Learning CenterTub Waste and Overflow Guide

Tub Waste and Overflow Guide

The bathtub drain and overflow are important. Finding the right drain stopper isn't as complicated as you may think.

Blue claw foot bathtub with overflow drain in brushed nickel finish.

The tub drain is one of those simple plumbing marvels that most people may not think about unless there’s a clog or it is time for a bathtub drain replacement. The drain is also known as the tub waste and it is an integral part of the tub waste and overflow system in any bathtub drain replacement or update. One of the most common questions people have when buying a new tub is “What drain goes with this tub?” so we put together this guide to help you find the right tub stoppers for your bath. 

What is a Standard Overflow and Tub Waste? 

The tub waste is the bath drain on the floor that empties the tub. The overflow is a hole placed higher up along the wall of the tub and plumbed to the tub waste pipes. It is designed to gradually lower the water level, without opening the tub waste drain, to give displaced water an escape channel before it can reach the tub’s edge. The overflow prevents an overfull tub from spilling water over the sides thanks to a secondary drain or overflow tube that is located higher up on the side of the tub wall.  

Illustration of a tub waste overflow pipe.

The tub waste and overflow pipes connect to the same plumbing lines to drain the water out of the tub and prevent damage to the bathroom floor and tub surround. The tub waste and overflow may both require a trim kit, depending on the type of drain stopper you choose. Other factors in choosing a drain stopper include the style of the bath and the finish type that best fits the trim.

How Does a Bathtub Overflow Work? 

Illustbathtub faucet and water filling tub, overflow drain is round

A tub overflow functions as a “last line of defense” between the bathroom floor and the unexpected flood of an overfilled tub. It is an extra drain location to help remove water safely into the water waste line rather than allow it to spill out onto the floor or tub surround to warp or cause mildew buildup.  

 As the tub water level is displaced, the water level rises and channels into the bathtub overflow rather than over the tub edge. Some overflow drains are fitted to an external pipe that can be hidden in the wall or tub surround. There are bathtubs with built in overflow channels within the body of the tub itself that send the bathwater to the tub waste pipe.

Does a Tub Need an Overflow? 

It’s important to note that overflows and tub waste drains do not prevent overfilled and messy tubs. It is always best to monitor an open faucet and watch the water line to keep it well below the overflow drain. If the water level rises over the overflow hole, it can syphon off small amounts of water at a time, but the water may still go over the tub edge depending on how fast the water is displaced.  

 Because of this, bathtub overflows are not required by all residential housing or uniform plumbing codes, though some local codes may require them. As a result, not all tubs are built equipped with an overflow. If the tub has an overflow, it is still necessary to ensure it is properly connected to an overflow pipe and the water waste line. If not, the open overflow will leak water behind the tub and could damage the wall or tub surround.

Find the Right Bathtub Drain Assembly

2 tub overflow drains, one in gold finish and one in chrome finish.

Not all bathtub assemblies and drain stoppers are the same. The right drain depends on the type of tub you have as well as other factors, including: 

  • The pipe assembly material 
  • The actuator type 
  • The drain location measurements 
  • The drain stopper type 

When choosing a drain, look first to find one in the finish and style that you prefer. Drains and overflow types are fairly standard, so start with the style that fits your bath and be sure to get the right measurements for the assembly parts. 

Assembly Materials 

The pipes that make up the tub waste and overflow can be fit on-site to match the layout of your tub and plumbing. The material you choose does play a role in how easy it is to cut to size, as well as the life of the plumbing lines, and the type of fittings that can be used to join the lines to the rest of the plumbing. Check the type of material the tub connections currently utilize, and if it’s a new installation, check local codes for the necessary material type.  

 You will find tub waste and overflow assembly materials that include: 

  • ABS, or Acrylonitrile, Butadiene, Styrene 
  • Brass 
  • PP, or Polypropylene 
  • PVC, or Polyvinyl Chloride 

  Plan to use the same material as the existing plumbing lines that the tub waste will connect to. Some connection methods are more effective than others. For instance, slip joint connections can be used across different material types, while solvent-glued fittings should only be used between matching materials, such as ABS to ABS.  

 Using the wrong solvent to connect different types of plastic-based pipes can result in leaks and faulty seals, as well as cause the plumbing to deteriorate. PVC requires a specific PVC glue and is not interchangeable with ABS glue.  

Cable Driven Drain Assemblies 

Cable driven bathtub drains. Cable runs between knob and drain.

