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toilet tank sink

Toilet Tank Sink: An in-Depth Guide

By Maria Saxton Rise Writer
Aug 21, 2017

A surprisingly old idea made new again, the toilet sink (or toilet-top sink) has increased in popularity among homeowners who are conscious of their water consumption. A toilet sink allows you to conserve water every time you flush the toilet. Sounds too good to be true, right? Let’s dive into this nifty device.

Table of Contents

  1. What Is a Toilet Tank Sink?
  2. How Does a Toilet Tank Sink Work?
  3. When Was the Toilet Tank Sink Invented?
  4. Is Toilet Tank Sink Water Clean?
  5. Where Can I Buy a Toilet Tank Sink?
  6. SinkPositive Toilet Tank Sink
  7. Roca Toilet Tank Sink
  8. STAND Toilet Tank Sink
toilet sink
Image courtesy of Dane George

What Is a Toilet Tank Sink?

Toilet tank sinks, commonly referred to as a toilet sink combo, are available as a new toilet or retrofit for an existing toilet. Sink Positive has developed an adjustable, retrofit sink-lid for existing toilets that you can install yourself without needing a plumber or a whole new toilet. Modern styles come to market that places the sink to the side, so there is no awkward leaning over the toilet bowl to wash your hands.

How Does a Toilet Tank Sink Work?

A toilet tank sink is a device that uses gravity to conserve water. When the sink is used for handwashing, gravity brings the water into the toilet tank for the next use. Each flush will save a few gallons of water, which adds up significantly over time.

The sink itself gets installed where the top of the toilet tank would typically be. When you wash your hands, the used soapy water flows through a small tube that hooks up to the toilet supply and then fills the cistern for the next flush. This process means that you are flushing with greywater with each toilet flush you have already used to wash your hands rather than drinking water.

Today, more than ever, water is a precious resource. The toilet sink allows you to make the most of the water you are already using. Older toilet models can use as much as five gallons with a single flush! By installing a toilet sink, you can significantly reduce your water use. Not to mention, the less water you use, the more money you will save on your home’s utility bill. Win-win!

When Was the Toilet Tank Sink Invented?

According to Leonard Koren’s book 283 Useful Ideas from Japan, the toilet sink was invented over 60 years ago. The idea has recently caught on in other parts of the world with the growing concerns for freshwater availability, water use, and challenges associated with small spaces.

The toilet sink speaks to homeowners concerned with water consumption and those interested in saving space. It is not surprising that the toilet sink was initially invented in Japan, one of the world’s most densely populated countries. A toilet sink can be a solution to the challenges of confined living, especially in urban areas.

Is Toilet Tank Sink Water Clean?

Water from a toilet sink is just as clean as water you would get from a traditional sink since it comes directly from the water supply line. A toilet sink promotes sanitation because they allow for touch-free hand washing. This means you don’t need to touch the faucet knob or handle to turn on the water, thus decreasing germ transmission. There are approximately 1,000 bacteria per cubic centimeter on a bathroom sink faucet, which you can avoid using a toilet sink. It can even be more accessible to children than many traditional sink designs, providing excellent visual cues and reminders for children to wash their hands.

And, depending on what kind of handsoap you use, the used soapy water can even keep your toilet bowl cleaner and smelling better! You can connect either a hot or cold water line to the sink, depending on your preference. In addition, the toilet’s flushing power or other functions will not be compromised.

The refill process is automated, just like with a standard toilet. The float ball in the toilet tank will stop the water flow once the water rises to a certain level, ensuring that you won’t need to shut off the fill valve manually.

Pro Tip: Close the lid of the toilet before you wash your hands. This avoids splashing water on the toilet seat, so you maintain your popularity rating in your household!

Where Can I Buy a Toilet Tank Sink?

Toilet sinks offer an innovative redesign of conventional flush toilets. There are multiple toilet sink models available as an entirely new toilet or a retrofit for an existing toilet.

SinkPositive Toilet Tank Sink
SinkPositive Toilet Tank Sink

SinkPositive Toilet Tank Sink

SinkPositive is one of the most popular models for retrofit projects. They have developed an adjustable sink-lid for existing toilets that you can install yourself without hiring a plumber or purchasing an entirely new toilet. Their models cost under $150. With a small tweak to the toilet tank's connections, you can redirect the refill tube to the sink faucet. There are multiple tutorials available online to show you how easy the installation process can be. SinkPositive models are compatible with most toilets-- except for some dual-flush models. Even more affordable sink toilet models such as Sinktwice’s model for $75 can be found at Home Depot, Lowe’s, and even online on Amazon.

Some models are more complicated than others. Some features to look for include faucet aerators to soften the water flow and reduce splashing. It may be beneficial to look for a built-in soap tray for bar soap or liquid soap containers so that you have a place to put soap. If you are retrofitting an existing toilet, make sure that the model you purchase can adjust to your toilet's size to ensure it fits properly.

Roca toilet tank sink
Toilet Tank Sink. Photo Credit: Roca

Roca Toilet Tank Sink

Newer innovative styles are coming to the market that places the sink to the toilet side so that there is no awkward leaning over the toilet bowl to wash your hands. The company Roca sells a sleek modern version that illustrates this concept. This gives the toilet and sink a separated look and feel, although their systems are still connected.

STAND toilet tank sink
Toilet Tank Sink. Photo Credit: STAND

STAND Toilet Tank Sink

Conventional flush toilets aren’t the only toilet models getting a makeover. Another new style for business owners who want to retrofit their bathroom designs is the urinal-sink combo. A company called STAND has created this ingenious device to encourage handwashing in men’s bathrooms.

If you are extra brave, you can even make your own toilet sink system. The actual construction of a toilet sink is rather simple, and you can make a one-of-a-kind creation. There are a handful of examples of DIY toilet sinks projects available online.

Disclaimer: This article does not constitute a product endorsement however Rise does reserve the right to recommend relevant products based on the articles content to provide a more comprehensive experience for the reader.Last Modified: 2022-06-28T00:51:29+0000
Maria Saxton

Article by:

Maria Saxton

Located in Roanoke, Virginia, Maria Saxton holds a Ph.D. in Environmental Design and Planning from Virginia Tech. She works as an Environmental Planner and Housing Researcher for a local firm specializing in Community Planning, Architecture, Landscape Architecture, and Historic Preservation. Her dissertation explored the environmental impacts of small-scale homes. She serves as a volunteer board member for the Tiny Home Industry Association.