How to Seal a Leaking Flange Joint on a Hot Water Tank

by parker
YouTube video

Hot water tanks can sometimes develop leaks from the flange joint, which can cause water damage and other issues. In this article, we will discuss how to fix a leaking flange joint on a hot water tank. By following a few simple steps, you can effectively seal the leak and prevent further damage.

Step 1: Prepare the Tank

Before you begin any repair work, it is important to prepare the tank properly. Turn off the cold feed and the power to the tank. If necessary, drain the tank to a level below the leaking joint. This can be done by using a hose pipe and running the water down to a suitable drain location.

Step 2: Access the Flange Joint

Once the tank is prepared, you will need to access the flange joint. In most cases, there will be a fitting on the joint that connects to the central heating system. If this fitting is in the way, you will need to remove it before attempting to fix the leak. Use a pair of thin grips to carefully undo the nut on the flange joint.

Step 3: Prepare the Joint

After the flange joint is accessible, you will need to prepare it for sealing. Use a suitable sealing material, such as hemp and boss white plumbing tape, to create a watertight seal. Pull out a strand of hemp and twist it together to form a tight seal. Apply boss white plumbing tape to the joint, making sure to cover the entire area.

Step 4: Seal the Joint

Once the joint is prepared, it is time to seal it. Place the hemp seal inside the joint and apply additional boss white plumbing tape to ensure a secure seal. Make sure to cover the joint completely and wipe off any excess tape. Tighten the nut on the flange joint, making sure it is secure. Check for any leakage and wipe off any excess sealant.

Step 5: Test the Repair

Once the joint is sealed, it is time to test the repair. Turn on the cold feed and the power to the tank, and check for any signs of leakage. If the repair is successful, the leak should be sealed and the tank should function properly. If the leak persists, you may need to repeat the sealing process or consult a professional for further assistance.


Fixing a leaking flange joint on a hot water tank is a relatively straightforward process that can be done with a few simple tools and materials. By following the steps outlined in this article, you can effectively seal the leak and prevent any further damage. Remember to turn off the power and the cold feed before starting any repair work, and always test the repair before considering it complete.

By properly sealing the flange joint, you can ensure that your hot water tank functions properly and prevent any potential water damage. If you have any doubts or concerns about the repair process, it is always best to consult a professional for assistance. With a little effort and the right materials, you can successfully fix a leaking flange joint on a hot water tank and enjoy a leak-free system.

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