Disclaimer: BestOsmosisExperts is supported by readers. If you purchase something via links on this post, we may earn an affiliate commission at no extra cost to you.
Leaks are the most common plumbing issues faced by homeowners including toilet leaks. A toilet can last for many years with little maintenance. However, there are incidences when your toilet might leak at the base when flushed.
The leaking water will spill on the floor and cause serious water damage. That does not mean that your toilet has reached the end of its usage since such a leak can be easily fixed even without any plumbing experience.
What Causes a Toilet to Leak When Flushed?
The leaking water at the base of your toilet that occurs whenever you flush is normally caused by the failure of the seal located under your toilet. You will know that the wax seal has failed when water pools around the base of the toilet.
In some instances, the problem lies elsewhere meaning that you will have to know where the leaking problem is emanating from in your toilet. To pinpoint the issue soak up the water on the toilet’s floor with a sponge and use a towel to dry off the floor.
Wait for a new puddle of water to appear on your bathroom’s floor and check to ensure that water is actually coming from under the toilet. Other causes of the problem when the toilet is flushed include a faulty shutoff valve, a loose supply tube, sweating (condensation), or a cracked tank.
Other Causes of the Leak
Condensation: it occurs when water condenses outside the tank of the toilet and then drips on the toilet floor. It is commonly referred to as sweating and is usually caused by temperature difference inside and outside the tank. Specifically, the cold water inside the tank and the steamy and warm air outside the tank in the washroom.
The condensation takes place more often during the summer but can take place at any other time of the year provided the conditions for its occurrence are present.
The issue can be fixed by using tank liners to keep the cold water in the tank insulated from the warm air on the outside. Alternatively, you can use the anti-sweat tank valves that mix warm and cold water that comes inside the tank causing the temperature difference to be reduced outside and inside of the tank.
Leakage from between the toilet bowl and the tank:
The type of leakage can be detected using a colored water test. If the water comes from between the bowl and tank near the center, it could mean that a new tank-to-bowl sponge gasket is required, or new washers are needed for the bolts in the same area.
When water leaks from the tank to the bowl gasket, it will happen more frequently when the toilet is flushed. If water has gotten past the washers and bolts, it will usually appear to be closer to the toilet bowl’s sides far from the center and near the edge.
Repairing this problem will require you to detach the toilet tank from the toilet bowl and have the sponge gasket or washers replaced as necessary. The parts and the process needed to fix the leaking can vary based on the toilet model that you have in your home.
Leakage from inside the tank of the toilet:
Check if this is the case remove the lid of the tank carefully since the lid is usually fragile and slippery when it is wet. Add some coloring that is organic-based such as food color to the water in the toilet tank.
Wait for the water to settle and change color for 15 minutes. If you see any colored water from the tank you will know that the tank is leaking since the affected areas or areas will be highlighted. The tank will need to be replaced.
Fill valve (ballcock) shank gasket leak:
The valve allows water into the tank and is attached to the shank gasket inside the tank. The colored water test can determine the sort of leak. Look for cracks in the porcelain near and around the gasket.
If no damage is found the leakage problem can be fixed by tightening the shank nut located below the tank. Continue tightening the nut one quarter of a turn at a time, and observe to see if there are no more leaks. If there is still leakage after the fix then the gasket will have to be replaced.
For you to know if it is your gasket that is causing the leaking, you will have to disconnect the toilet tank from the rest of the toilet.
The complexity of removing then securing the tank will need you to work with a second person. Turn off the water supply and then flush until the tank empties.
Loosen the nuts which secure the hold-down bolts. Hold the bolt top with a screwdriver while loosening the nuts with a wrench.
Loosen the water supply line nut that secures the tank and pull the tank from the bowl. Inspect the rubber gasket for cracks or dry out. If either is the case then the solution is a replacement.
Leaking supply line:
The leaking water could be coming from nuts located on both ends of your toilet’s supply line where it attaches to the inlet of the toilet’s ballcock and the shut-off valve that is on the wall. If your supply line is rigid, try to replace the supply washer.
If the supply line is attached to the shut-off valve directly as a single-piece unit, use stainless steel water flexes that are flexible since they are reliable and easy to attach. Replace the single piece with a separate supply line that is flexible and a separate shut-off valve.
A flapper is the toilet part that lifts when the toilet is flushed. When the flapper is released from the valve seat water flows through the tank into the bowl to push waste away.
If the flapper is not sitting where it is supposed to sit, the toilet will not run smoothly since water will escape through the tank.
Fixing the issue will require you to turn off the water supply by the shut-off valve and remove the whole water from the tank by flushing the toilet. Put a bucket under the tank of the toilet to collect any water that escapes and mop any water spilled on the floor.
After this remove the lid of the toilet tank and inspect the flapper. If the rubber of the flapper is no longer pliable and soft, it is time to replace it.
To change it snap the old flapper to remove it from the chains leading to the flush handle. Then pop the new one into place and attach it to the chain of the flush handle. Turn the water on and fill the tank.
