damage, such as cracks or bulging walls, and check for proper grading and gutter function.
  2. Examine interior walls and floors: Look for signs of water damage, such as discoloration, peeling paint, or mould growth.
  3. Check your plumbing system: Look for leaks, corrosion, or other signs of damage to your pipes and fixtures.
  4. Monitor your water usage: Keep an eye on your water bill and note any sudden spikes which may indicate a leak in your plumbing system.
  5. Consult a professional: If you’re unsure of the cause of the water issue, call a trained waterproofing or plumbing professional to assess the situation. Provide as much information as possible about the history of work performed in your home and any previous water-related issues.

Case Study: A Unique Water Issue Scenario

To illustrate the importance of properly diagnosing a basement water issue, let’s explore a real-life example. One of our top consultants was called to provide a free estimate for a home that exhibited many of the previously mentioned scenarios.
Upon entering the basement, the estimator noticed litres of water pouring down to a lower area. The homeowner mentioned that the issue had started after recent rain and snow melt and that it wasn’t the first time. Additionally, the homeowner had experienced plumbing issues in the past.
The floor drain had water up to the basement floor level, and the toilet, located just back from the floor drain, had water almost to the top of the bowl. The toilet’s water supply had been shut off just 10 minutes prior.
Our estimator inspected the exterior foundation and noticed it had already been waterproofed. Given the age of the home (90 years), it was likely that the previous waterproofing contractor had installed weeping tile connected to an old rainwater pipe from the eaves (an old storm line). In this particular neighbourhood, the storm lines are often connected to the sanitary lines via the floor drain.
The sanitary line was blocked downstream of the floor drain and toilet, and the weeping tile was bringing water into this combined system. In this unique situation, there was so much precipitation and snowmelt entering a blocked line under the basement floor that the water had nowhere to go, resulting in extreme amounts of water being forced out of the pipes and rising up from beneath the floor.
In this case, it was clean water (outside rainwater) backing up dirty (sanitary pipes) and entering the basement. Therefore, it was strongly recommended that the homeowner consults with a plumber first to clear the blocked lines.


Finding water in your basement can be a sign of a more serious issue. By following the tips provided in this guide, you can better diagnose whether you’re dealing with a plumbing or waterproofing problem. Remember to perform regular maintenance and inspections to prevent future water issues in your basement. If you’re unsure about the cause of the problem, consult a professional to ensure the issue is resolved properly and efficiently.

Basement Waterproofing FAQ

Most frequent questions and answers

The five most common plumbing problems are:

  1. Leaky faucets: Dripping faucets are a common issue often caused by worn-out washers or cartridges that need replacement.
  2. Clogged drains: Blocked drains in sinks, showers, or bathtubs can occur due to a buildup of hair, soap scum, or other debris.
  3. Running toilets: A continuously running toilet can waste a significant amount of water and is usually caused by a faulty flapper valve, float, or fill tube.
  4. Low water pressure: Reduced water pressure in faucets or showers can be caused by sediment buildup, pipe corrosion, or issues with the water supply line.
  5. Burst pipes: Pipes can burst due to freezing temperatures, corrosion, or high water pressure, causing significant water damage to your property.

No, a waterproofer is not a plumber. While both professionals deal with water-related issues, a waterproofer specializes in preventing water intrusion in building structures, such as basements or foundations. A plumber, on the other hand, focuses on the installation, maintenance, and repair of water supply and drainage systems within a building.

The responsibility for waterproofing typically falls on the property owner, who must ensure that their building is adequately protected against water intrusion. In new construction, waterproofing should be carried out by qualified professionals according to building codes and industry standards. For existing structures, the property owner is responsible for routine maintenance and repair of waterproofing systems to prevent water damage.

Waterproofing is not a structural issue in itself, but it plays a crucial role in protecting a building’s structural integrity. Inadequate or faulty waterproofing can lead to water infiltration, which can cause damage to the building’s foundation, walls, and other structural elements. Over time, this damage can compromise the stability and safety of the structure.

Signs that waterproofing is failing or inadequate include:

  1. Damp or wet spots on walls, floors, or ceilings.
  2. Musty odours or mould growth.
  3. Efflorescence is a white, powdery substance that forms on surfaces due to moisture evaporating from masonry materials.
  4. Peeling or bubbling paint and wallpaper.
  5. Cracks in the foundation or walls can indicate water infiltration.

If you suspect that your waterproofing is failing or inadequate, it’s crucial to consult with a waterproofing professional to assess the situation and recommend appropriate solutions.


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