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Home » Blog » How to Fix a Slow Water Leak From a Toilet Tank

How to Fix a Slow Water Leak From a Toilet Tank

leak detection

A leaky toilet can be a distressing problem, regardless of how small or big it is. Whether water trickles from the tank to the toilet bowl or spills all over your bathroom floor, it will require some basic to intermediate plumbing skills to fix the problem. That said, it is not something that is too difficult for a regular homeowner to handle. However, suppose you feel like it is beyond your DIY plumbing skills, in that case you should go for a professional service. Many professionals offer leak detection services in San Diego that will fix your problem and provide the peace of mind you deserve.

Research shows that toilets account for 27% of the water used in an average American household on a daily basis. Add a leaky toilet to that, and you can see the entire picture for yourself. A leaky toilet wastes a tremendous amount of water every minute until it is fixed. Unfortunately, many of those leaks usually go undetected for a long time, as some of them are not that easy to spot. Luckily, you will know how to fix your leaky toilet tank by the end of this article. Before that, let’s have a look at how a toilet works.

How a Toilet Works

Before you rush off to repair your leaking toilet tank, it is better to have a basic understanding of how your toilet works and the overall mechanism of the fixture. You can do it by yourself by simply following the steps given below.

  1. Open the tank lid and flush the toilet a couple of times to better understand the following.
  2. When you flush, the chain attached inside to the handle will lift the flapper covering the opening of the flush valve.
  3. This will allow the water to flow from the tank into the toilet bowl.
  4. Then, the water coming from the tank will push the waste water in the toilet bowl into the drain through the trap.
  5. Once all the water has flowed from the tank to the bowl, the tank will be refilled once again by passing water through the fill valve into the tank.
  6. Once the tank is full, the flow of water will be stopped by the mechanism attached to the ballcock.

How To Know If Your Toilet Tank Is Leaking?

Now that you know the basic mechanism behind the operation of a toilet, we can move on to the next step. Unlike the majority of plumbing leaks, a slow water leak from the toilet tank can be challenging to spot. That is because it doesn’t show any obvious signs at the early stages of the leak. Therefore, we will talk about some simple methods on how you can detect the leakage of toilet tanks.

1. Using Toilet Tablets

This is an easy as well as a cost-effective way of testing whether your toilet tank is leaking or not. Wait until your tank is fully filled and close the water supply to the toilet. Then, place a tablet in the tank and wait for about ten minutes. If the tablet color has emerged into the water in the bowl, you have a leaky tank.

2. Checking the Water Level in the Tank

Similar to the method mentioned above, close the water supply to the toilet and mark the water level inside the tank using a pencil or a sharpie. Wait for about 10 minutes and remove the lid to see the water level. If it has gone down from your marking, it is another sign of a leaking tank.

3. Using Water Leak Sensors

Once installed, this device will flash a green LED if the toilet is working properly. If it detects a leak, it will flash a red LED and make a beeping sound. These sensors are not expensive either. They cost about $20 a piece and will be much cheaper than having a leaky toilet that adds a few cents to your water bills every minute.

4. Hiring a Professional Leak Detection Expert

This method will obviously cost you more than the above-mentioned methods but will also offer you lasting results. When you hire a professional such as the EZ leak detection expert in San Diego, they will take care of more than just a leaking toilet tank. Since they are highly trained and licensed for the job, you can be certain that they will properly identify your problem and fix it right.

Final Step Before You Begin Repairs

Before you get into repairs, there’s a couple of things that you should keep in mind. While fixing your leaky toilet tank may seem pretty easy at the outset, things can quickly escalate into total mayhem if you mess up a thing or two in the process. Therefore, it is best that you keep the following in mind before you move on.

  • Plumbing work is regulated by local and state codes. Therefore be aware of whether any of those apply to your DIY job or not before you start.
  • Don’t over tighten any metal and plastic appliances, such as nuts and bolts, as they will break under a lot of pressure.
  • Be careful when turning connectors and fasteners to avoid breaking or damaging them.
  • Some tank lids can be really heavier than they look (especially porcelain ones). So, carefully lift it and place it somewhere safely.
  • When purchasing replacement parts, make sure to double-check that they fit to avoid time-consuming trips to the store.
  • If the below-given tips don’t help fix your problem or you have trouble following them as mentioned, contact a licensed plumbing expert in San Diego to do the job for you.