Leaking shut-off valve:
The shut-off valve has a pipe connection near the wall and water can seep from the pipe connection. If there is leaking the valve requires to be replaced.
In other instances tightening the valve onto the pipe may solve the problem based on the type of pipe or valve that is in your bathroom.
How to Fix a Toilet that Leaks when Flushed
Fixing a toilet that leaks at the base when flushed is not an uphill task. You can fix the leaking problem by tightening the closet bolts that usually secure the toilet to the floor. Remove the caps that enclose the bolts with a slotted screwdriver or a putty knife.
Tighten each bolt alternately using a wrench one at a time. Avoid applying too much pressure to prevent cracking the base of the toilet. If the tightening of the bolts does not stop the leakage, you will need to remove the toilet and replace the wax gasket.
Below is a step-by-step procedure of how a new gasket (wax ring) is supposed to be installed to create a seal that is watertight between the closet flange and the toilet. The procedure is simple and easy to undertake.
1. Removing the Toilet
The first step in the replacement of a wax gasket is turning the water supply off at the shut-off valve that can be found behind in the crawl space or basement directly beneath it just behind the toilet. Make sure the handle is turned clockwise all the way.
Flush the toilet after removing the tank’s lid. To drain the water from the tank, hold the handle. The water remaining in the tanks should be removed using a sponge and a small paper cup should be utilized to get rid the water remaining in the toilet bowl.
The first step is to disconnect the tube that supplies water by making the compression nut that is located on the shut-off valve loose. Attempt the disconnection with your hand before utilizing a wrench.
The second is to remove the caps from the closet bowl and then remove the nuts using a wrench. If the bolts spin as you turn the nut, use needlenose pliers to grasp the top. If the bolts are rusted or cannot come off, cut the nuts off using a mini-hacksaw carefully to avoid cutting the body of the toilet.
The third step is removing the toilet bowl. To break the wax seal, grab the rim of the toilet bowl and gently rock the toilet back and forth. Lift the bowl from the floor and put it on a cardboard piece, newspaper, or blanket.
Plug off the drainpipe with a towel or rag to prevent sewage gasses from escaping to the bathroom. Since wax rings cannot be recycled remove the old one and throw it away.
The fourth step is scrapping the old wax gasket off from the toilet’s bottom and the closet flange on the floor using a putty knife. Inspect the flange to ensure that it is not bent or cracked. If the flange is damaged replace it or use a repair strap to fill the missing piece.
The fifth step is installing the curved metal strap. The installation begins by loosening the screws that hold flange in place to the toilet floor. Followed by inserting a new closet bolt into the strap’s slot.
Tighten the screws of the flange to lock in place the strap. Install the remainder of the bolts in the flange and if they do not stand upright, pack some wax around the base of each bolt.
If you want the wax ring to easily slide into the outlet of the toilet, leave it in the sun for a while or dip in warm water for a few minutes. If you had cut off your old bolts replace them with new ones.
Setting a new wax gasket on the closet flange is the sixth step. Ensure that the wax gasket is perfectly centered.
Replacing the Toilet
Toilets can be fitted with an old-fashioned chrome-plated copper water supply tube, which may impede water flow. In this case, you should upgrade your plumbing with a flexible stainless steel-enmeshed polymer one. The flexible tube is easier to install and is durable.
The seventh step in fixing the toilet is applying a light coating of pipe joint compound at the ends of the water supply tube. Then tighten the end that leads to the ballcock shank that protrudes from the toilet tank’s bottom.
The eighth step is setting the toilet back in place. Ensure that the rag or towel that was placed at the drain pipe is removed. Grip the bowl at the hinges of the seat, then lift the toilet to the flange. Using the closet bolts as guidelines, place the toilet on the wax gasket.
Make sure the washers are set over the bolts and nuts are snugly threaded on. Press down the nuts on the bowl’s rim so that the gasket can be compressed before tightening the bolts.
Alternatively, you can tighten each bolt until each feels snug, then press down the toilet bowl, and once again tighten the nuts. Avoid exerting too much pressure as it will crack the toilet. Ensure that the tank is parallel with the back of the wall.
The ninth step is cutting the closet bolt with a hacksaw and then snap bolt caps on the bolts.
The tenth and last step is tightening the end of the tube that supplies water to the shut-off valve that is loose. Ensure that the valve is open and flush the toilet a couple of times if there is any leakage press the bowl down and ensure that the nuts are tightened some more.
If there is no leakage utilize the bathroom for a few weeks and then retighten the nuts after prying off the bolt caps. The toilet usually settles after a couple of uses.
Toilet leaks are quite common and when you experience them in your bathroom when flushing, there is no need to panic. While there are tons of reasons why the toilet may leak when flushed, all of them have a solution that can be an easy fix while some will require the replacement of the damaged part with a new one. Ensure that you are able to pinpoint the exact cause of the leaking before embarking on replacing a part or fixing it.