How to Seal Bathtub Overflow Drain

If you’ve ever had the unfortunate experience of a bathtub overflow, you know how important it is to fix the problem quickly. A burst pipe or blocked drain can lead to gallons of water spilling out onto your floors and furniture. This article will show you how to seal bathtub overflow drain so that it doesn’t happen again.

Bathtub overflow can be caused by several things, from a loose drain stopper to debris stuck in the pipes. Whatever the cause may be, you need to stop water from spilling out of your bathtub overflow drain as soon as possible. How you do it depends on the type of overflow drain valve and the style of tub you have.

How to Seal Bathtub Overflow Drain

Things You’ll Need

  • Caulk Gun
  • Putty Knife
  • Hand Scraper Tool
  • Razor scraper tool with a new blade
  • Plastic putty knife or stiff blade scraper
  • Cement backer board available at building supply stores.
  • 1-inch fiberglass mesh tape for tile grout

A Stepwise Guide on How to Seal Bathtub Overflow Drain

Step 1: Preparation

Turn off the main water supply and then drain the water system before continuing. Remove all fixtures you do not want to work on, such as bathtub spout and showerhead. Place a bucket below the pipe leading from overflow and remove this cover with either pliers or pipe wrench.

This is usually located near the valve or faucet leading into the tub or shower floor. Carefully lift pipe until threads are visible on the underside of the metal plate covering drain opening where the new tub will be placed, but do not entirely remove it yet as it may break if poorly handled.

Step 2: Remove the Cover Plate

Unscrew the cover from the top of the overflow drain and keep it safe to use later. Then, carefully lift the metal plate until you can see inside of tub overflow. If you cannot get a good view of the opening, use a flashlight for better illumination while checking for debris or existing plumbing materials that the former owner or builder might have left behind.

Step 3: Clear the Opening

For those who have no previous information on sealing bathtub overflow drains, you must clear away loose debris from the inside of the drain opening. Use a hand scraper by pulling any small particles stuck in the corner.

Another method would be to scrape off grease and hard deposits around the edge with a wire brush or stiff blade scraper by pulling outwardly towards the edges. This will help prevent mildew from growing within the corners of the enclosure.

Hand Scraper by Pulling  Any Particles

In case of stubborn dirt, use a razor scraper with a new blade to remove thick patches, though make sure this is done cautiously as certain types of these scrapers can easily damage metal if too much force is applied.

Step 4: Inspect the Assembly and Gasket

Once the drain opening is cleared, check for any signs of rusting or other forms of deterioration. If metal is worn down to the point that it becomes thin and brittle, you will need to replace this section.

However, if surfaces are still in good shape without too much wear, clean off small particles by scrubbing with water and apply a thin film of fiberglass adhesive using either a plastic putty knife (for smooth surfaces) or a hand scraper tool (for grooved areas).

Step 5: Removing the Gasket

Before installing a new gasket, you will need to remove the existing one. If there are no visible signs of deterioration around the opening, you can re-use it just as long as its edges are still tightly fit within the drain opening. To remove old gaskets, use a wire hanger or stiff blade scraper by pulling gently upward towards sidewalls without exerting much force not to damage them further.

Step 6: Installing a New Gasket

Once the old gasket has been removed, install a new one within the drain opening. Make sure it is fitted tightly around both sidewalls and the bottom of the opening so that no gaps are left between surfaces. Since this part is not load-bearing, it should be made from rubber or soft plastic for easier installation.

In the case of metal inserts, lubricate these with petroleum jelly before pressing into place within tub overflow assembly to avoid getting stuck inside the enclosure during subsequent steps. Now place the metal plate back on top of tub overflow. This is a crucial step in how to seal bathtub overflow drain.

Step 7: Preparing Cement Backer Board

Before sealing the bathtub overflow drain, you must create a cement wall using a backer board. This can be purchased at your local hardware store and comes in sheets that are three-quarters of an inch thick.

Create a Cement Wall  for Bathtub

Use a penknife or cutter within the toolbox to cut through the plane of these boards so they become easier to handle during subsequent steps. Next, fit one sheet onto the sidewall beneath the opening to extend up by eight inches from the bottom section. Make sure to leave a gap between this surface and the tub enclosure walls.

Step 8: Screeding Cement Backer Board

Once the sealant has been applied, you will need to level out the area where the cement backer board has been fitted into place using a screed trowel tool (for thinner materials) or margin trowel (for thicker ones).

Next, spread a layer of cement onto the area surrounding the opening and smooth the board into place using a straightedge. Sealing bathtub overflow drain is not tricky, but the correct screeding technique should be applied to avoid making mistakes by leveling out the surface too much or too little. Finally, allow the area to dry completely before continuing further.

Step 9: Applying Sealant at Tub Overflow Drain

Now put rubber gloves within the toolbox to protect hands from cement while applying sealant onto tub overflow drain.

Take out the caulking gun by pulling back the handle so that tube protrudes slightly beyond the cartridge slot. Bathtub overflow drain will need an adhesive compound known as silicone caulk which comes in natural or white form depending upon preference.

Place tip along sidewall directly beneath the opening, keeping it perfectly upright, so no excess is squeezed out during the process. Press the trigger on the gun slowly and hold the nozzle firmly over the bottom of the drain opening while squeezing the tube’s contents into place until the surface surrounding the gasket is covered with a generous layer of sealant.

Step 10: Replace the Plate

Once the sealant has dried, remove the backer board by pulling it up towards the sidewall while gently tapping the bottom edge against the tub surround. The bathtub overflow drain should have created a solid surface around the opening, which can now be put back into place using a screwdriver within the toolbox.

 Tighten Screws Use to Bathtub

Tighten screws to secure metal plate over drain aperture before replacing washer and O-ring gasket onto the underside of the fixture. Once in place, tighten screws with pliers until fasteners are firmly affixed and no longer slip out of opening or rotate without resistance during use. These steps will help in how to seal bathtub overflow drain.

Tips and Warnings


  • After the caulk has been set for 24 hours, you can test to see if your seal is working. Pour some water into the overflow drain and see if it’s still draining correctly.
  • To further protect your tub from water damage, you can invest in a rubber stopper for the overflow drain. Replace the old one if it is made of metal or has rusted.
  • A quick fix to an overflow that leaks during use is to place the showerhead into the filler neck until the leak stops. This will prevent your tub from leaking while taking a bath or showering.
  • If you can’t find the overflow cover on your tub, it’s probably hidden behind one of the jets. Remove the jet(s) to check for an overflow drain.


  • If you decide to remove the overflow drain, be sure to turn off your water supply before attempting any repairs or maintenance around your tub. Your main shutoff valve should be located somewhere near the floor in front of your tub.
  • Don’t attempt to clean under the overflow with harsh chemicals, as this can damage the finish on your tub and cause it to corrode more quickly than usual. Instead, use a spray cleaner and warm water only.
  • Keep children away from the tub when it’s filled with water, as they can drown in a full tub regardless of whether or not there is an overflow drain.
  • Keep your overflow cover and bathroom drains clean to prevent dirt and hair from clogging them.


Seal Bathtub Overflow Drain: A common problem with bathtubs is overflow. The water will eventually spill over the edge and onto the floor, which can create a mess in your bathroom or on your carpet if it’s below. Fortunately, there are ways to make sure this doesn’t happen again! We hope you have gone through the article on how to seal bathtub overflow drain, so you never have to worry about flooding your home again!

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