High Water Bill Mystery: 6 Sneaky Plumbing Leaks That Could Be the Culprit

A sudden spike in your water bill often comes with no clear explanation. You’re using water like you always do, but somehow the numbers keep climbing. Before blaming your dishwasher or morning showers, it might be time to look behind the walls, under the floors, and in the corners you rarely check. Hidden plumbing leaks are some of the most common—and costly—culprits behind rising water bills. The worst part? Most of them stay out of sight until the damage is done.

Let’s walk through six types of sneaky leaks that may be quietly driving up your costs and how to catch them before they get worse.

Sneaky Plumbing Leaks That Might Be Raising Your Water Bill

1. Leaky Toilet Flappers

Toilet leaks are deceptively quiet. A misaligned or aging flapper valve can cause your toilet to run intermittently or continuously, wasting hundreds of litres a day.

Since these leaks don’t always produce sound, they often go unnoticed. One of the easiest ways to check? Drop a few drops of food colouring into the tank. If the colour appears in the bowl without flushing, water is slipping through when it shouldn’t be.

2. Dripping Faucets (Especially in Unused Areas)

A dripping tap in the guest bathroom or a hose bib outside may not seem urgent, but over time, even a slow drip adds up. Faucets that leak once every second can waste more than 11,000 litres of water annually. That’s a lot of water (and a lot of money) literally going down the drain. Take a walk through your home occasionally to check for small drips in rooms you rarely use.

3. Underground or Slab Leaks

Some of the most damaging leaks happen where you can’t see them, like beneath your home’s foundation. These underground leaks can occur in water lines running beneath concrete slabs and are difficult to identify early on.

Watch for signs like unexplained damp spots on floors, musty smells, sudden mould growth, or parts of the floor that feel unusually warm. If you suspect an issue, professional leak detection is a must.

4. Leaking Water Supply Lines

Your washing machine, dishwasher, and refrigerator all depend on water supply lines that are tucked behind walls and cabinets. If these lines develop even a pinhole leak, it could go undetected for weeks. Look for bubbling paint, stains on drywall, warped flooring, or mildew smells near appliances. These clues often point to a slow leak behind the scenes.

5. Faulty Water Heaters

Water heaters can leak in ways that aren’t immediately obvious. If a valve inside the tank fails or corrosion develops, water may slowly escape without any loud drips or puddles in plain sight.

One of the first signs homeowners notice is a drop in hot water pressure or water that doesn’t stay hot for long. In some cases, you might see rust forming on the tank or find a damp area on the floor near the base. These aren’t just maintenance issues; they often point to internal problems that can waste water and lead to a bigger breakdown if ignored.

Checking your water heater regularly, especially around the bottom of the unit, can help you catch issues early before they become costly.

6. Outdoor Irrigation System Leaks

Lawn sprinklers and irrigation systems can spring leaks underground or in hard-to-see areas. Since these systems often run on timers or at night, problems may go undetected for months. Cracks in sprinkler lines, misaligned heads, or continuously soggy patches in your lawn could all indicate a leak. Seasonal checks can help ensure your landscaping isn’t costing you extra.

How Plumbing Leaks Increase Your Utility Bills

It doesn’t take a major pipe burst to see your water bill climb. Small, constant leaks add up quickly. A single leaking tap can waste thousands of litres of water every year, and multiple small issues across your home only magnify the waste.

Beyond the financial cost, unchecked leaks strain municipal water systems and contribute to unnecessary resource use. Leaks left unresolved for months can also lead to structural water damage and additional repair costs far beyond the water bill itself.

Why You Shouldn’t Ignore Hidden Leaks

Hidden leaks can slowly weaken your home from the inside out. If they’re left unchecked, you could face:

• Water damage inside walls or under floors, which often leads to expensive structural repairs
• Mould and mildew buildup in hidden areas, making air quality worse and cleanup more complicated
• Rising monthly bills from continuous water loss that adds up fast
• Emergency repair scenarios where a small leak turns into a burst pipe or a damaged foundation

Catching these leaks early means fewer surprises and lower repair costs. It also keeps your home safer and your plumbing system in better shape for the long haul.

Solve the Mystery of Your High Water Bill with Professional Plumbing Repair

If your water bill doesn’t match your usage, there’s likely a hidden issue behind the scenes. At Brothers Plumbing, we help Toronto homeowners uncover and fix the plumbing leaks that lead to surprise costs and prevent bigger problems down the line.

From leaky fixtures to more complex pipe repairs, our team is equipped to handle everything from routine fixes to emergency calls. We’ve been serving the GTA for over 50 years with fast, honest service and long-term solutions you can trust.

Give us a call at 416-656-6717, email us at info@brothersplumbing.ca or click here to get in touch online. Let’s take the guesswork out of your water bill and get your plumbing back on track.

FAQ: Sneaky Plumbing Leaks & High Water Bills

How do I know if I have a hidden leak?
Start by checking for signs like water stains, peeling paint, musty smells, or areas that are persistently damp. If your water bill is rising without explanation, it’s a good idea to call in a plumber.

Can small leaks really raise my water bill?
Absolutely. A slow drip can waste thousands of litres annually. Multiple small leaks can dramatically affect your usage—and your bill.

Should I try to fix a hidden leak myself?
Unless it’s a visible and minor issue, hidden leaks often require specialized tools and expertise. Improper DIY fixes can cause more damage.

What’s the most common hidden leak?
Toilet flapper leaks are especially common. They’re easy to miss and often cause toilets to run continuously, wasting water around the clock.

How often should I check for plumbing leaks?
We recommend a quick visual inspection every few months and keeping an eye on your water bill for any spikes that don’t match your usage.