Cable drains are controlled by a knob installed in the overflow hole at the top of the waste pipe. The pieces run along the outside of the overflow and drainpipe, which makes for easier installation and maintenance. Turning the knob moves the cable to trigger the lever installed under the tub drain elbow and triggers the stopper to lower or raise to control the water flow.  

 The cable drain doesn’t require installation within the drainpipes directly, making them reliable and easy to clean, so these assemblies are becoming more popular than trip-lever actuators.

Trip Lever and Plunger Assemblies 

Trip lever drains with plunger mechanism in drain.

The trip-lever actuator lever mounted over the overflow plate has an internal plunger that moves to seal off the drainpipe itself. The plunger is attached to rods, within the overflow pipe, and is large enough in circumference within the pipe to seal off the pipe that connects to the tub drain. When the trip lever is raised, the plunger is lowered to seal the pipe entirely and the tub water is blocked at the pipe. The tub drain is blocked by a grate to keep debris out of the pipes.  

 With the plunger assemblies, always size the pieces appropriately. The rods that support the plunger must be the right length, otherwise the rods won’t hold it in place to block the pipe. 

Trip Lever and Rod Assemblies 

Another type of trip-lever actuator installed in the overflow hole uses multiple rods to connect to the stopper set into the tub. The rods in these assemblies are specifically shaped and can’t be fit on-site, so make sure to have exact measurements of the pipes between the overflow and the drain stopper.  

With these assemblies, lowering the trip lever actuator lowers the rods within the overflow pipe, applying pressure to a spring that turns a rocker arm connected to the tub stopper, lowering the stopper to seal and close. Raising the trip lever then releases the rocker arm and the pop-up drain releases.  

Because of the multiple pieces involved and housed within the drain shoe, this type of assembly can be more complicated to clean. Hair and other debris get caught on the springs and moving parts that run through the drainpipe and overflow, which can lead to clogs. It’s a good idea to clean these types of assemblies frequently. 

Find the Measurements for Tub Waste and Overflow Fixtures 

Much of the customization and sizing of the tub drain assembly can be done at the time of installation. Generally, drain and overflow kits are found in standard sizes and ready to be adjusted on site. While PVC is a lighter material, it is durable and the preferred tub waste material for many installers and plumbers. PVC pipe and other plumbing lines are easily cut to fit as needed, so check ahead of time to ensure the correct materials will be supplied by the installer.  

 There are a few simple measurements to have ready prior to choosing the bathtub waste and overflow type or planning for an installation. These measurements provide you with the minimum required lengths for the waste drain and assembly parts. 

The Drain Shoe Measurement 

tub waste overflow, measuring tape, section of pipe highlighted.

The overflow and tub waste assembly look something like an L shape when completed, with a vertical length of pipe connected to the p-trap under the tub, called the drain shoe or drain elbow. The horizontal drain shoe is measured by the distance between the center of the tub drain and the connection point between the drain and the waste tee that connects to the overflow tube.  

 This measurement requires looking under the tub, which is fairly easy when replacing a waste assembly on a freestanding tub, but slightly more difficult with a built in or alcove tub. Most freestanding tubs will have the overflow attached to the outside of the tub and visible with the other exposed pipes, such as the decorative faucet trims of a clawfoot tub. 

 For bathrooms with hidden plumbing, look for the access panel in the alcove or nearby wall that allows you to reach the internal plumbing. This could be in the bathroom itself, or in another room that shares the wall, such as a closet.  

 Not all homes will have a dedicated, removable panel and getting to the bath plumbing may require cutting into the wall. Other homes may have access areas under the flooring, or a basement or crawlspace access point, which may require professional assistance for maintenance. 

The Tub Height 

tub height measurement illustration.

The tub height is the measurement from the top edge of the bath directly down to the bathroom floor or tub surround. The tub depth is nearly the same measurement, only it is taken from the inside edge and down to the floor of the tub. Some overflow kits may use this measurement for sizing, so it’s good to have at hand. 

The Tub Overflow Depth 

Illustration showing bathtub water level.

Also known as the tub’s water depth, the overflow height is the distance from the interior floor of the tub to the edge of the bathtub overflow. This should be a straight, vertical measurement, so do not measure the curve of the tub. This is particularly important when choosing a lever-operated drain.


The Drain Hole

Illustration of bathtub showing drain hole with red line.

