Closeup on the top of a toilet sink.

Courtesy of Ebay

A bathroom has two vital components—a sink and a toilet. In the US, these items are typically separate and have their own areas in the bathroom. 

In other parts of the world, particularly places with limited space, they’ve found a way to combine the two most essential elements of a bathroom into one unit.

This article will explain what a toilet sink is, how it works, the benefits of owning one, and where you can purchase it. Read on to find out more about this innovative product.

What is a Sink Built Into The Toilet?

A sink built into the toilet, or a toilet sink, is an innovative way to save water, money, and space while caring for the environment and promoting sanitation. You can easily convert preexisting toilets into a toilet sink combo or purchase the complete unit at most home improvement stores.

How a Toilet With a Built-In Sink Works

Combining a toilet and a sink may sound complicated, but it’s a straightforward and user-friendly design. The toilet itself functions like a regular toilet; the difference is replacing the tank’s lid with a fitted sink and faucet. 

When you flush the toilet, clean water automatically flows through the sink’s faucet, and the water that drains after you wash your hands, known as greywater, is used to fill up the tank. The water from the tap automatically stops flowing when the float ball in the tank signifies that it’s full. 

Unsure about what greywater is? Well, let’s investigate!

What Is Greywater?

Greywater is reusable water from your bathroom or kitchen that homeowners can use to irrigate their lawn. Bear in mind that greywater is not drinkable and is often reused from showers and bathtubs. It typically goes through a screening process that removes waste products and can then be reused. 

A pipe from a greywater system that recycles water from an air conditioner dripping water into a bowl outside a home

A toilet sink is a perfect example of how to reuse greywater effectively. The soapy water that refills the tank after each hand washing not only helps to conserve and reuse water but also helps to keep the tank and toilet bowl clean and fresh-smelling. 

Benefits of Owning a Toilet Sink

There are a few notable benefits of owning a toilet sink. This product is for you if you want to save water, money, and space and keep things sanitary. 

Let’s break down each of these advantages in further detail.

Saving Water and Money One Flush at a Time

Owning a toilet sink is a simple, affordable way to move closer to a sustainable home, which benefits the environment and your wallet. The toilet sink’s efficiency and ability to reuse greywater allow for less wasted clean water, which means more money in your pocket. 

A typical toilet will use 1.6 gallons (6.05 liters) of water with every flush. However, some older toilets can use more than five gallons (18.9 liters) per flush, not to mention the approximately one-to-two gallons (3.7–7.57 liters) of water used to wash hands for about 20 seconds. 

Even more water is wasted if your equipment is older, inefficient, or if your faucet is leaking. Every droplet adds up in some way, and how it’s used and reused will be reflected in your monthly water bill. 

Creating Usable Space

A toilet sink is also a good option for people who want to maximize their bathroom floor space. Having a separate toilet and sink can occupy valuable bathroom space, which could be a struggle for those that already feel constrained by square footage in their home. 

a white toilet sink on the right with its benefits listed on the left
Courtesy of SinkTwice

The space saved with a toilet sink could easily be used for extra storage or provide room for an open bathroom concept. A toilet sink allows you to focus on your bathroom needs, leaving space for additional essentials.

Sanitation Matters

As a result of the toilet sink’s faucet automatically turning on when flushed, the need to touch a handle or knob is eliminated, which promotes cleanliness and helps keep the area sanitary. Having the sink and toilet in one isolated place also reduces the likelihood of germs spreading on the walk from the toilet to the sink.

Where To Buy a Toilet Sink

You can purchase most toilet sinks and parts from Amazon or your local home improvement store—it’s up to you to decide if you want to modify an existing toilet and add a sink or if you’d like to buy a whole new system.

If you’d like to add a sink to a toilet you already have in your home, these products could be great options for you:

  • Sink Twice for Toilet Tanks is fitted for tanks up to 16.8” (42.67 cm) wide – this plastic-based sink includes a touchless faucet and ample space for a soap dispenser. 
  • Sink Twice Adaptable Version for Tanks is also an option if you’re unsure about the sink size you need to fit your toilet’s tank – this sink fits toilet tanks up to 20.3″ (51.56 cm) wide and includes a touchless faucet and water flow modifiers that allow you to customize the water pressure to your preference. 
Promo photo of the Sink Twice Adaptable Version for Tanks
Courtesy of Amazon

What You Need To Know Before Purchasing

Now that we’ve explained the details of a toilet sink, how it can benefit you, and where you can buy one, we want to discuss three things you need to consider before purchasing a product like this.

