Bath Tub Overflow What Every Homeowner Should Know

If your home has a bathtub then it has a gasket that seals the drainpipe connection to the tub. It’s very important that homeowners keep an eye on this connection point, because it’s highly prone to leaking.

Bathtub Overflow - What are we talking about?

Bathtubs are simple vessels that hold water, they are usually molded and set in to place and then connected to the homes’ plumbing. The bathtub fixtures are connected to supply lines that run through the walls and the drain and overflow are connected to the homes drain waste pipe system.

In the following diagram depicts the basic parts of this assembly, which includes, 1) The drainpipe, 2) the Gasket, 3) The Overflow Plate and screws. The overflow plate has slots on the bottom, that allow water to enter the drain pipe. This prevents the water in the tub from rising above this point and spilling out all over the bathroom floor.

Diagram of a Tub Overflow Gasket

The Overflow Gasket

The overflow gasket is itself, simple. Many older tubs had a felt gasket installed instead of a rubber gasket. These tend to have a shorter lifespan and can easily dry rot, leading to leakage around the gasket. Changing these out is generally straightforward and can be done without needing access to the plumbing within the wall. Although, having complete access to the plumbing does make the job easier.  There are numerous videos on YouTube demonstrating how to replace the gasket. If in doubt a plumber can easily replace the gasket.

In this YouTube video, the Lead Inspector for Tech Inspect Home Services shows a comparison of a dry-rotted felt gasket and a new gasket during routine home maintenance.

Why Is Replacing the Gasket Important?

When these gaskets leak, they allow water to enter the home’s interior structure. Keep in mind that the drainpipes are running vertically through a wall cavity behind the tub and then follow the drain horizontally throughout the home with a downward slope until it exits the house. If this gasket leaks and water can travel along the pipe, it can reach other parts of the home, and damage building materials not in direct contact with the tub.

Scenario 1: Imagine that the tub is located on a second story above the kitchen, and over time with the gasket leaking and kids taking baths and splashing lots of water, that water routinely enters the home’s structure, travels along the pipe and eventually dripping down onto the backside of the drywall installed on the ceiling of the kitchen.

Unfortunately, for the homeowner, you are not likely to catch this leak, until 1) a home inspector finds with a thermal imaging camera or 2) a water stain appears on the ceiling or 3) The Drywall collapses.

Scenario 2:  The tub is located on the main floor of the home, but the plumbing runs through the drop ceiling of a finished basement, and the drop ceiling has acoustic tiles. Drop ceiling tiles are highly absorbent and not likely to show signs of moisture damage, until either water stains show up or the tile collapses for the weight of the water being absorbed. If seen these crumble and fall apart firsthand after absorbing water from leaking pipes.

In both of these scenarios, water drips into the interior of the home causing damage to building materials, that could result in expensive and extensive repairs. Also, since these spaces are generally closed off, they do not receive much airflow and are slow to dry out. This creates a prime scenario for mold to begin growing, thriving and spreading within your home. Mold can begin growing in less than 24 hours, it requires moisture, food and time. If it water is present and does not dry out quickly enough or is continually resupplied, then mold can begin growing and may thrive.

Example picture of a tub’s drainage:

What Should Homeowners and Home Buyers Do?

The answer to this is simple, replace the gaskets regularly. Homeowners should change these gaskets out every 2 – 3 years to be help ensure that there’s no issues. It’s a $4 gasket that can literally save you thousands of dollars in damages and repairs.

For those buying a home, it’s important to understand that the home inspector is NOT required and will NOT test the overflow drain, because they are very prone to leaking. It is also not required for the inspector to test the overflow drain in the InterNACHI Standards of Practice.

From the InterNACHI SOP:

Section 3.6 Plumbing, Subsection IV. The inspector is not required to: test shower pans, tub and shower surrounds or enclosures for leakage or for functional overflow protection. 

At Tech Inspect Home Services our recommendation is simple; plan on having the overflow gasket replaced on all tubs, as part of your “move-in” maintenance plan.