The last measurement to know is the drain hole size. The standard tub drain plug size is 1 ½” diameter. The drain size may be subject to local plumbing codes. The tub drain connects to the p-trap, or drain elbow, and should be large enough and unobstructed to allow the water to flow freely when opened.  

 Look for connecting strainers to install into the drain hole. They have threads that allow them to turn into place and hold them anchored. The strainer body allows different drain stoppers to be connected to the drain, as well as provides a hidden strainer to catch any larger debris that shouldn’t get lodged in the plumbing pipes. Some bathtub drain stoppers will come with the strainer included. 

 Note that there is a difference between a tub drain and a shower drain. Shower drain sizes can come in a variety of shapes, from circles to rectangles that run the length of the shower. They are intended to accommodate a larger volume of water at once. More importantly, shower drains do not close off to hold water standing on the shower floor and should not have bath drain taps installed. 

Are All Tub Drains the Same? 

Just as with bathtubs themselves, you have your choice in the type of tub drain that best fits. For instance, some freestanding tubs have an exterior overflow option with an exposed and visible bathtub overflow assembly, and the aesthetic it creates may inform the style of the tub drain you want on the inside. Specialty tubs may have additional plumbing considerations, such as with a whirlpool or air tub. For more information on specialty tubs, we put together a guide to explain the different types of bathtubs.

Finally, the last concern when choosing a bathtub trim kit is the fixture’s finish. The different drain types are available in a variety of finishes, from warm bronzes and brass colors, to traditional silver, or more modern black finishes. As well as considering the look of the finish within the tub, keep in mind that some living finishes, such as brass, can require special cleaning care and attention.

Matte black overflow drain. Gold tub tub filler, white drain finish.

When it comes to selecting a bathtub drain finish, look for a finish that will coordinate with the other finishes in the bathroom. It should complement the colors and finishes already chosen, from the sink faucet and vanity hardware, to the tub faucet and shower system. This careful selection provides a cohesive, completed look to the bath and shower area.

Bathtub Drain Stopper Types 

The tub drain type influences more than just the look of the drain trim. Some tub waste taps are a simple toe-touch operation while others require the user to reach under the water to open the drain to allow the water to flow from the bath. Other bathtub drain stoppers are lever-operated and can be opened or closed from the actuator installed at the overflow height. The type of drain stopper you choose should be easy and convenient to use, so know your options to find the best fit for your household.

Flip-it drain

The flip-it drain stopper is easy to use and simple to install. The stopper base pushes into the drain and is held in place with built-in O-rings. To use it, just flip the toggle-lever on the top of the stopper to activate or release the seal down over the drain. 

Lift and Turn drain

Lift and turn drains in chrome, brushed nickel and oil rubbed bronze finish

The lift-and-turn drain stopper installs into a crossbar strainer in the drain. The stopper is attached to a setscrew in the crossbar, and the stopper then threads down on it in order to close the drain. Turn the stopper knob the opposite direction to open it again. Because of the threaded screw, the user has some ability to control the flow of the water down the drain by how far up or down they turn the stopper.

Pop-up drain

The pop-up drain is a multi-part installation, much like the pop-up drains found in the vanity sink. A pop-up drain is controlled via either a cable drain or connected rod system that runs up through the overflow pipe to an actuator installed in the bathtub overflow hole. Turning the actuator moves the rods hidden in the pipe, which pulls the pop-up drain stopper closed and seals the drain. Simply reverse the action in order to open it again.

Push and Pull drain 

The push-and-pull drain stopper is attached to an inset-drain strainer body with a setscrew to keep it anchored, so that the drain stopper then pushes easily into place. Look for a rubber stopper to help ensure the seal to stop the water. Then pull the knob to release the seal and open the drain.

Toe-touch drain

Also known as the toe tap drain, the body of the toe-touch drain stopper is screwed into place within the drain to keep it secure. The stopper is spring-loaded, so pressing down on one edge of the stopper will press it into place over a rubber seal to prevent leaks. Pushing the opposite edge of the sealed stopper will release it again to open the drain. Look for a toe tap drain that has the two sides clearly marked to make it easier to use.

Trip-lever drain

The trip-lever drain stopper is another lever-activated drain, like the pop-up drain. When the lever mounted over the overflow is up, the drain is closed. Unlike the pop-up drain, the trip-lever drain stopper is a strainer fit into the drain, so it is not visibly obvious that the drain is closed or open, aside from the direction of the lever.