How To Fix a Leaking Toilet Cistern

Toilets that leak cost a lot of money and continued leaking leads to a waste of water. These days, water is a precious need and seeing it wasted because of a leak is just too painful. Your toilet is comprised of many parts and when it starts leaking from the cistern (or the tank if you will), this is a serious issue that needs to be remedied right away.

But here’s the deal: you can only repair your toilet cistern if you know where the leak is occurring. Usually, a leak happens in the water supply fitting (the joint between the tank and the bowl) of the toilet. Another reason for leaks is that the water is escaping into the bowl even when you’re not flushing the toilet. However, if you have a porcelain tank that is leaking, unfortunately the only solution for that is to have the cistern replaced.

Then again, it’s always best to check which other parts of the toilet are leaking. Why is that? Maybe the solutions can be very simple and may just require changing a few parts (that are also inexpensive). And that’s what this article is all about: to help you figure out where the leak is and provide the solutions to fix it.

What You Will Be Needing

Before you do any work on your toilet, make sure you have everything you need. This is important because you don’t want to be going back and forth between the tool cabinet and the bathroom when you have a leak to fix. That said, here’s what you will need to fix a leaking cistern:

  • adjustable wrench
  • sponge, chamois cloth or towels
  • ball-cock assembly
  • tank-to-bowl gasket
  • bolt assemblies

Fixing a Leaking Toilet Cistern

If the leak is in the water supply line

1. Check the point where the supply line meets the tank. Test to see if there are drips (use your fingers to verify). Also, check the line itself to see if its dripping.

2. See if the jamb nut holding the supply line to the tank is loose. If so, tighten the nut using an adjustable wrench. Make sure to do so carefully. The material a nut and fitting is made of is usually and nylon and when you over tightening it may cause it to strip. If you have a porcelain tank, this might be prone to cracking due to the pressure of nuts that are just too tight. For best results, make sure the nuts are snug with only a quarter turn or so past hand tightening.

3. If tightening the jam but didn’t solve the problem, replace the ball-cock assembly. A ball-cock is a term which is used when describing the water supply valve and float arm inside the toilet tank.

4. Turn the supply of water off at the shutoff valve which is located beneath the tank and near the floor. Drain the tank of water by flushing the toilet. Make sure the tank is really dry by mopping off excess water with a towel, sponge or chamois cloth.

5. With an adjustable wrench, loosen the jamb nut then pull out the old ball-cock then replace it with the new nut. Tighten the new nut but make sure not to make it too tight.

6. Turn the water back on. Check to see if there are still leaks after the tank has filled.

If the leak is in the tank-to-bowl assembly

1. Inspect the bolts holding the tank to the toilet bowl. Check to see if the nuts that are holding it in place are loose. If so, tighten them.

2. After tightening the nuts, check the connection to see if the leak still continues. If that is the case, you have to replace the gasket that seals the connection between the tank and bowl. Over time, these gaskets will lose their elasticity and as such, they will crack if they harden to a certain degree.

3. Shut the water supply through the shutoff valve. This valve is located beneath the tank. Drain water from the tank by flushing the toilet. Make sure any remaining water is dried using a chamois cloth, a sponge or a towel.

4. Loosen the nuts holding the bolts. Use a screwdriver to hold the top of the bolt then with an adjustable wrench, loosen the nuts. Loosen the jamb but that is securing the water supply to the tank.

5. Remove the tank free from the bowl. Take out the old gasket (this is shaped like a doughnut) and replace it with a new one (make sure to buy the one for your toilet).

6. Replace the tank back on top of the bowl. Insert the bolts and washers and tighten the nuts but make sure not to overdo it. Doing so might cause the porcelain to crack under the strain of the nuts.

7. Turn the water back on and check if there is still leaks after the tank has filled.

If the leak is caused by a leaking flapper

1. Check if the flapper valve isn’t seated correctly. The flapper is the device located at the bottom of the tank and its function is to prevent water from flowing into the bowl until the toilet is flushed.

2. Using food coloring, squeeze a few drops into the bowl and wait for a couple of minutes. You can leave the bathroom if you wish as this might take a while. The purpose of this exercise is to see whether or not the food coloring seeps through the bowl. If so, then it’s the flapper that leaks.

3. Turn the water supply off through the shutoff valve which is beneath the tank. Flush the toilet to drain the tank then wipe off any residual fluid with chamois cloth, towels or a sponge.

4. Inspect the flapper. If it’s no longer soft and pliable, you have to replace it because it has hardened. Snap this off, remove the chain leading to the flush handle, then install the new flapper and re-attach the chain.

5. Turn the water back on and check for leaks when the tank has filled up.

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