Identifying the Cause of Your Toilet Tank Leak

In order to fix your tank leak, it is vital that you identify the location and the cause of the leak. Given below are some of the reasons for a typical toilet tank leak.

  • A leak where water enters or exits the tank – This can result in a leak in the water supply to the toilet, in the joint between the tank and the bowl, or water trickling from the tank into the bowl.
  • Condensation causing the water to drip from the tank onto the bathroom floor (Not a technical fault but still needs fixing).
  • A cracked tank.

Both the first and second problem can be repaired by doing some plumbing work. If you happen to find the cause of your leak as the third problem, i.e. a cracked tank, you have no option but to replace it with a new one. We highly recommend that you reach out to a specialist at EZ for leak detection services in San Diego for this job. It is not something that you should test your DIY plumbing skills on.

Things You Will Need

Following is a list of tools and materials that you will need for a typical toilet tank repair job.

  • Adjustable wrench
  • Sponge
  • Ball-cock assembly
  • Tank-to-bowl gasket
  • Bolt assemblies

After all of this, if you feel like it is too much for you to handle, you can always turn to a licensed leak detection expert in San Diego and get the job done. They will provide a clear cause of the leak and an origin report specifying your problem.

Check The Water Supply Line

Check whether you can see any water dripping from the joint where the tank and the water supply line meet. If there is no visibility of dripping of water, test it with your fingers for drips.

Also, check whether the jamb nut of the water supply line is loose or not. If it is, slowly tighten it with an adjustable wrench. It is important that you do it with care because it can break or crack in case you overtighten it.

If the leak still didn’t stop, you can try replacing the fill valve assembly. Turn off the water supply to the tank using the shutoff valve fixed onto the wall. Then, empty the tank by flushing all the water. Loosen the jamb nut holding the ball cock assembly using a wrench. Then place the new ball cock in the same place and tighten back the new nut. Turn on the water back and see if it fixes the problem.

Inspect The Tank-to-Bowl Assembly

Check the nuts of the joint connecting the tank and the bowl. Inspect whether they are loose or not and tighten it if required.

If the problem still persists, you will have to replace the gasket that seals the connection between the tank and bowl. It is very common for these gaskets to lose elasticity over time and start leaking.

Turn off the water supply to the tank using the shutoff valve fixed onto the wall. Then, empty the tank by flushing all the water. Separate the tank from the entire toilet unit by removing the nuts and bolts that connect it to the whole fixture. Loosen the jamb nut of the joint that connects the water supply to the tank as well.

Remove the old gasket (the black color doughnut shape thing) and replace it with the new one. Place the tank back on top and tighten back the nuts and bolts that you removed.

A Leaking Flapper

Inspect whether the flapper valve seats properly. Flapper is the valve at the bottom of the tank, holding the tank’s water from flowing into the bowl. If it is not fixed properly, it allows small amounts of water to trickle into the bowl.

You can test this by using the toilet tablets mentioned earlier in this post. If you find that you have an ineffective flapper, you will have to replace it.

Turn off the water supply from the shutoff valve and flush the toilet to empty the tank. Remove the flapper and the chain attached to the flush handle. Place the new flapper properly and re-attach the chain.

Importance of Routine Leak Detection Tests

As it might have already occurred to you, slow water leaks from your toilet tank can be difficult to spot. It will often go unnoticed by the untrained eye of a regular homeowner. Therefore, it is wise to schedule routine leak detection tests with a plumbing expert at EZ leak detection in San Diego. When you reach out to a professional, you can enjoy your peace of mind by knowing that you are free from all such problems.


Finally, you know what you need to follow when you are undertaking a DIY toilet tank repair job. It is important that you keep in mind the factors you need to go through before rushing off to repairs. If you feel like it’s a job beyond what you can handle, it is also wise to reach out to a professional leak detection expert and let them take care of the job.

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