Materials Matter: Plastic or Ceramic?

One crucial factor to consider is the material as you begin to narrow down which type of toilet sink you’d like to purchase. 

Some sinks are made of plastic and some of ceramic. Both are functional and safe. However, it would be beneficial to consider how frequently you will use your sink. A plastic sink might exhibit wear and tear faster than a ceramic sink, so keep that in mind as you decide.

Additionally, while ceramic might be more expensive than plastic, it will typically look better in most bathrooms, depending on your home aesthetic.

Closeup on the tap and bowl of a ceramic bathroom sink

Accessibility Versus Convenience

Another critical factor to consider before purchasing a toilet sink is who will use it. 

If you have children in the home, will they be able to reach the sink easily without the risk of falling into the toilet? Do any of your guests or family members have disabilities or difficulty reaching things independently? 

If so, it’s essential to consider whether having a toilet sink in a shared bathroom is feasible. 

If your home allows for it, you could also arrange for a toilet sink to be placed in your personal bathroom while keeping the standard setup for a shared bathroom, allowing everyone access to the type of facilities that best suit their needs. 

Cold Water Only?

The last important factor to consider before purchasing a toilet sink is the water temperature you prefer to wash your hands. 

These toilets are usually only connected to the cold water plumbing system, which means you won’t be able to wash your hands with hot water. However, since only cold water will come through the faucet, it’s worth considering whether or not you can live without washing your hands in warm water. 

If you have a second sink in your bathroom, this shouldn’t be a big problem. However, if your toilet sink is the only one available, you might want to reconsider whether it’s your best choice. 

Where do You Buy a Toilet Sink?

The good news is, since they aren’t that big, you can find them online. This will give you the best variety and lowest cost as well.

Home Depot and Sink Twice (can buy on Amazon below also) have some, and to my own surprise, Amazon actually had a good bit of them.

Here are the top 5 best selling toilet sinks on Amazon right now:

SaleBestseller No. 1
Sink Twice for toilet tanks measuring 15.25' - 16.8' (measured with lid off)
605 Reviews
Sink Twice for toilet tanks measuring 15.25" - 16.8" (measured with lid off)
  • Compatible with Tanks measuring 14" - 16.8" as measured with the lid off and with larger tanks with the Sink Twice Expansion kit (sold separately)
  • Touchless Automated Handwashing
  • Excellent Water, Space and Money Saver
  • Large Soap Dish Is Perfect for Dispensers
  • "Plasti-Tak" Mounting Putty can be helpful in affixing to some toilets (sold by a separate seller separately)
Bestseller No. 2
Essbhach Bathroom Vessel Sink, Wall Hung Basin Corner Sink Small Bathroom Sink, Left Hand White, Sink Only
  • 【Sink Dimension】The external dimensions: 14.49L" x 7.09"W x 3.54"H, Inner dimension: 9.96L" x 5.12"W x 2.2"H.
  • 【Easy to Clean】Durable and Smooth Ceramic small wall mounted sink is easy to clean from every angle, inside, outside and even underneath.
  • 【Installation Type】Wall mount, this rectangle vessel sink has two types—right hand and left hand. The package includes the wall mount sink sink and mounting hardware only. (Not include the faucet and pop-up drain)
  • 【Premium Quality Ceramic】This small sink is made from vitreous china, and white high gloss glaze finish. Which ideal for bathrooms, cloakrooms or utility rooms.
  • 【Warranty】As brand manufacture, its our great honor to give you enjoyable experience of this products. Please contact us on Amazon if you have any questions.
Bestseller No. 3
Sink Twice Adaptable version for tanks 15.3' - 20.3' measured with lid off
60 Reviews
Sink Twice Adaptable version for tanks 15.3" - 20.3" measured with lid off
  • Excellent Water, Space, And Money Saver
  • Touchless automated hand washing
  • Easy to install and adapts to function with most toilets with tanks 15.3" to 20.3" wide
  • Includes flow modifiers which can increase or decrease faucet flow as needed
  • This particular product assembly can adapt well to many different sized toilet tanks

Final Thoughts

A toilet sink is a simple, innovative product that has paved the way for implementing user-friendly, sustainable, everyday products that help make a difference with each use. Combining the two most important aspects of the bathroom – the toilet and sink – allows you to protect the environment and keep money in your pocket while conserving water and space.


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