How to Detect & Fix a Leaky Toilet

For a personal finance writer, nothing is quite as satisfying as crafting a personal finance lesson to a toilet analogy: “Sometimes the leaks that hurt the most are the tiny ones that go undetected.”. Oh yeah, that felt good. But seriously, a tiny, unnoticed toilet leak can be quite pricey and wasteful. And they are extremely common. So, it’s in your best interests to detect and fix a toilet leak ASAP.

Consider some of these statistics from the EPA on water leaks:

• Leaks account for, on average, 10,000 gallons of water wasted in the home every year, which is enough to fill a backyard swimming pool.
• Fixing easily corrected household water leaks can save homeowners about 10% on their water bills.
• The amount of water leaked from U.S. homes could exceed more than 1 trillion gallons per year.
• 10% of homes have leaks that waste 90 gallons or more per day.

And toilet leaks can be the most problematic because they can leak quite a bit (200 gallons per day or more) and are not easy to detect. In fact, you could have one right now, and not even know it <please take this moment to shudder in horror>!

So what I’m going to share with you today is detect a toilet leak and fix it. I recently went through this myself and will share my story and the immediate results I saw in my water bill, after the fix.

How to Detect a Toilet Leak

One tried and true method for detecting if you have ANY leak in the house is to simply check your water meter.

1. write down a precise meter reading
2. wait 4 hours, while not using any water source
3. go back and check if there has been any change on the water meter. If there’s a change – you probably have a leak.

However, even this method might not pick up on tiny toilet leaks. For this, listen for your toilet to make re-filling sounds in between flushes. This means that your tank water levels have gone down and your valve is re-filling the tank to compensate for lower levels. This should not happen in between flushes after the tank has already re-filled. If it does, it’s a telltale sign that you have a leak.

Your valve may not be the most responsive, however, so the best method to detect a toilet leak, is to:

1. remove the tank lid and take some food dye (beet juice, tomato juice, or other dark juice also works) and drop it in to the tank
2. wait and check back after 10-20 minutes
3. if the tank has changed water color, and you do not see any of that color in the bowl – you are likely leak free. If, however, the coloring you placed in the tank is now in the bowl (for example, see picture to the right), you have a leak.

Leaky Toilet Causes

To understand what causes a toilet to leak, it’s important to understand how a toilet works.

When you flush a toilet, water from the tank is released by a the lifting of a rubber flapper attached to the flush handle – into the toilet bowl. When I speak of a “leaky toilet”, what I am really referring to is a tank that is leaking in to the bowl without it being purposefully flushed.

This usually happens for one of three reasons:

1. the rubber flapper deteriorates or warps, creating small weak points penetrable by water
2. mineral or other material buildup on the flapper or flapper valve seal (what the flapper rests on to prevent water from leaking in to the bowl) – creating an imperfect seal that leaks
3. your tank water level is set too low. A sealed flapper/valve needs adequate weight from having enough water sitting on top of it

How to Fix a Leaky Toilet

The fix to a valve that has been adjusted so that water level is too low (#3 ) requires you to adjust the fill valve so that the water level in the tank is raised.

The most likely cause (#1 or #2) will require you to get deep and personal with your toilet flapper (one is pictured to the right, but they take on all kinds of sizes/colors). The best way to fix a leaky flapper is to clean off any buildup on the bottom of the flapper or top of the valve seal. DO NOT use a scrubbing device that would create any imperfections on the surface, as that will only make your problem worse.

If this does not fix the problem – it’s time to get a new flapper. Toilet flappers are cheap – usually in the $4-7 range.

To effectively replace your flapper:

• Check your toilet make and model (usually stamped on the inside of the tank).
• Take your old flapper with you to the store (make sure you shut off the water valve, or you’re going to waste a ton of water).
• Go to the hardware store and look at the flappers in stock. Try to match up the flappers by the style and size, as how they connect and pivot at the valve base is key to finding a good match. Knowing your toilet make/model will also help you in this process, as the flapper manufacturers will list compatibility on their packaging. Here’s the best selling toilet flapper on Amazon (costing around $6).

Getting a flapper that fixes the leak might take a bit of trial and error. I literally went through 6 different flappers before finding the perfect fitting one that stopped the toilet from leaking (a DoIt Best Hardware generic product).

If a toilet flapper doesn’t do the trick, you should pick up a new toilet fill valve kit (about $15), as you are likely to have an issue with your valve. These are fairly easily to install.

Sadly, I had gone months before realizing that a toilet leak was even an issue. First, my old float model valve sprung an unrepairable leak. After replacing it with a brand new valve, I noticed that my toilet would run in between flushing, to “top-off” the water in the tank. This wasn’t noticeable prior to replacing the valve, but now it was. And it was re-filling often. I double checked, using the food dye method highlighted above, and there was leak.

After fixing the toilet leak, I noticed my water bill take a year/year decline (leak was fixed towards the end of May and water use was up in preceding months year/year, but down in subsequent months year/year after the fix).

I can’t say with 100% certainty that the leaky toilet flapper replacement was the reason for the dramatic turnaround, but I don’t really have any other plausible theories.

Bottom line: even if you don’t suspect that your toilet is leaking – check it out. Cleaning or replacing a toilet flapper is a cheap and easy DIY fix that anyone can do, and another great example of how you can insource some home maintenance and save yourself money.

Leaky Toilet Discussion:

• Have you ever had a leaky toilet that required fixing? How did you fix it and how much did it cost?
• How much in suspected savings did the fix generate?
• What DIY plumbing or other projects have you taken on to save money?

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