A Guide to Toilet Leaks

If you’re concerned about some water that you found on your bathroom floor,

please rest assured that there are a number of common possible causes for the problem. After you eliminate the most obvious cause (poor aim?), consider the following before presuming the problem is with the seal between your toilet and the sewer line. Usually, the issue is less costly than the potentially expensive possibility of wastewater coming up from beneath your toilet.

Where to Start

Condensation: Probably the most common cause for excess water on the floor of a bathroom is water condensing on the outside of the toilet’s tank and dripping onto the floor. This is commonly referred to as the tank “sweating.” Tank condensation/sweat is caused by the difference in temperature of the water inside the tank, which is usually very cold, and the temperature of the air outside the tank in the bathroom, which is often warm and steamy. Tank condensation sometimes occurs more often in the summer months rather than the cold winter months, but can occur any time of year if the conditions are right.

There are easy solutions to this type of problem, such as toilet tank liners (which insulate the cold water inside the tank from the humid outside). Unfortunately, it’s not convenient to confirm the water on your floor is completely an issue of tank condensation/sweat. Basically, you will need to wipe the outside of your tank thoroughly with a towel and then over time, try to visually detect whether or not water is gathering on the outside of the tank again.

Water leaking from inside the toilet tank: Once you’ve confirmed that the problem you’re experiencing is not due to tank condensation, then the next best place to begin would be to eliminate the possibility of you having water leaking from the tank itself. This is a fairly easy thing to check. Start by removing your toilet tank lid (be very careful, because tank lids are extremely fragile, can be heavy and are usually slippery when wet) and add some organic-based coloring (such as food coloring) to your toilet tank water.

After adding the coloring, do NOT flush the tank, but instead wait a little while for the tank water to change color and settle. If after about 10-15 minutes (without flushing the tank) you find the water on your floor to be the same color as the colored water inside your tank, or if you see any colored drips coming from anywhere on your tank, then you’ll know you have water escaping from the toilet’s tank since that IS the only place you have the colored water.

The next thing to do would be to identify where the water is coming from. Any cracks in the porcelain tank should be discolored and highlighted by the tinted water. The tinted water will usually help in finding any leaks around the bolts and rubber seals between your tank and bowl or from the foam gasket where the flush valve allows water to enter the bowl.

Other Possibilities

Leaking shut-off valve: Make sure water isn’t seeping from the pipe connection behind the shut-off valve, near the wall. If it is, the valve may need to be replaced (although it may be possible for you to tighten the valve onto the pipe, depending upon the type of valve and pipe you have).

Leaking supply line: Check for water dripping from the nuts on each end of the supply line, where the line attaches both to the inlet of the toilet’s fill valve (on one end of the flex) and the shut-off valve on the wall (at the other end of the flex). If you have a rigid supply line, you can try replacing the supply washers. Sometimes the supply line will be attached directly to your shut-off valve as a single piece unit. We recommend using flexible stainless steel water flexes as they are easier to attach and are very reliable. If you do have the single piece valve-with-supply-line, we recommend replacing it with a separate shut-off valve and a flexible supply line (two separate pieces).

Water coming from elsewhere in the bathroom: Very often, your toilet will be the lowest fixture in the bathroom causing water from the shower or the bathtub to pool at your toilet. This will make it appear as if the water is coming from the toilet when in fact the cause is much simpler and less expensive. You can try adding a throw rug, or two, to your floors to see if this eliminates the problem.

And Finally…

Leaking from underneath the toilet: The wastewater should only seep past a bad wax ring if the water is backing up from further down the line. Even when a wax seal is bad, the water that is being flushed through a free drain shouldn’t escape past the wax on the closet flange (beneath the toilet) and onto the floor as the water is droppings straight down, directly from the toilet and into the waste line. If the water on your floor is obviously wastewater (indicated by its coloring and noticeable smell), then your problem is likely more than just a bad wax ring. Although you may not be experiencing a recurring overflow problem with your toilet, the water is still most likely backing up and out through the first point of least resistance (from beneath your toilet). Along with resealing your toilet bowl (with a new wax ring and perhaps caulking around the base), we strongly recommend you investigate the possibility of a stoppage in your waste lines. In that case, simply replacing the wax ring would not solve your issue and you could then encounter increased drainage problems due to the existing stoppage in your lines. The new wax ring may then fail if the wastewater was continually backing up to it.

If you are ever in doubt, please contact us either by phone, email,

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Tags: BathroomguideMaintenancePlumbingToilet

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