Last Updated: February 25, 2026 — Reviewed by Brian Hayes, Licensed Master Plumber
Is your toilet tank leaking water into your toilet bowl? There may be a few things causing this. Don’t worry though as there are also some easy ways you can check this problem.
See If Your Toilet Tank is Really Leaking
Before you do anything, you want to make sure that this is what’s really happening. There is a very simple way to do this. Just out a few drops of food coloring into the water tank. Do not use the toilet overnight, or at least a few hours. Check the bowl and see if there is any hint of the color you added in the tank. If so, your tank is definitely leaking. Another way is to see if your toilet runs water into the tank by itself, stops, and runs again.
Find Out the Cause
There may be a couple of things causing this leak. Once you have discovered the real culprit, you can then take the necessary steps to address it.
- The Toilet Flapper May Be Malfunctioning
The rubber flap at the bottom of the water holding tank may not be working as it should. This is probably the most common cause of water tank leaks. See, when the rubber flap is not working as it should, it’s not closing tightly enough, and water can refill the holding tank. Remove the lid and flush the toilet while you’re holding the flapper. Dry it off and apply petroleum jelly to the rubber that meets the tank opening. This could help fix the issue. If it doesn’t, a replacement might be necessary.
- The Assembly Might Be Loose
If the bolts that holds the toilet tank to the bowl are loose, that may also be behind the leak. If the nuts are loose, you can try tightening them using a wrench. Just be careful that you do not tighten them too much as excessive force could crack the porcelain tank.
- There May be Cracks in the Holding Tank
If the holding tank is cracked, that’s also a possible reason for the leak. If this is the culprit, the only thing you can do is call a professional to have your toilet replaced. If the crack goes on to split, that could flood your bathroom or worse, your home!
If the leaks from your toilet tank is causing you too much trouble, it’s best to have it checked by a professional plumber. Call Hayes Plumbing right away, and we’d have one of our expert plumbers solve the problem for you in no time!
Additional Resources
Frequently Asked Questions
How much does plumbing leak cost in Oshawa?
The cost of plumbing leak in Oshawa varies depending on the scope of work, materials selected, and bathroom size. Hayes Plumbing provides free in-home estimates throughout Durham Region so you know exactly what to expect before any work begins.
How long does plumbing leak take to complete?
Most plumbing leak projects in Durham Region take between 2 and 4 weeks depending on the complexity and material lead times. Hayes Plumbing coordinates all trades to keep your project on schedule.
Do I need a permit for plumbing leak in Ontario?
In Ontario, you typically need a building permit if your plumbing leak project involves structural changes or moving plumbing lines. Hayes Plumbing can advise whether your specific project requires a permit from the City of Oshawa.
Need help with your bathroom renovation? Hayes Plumbing & Bathroom Renovations serves Oshawa, Ajax, Whitby, Clarington, and Pickering. Contact us or call (905) 576-3043 for a free estimate.
