Putting A Toilet Where A Sink Was: A Step-By-Step Guide

I recently took on the task of renovating my outdated bathroom. I lost a bet to one of my friends, and therefore I had to take it on as a DIY project. It was not going to be an easy task as I had never needed to do something like this on my own before. Plumbing was not my strong suit until I had to swap the toilet with the sink.

It is possible to put a toilet where a sink was. Experts in the field recommend that plumbing of any sort should only be done by qualified plumbers, as some tasks require permits.  The biggest challenge to this type of task is that the diameter of the drain pipes is entirely different.  

I decided to compile a step-by-step guide to help future do-it-yourself prospects not make mistakes when undertaking the task of renovating their bathrooms, but first, a few frequently asked questions.

Can You Put A Toilet Where A Sink Was?

Although there will be some changes you will need to make to the plumbing, you can do it. The feeding lines for the water on the sink might need extending, and it might be inside the wall, so you can imagine the work that will go into that. 

The drainage on toilets and sinks is also different in size. Because of drainage requirements, moving a toilet is more complicated than a sink since a toilet drain is much larger than a sink drain.

Another concern is what is underneath the toilet, and therefore what you might need to dig up to move the plumbing if your bathroom sits on a concrete slab.

Do Toilets And Sinks Use The Same Drains?

There is no real difference between where the sink or the toilet water goes to. When water is flushed down the drain, it goes into its device trap and the P trap.

Gravity is the force that pulls the water down the drainage system and adds enough speed to the water to help it get over the P trap as fast as possible, then into the drainage pipes. It prevents the effluent from getting trapped in the system and prevents clogging.

After this, the water keeps its momentum and flows down through the tubes and away to either the public sewage system or septic tanks. 

The drainage system connects to another pipe known as the lateral line or the lateral connection. It is the biggest drainage pipe in the house.

This connection is the lowest duct in the plumbing system and is covered up under the building and yard. Like the other vents in your home, the lateral line uses gravity. 

The lateral line is installed in a sloping position. It helps the water to gain momentum and propel the effluent forward and down the system.  It allows the wastewater to get through your garden and away from your house. 

What Should Be Considered Before Starting?

Consider the following points to execute a successful sink and toilet swap:

• The layout, design, and building codes– It is vitally important to plan a DIY task properly. In this case, some pipes could leak or drainage systems that clog up because of wrong slopes; worse than that, you could end up violating some building codes. 
• The tools, equipment, and materials required– It is incredibly frustrating to realize midway into a task that you are short on material or do not have the correct equipment or tools. It is also of importance to wear the correct personal protective equipment.
• Having the right skills for the task at hand– Do not attempt a task that you do not know anything about; you could get hurt or even flood your entire house.
• Final inspections after completing the task– Doing an inspection after the task is completed is essential because it ensures that everything is functioning correctly and is done correctly. Imagine finding out about a leak after putting all the drywall back, and everything is newly painted or tiled.

Putting A Toilet Where The Sink Was Step-By-Step

It is so much easier to get started now that the planning was appropriately executed. Here is a step-by-step guide on how to get this task done.

Step 1- Getting All Tools, Equipment, And Materials Ready

Tools I Used

• Hammer/sledgehammer-For the demolition
• Pry bar-For a bit of leverage
• Wrenches- For the plumbing
• Screwdrivers-For fixtures and flanges
• Circular saw-For cutting the floor
• Pipe cutters-For cutting pipes
• Drilling machine and drill bits-For various tasks
• Measuring tape-to make sure measurements are correct
• Spirit level or laser-to make sure that things are straight

Equipment I Used

• Safety goggles
• Gloves
• Overcoat
• Safety shoes

Materials I Used

• 3” drainpipe and fittings-a standard size for toilets
• 2” drainpipe and fittings-a standard size for sinks
• ½” flex pipe and fittings-a standard size for water supply to the toilet
• Toilet closet flange and spacer to connect the toilet to the drainpipe
• Wax ring for toilet-to seal the flange on the drainpipe
• Pipe caps-for closing off pipes no longer in use
• Pipe glue and primer-to seal and connect new pipes
• Various hardware- for fitment of systems, drywalling, and painting.
• Paint, rollers, and brushes-to repaint sections of the drywall or the tiles of your choice.

Step 2- Removing The Toilet, Sink And Preparing All Surfaces

It is essential at this step to make sure that you open up all spaces where the new plumbing must go. In cases where drain pipes are exposed, it is a good idea to tape them closed so that no debris or objects accidentally fall into your drainage system.

NOTE: Before removing any fixtures, water pipes, or drains, it is vital to shut off the water supply, switch off the water heating system, and ensure that all or most of the water has drained away. At times it may be necessary to blank off the waterlines with end stoppers (if you need to restore water supply for periods of time.) 

This part of the task might require some demolition to pieces of drywall or the floor but is all dependent on the design and layout of your bathroom.

After preparation and demolition, we will get to the next step in our task.

Step 3- Alterations To The Plumbing System

Ensure that measurements are done correctly; this will prevent a lot of unnecessary frustrations. Imagine that you finished all the plumbing, and then the cistern does not fit in between the wall and the shower. So by doing proper planning and measurement, you are all set for success.

It is time to relocate the drainage system for both the toilet and the sink. It is of utmost importance to make sure that the correct sizes of drainpipe go to the correct locations; you are going to require 3″ pipes and fittings for the toilet line and 2″ pipes and fittings for the sink; make sure that the connections between fittings like elbows and the pipes are glued adequately so that it seals the system, it is also important to note that the correct heights and distances need to be calculated. 

 Next, I relocated the water supply pipes to both of the new places. The toilet only needs a cold water supply, while the sink needs both cold and hot water supplies. During this step, I had to join the old water pipes to the new water lines that I installed to the sink and toilet locations.

TIP: Make sure that the new connections are situated in places where they can be concealed and be out of the way of the installation points of the sink and the toilet.

In my case, the new connections to the sink were inside the cabinet situated under my bathroom sink. I also ensured that the water supply connection to the toilet was as close to the cistern as possible to give everything a neat and professional appearance.

It just doesn’t look perfect when you have piping systems running along the face of a wall. I have to mention here that it was quite a time-consuming process, as I needed to remove two sections of the wall and a section of floor to get to all the points of alteration to the drainage system and the water supply lines.

The next step in this DIY task was to test the systems for leaks and functionality. I installed some old taps to the water supply pipes, which I removed again after the testing process.

The use of 90-degree elbows to the drainpipes was sufficient as I could pour water into the systems, this too was just a temporary solution just for the testing part of the systems, so I did not glue them in place.

It turned out that I was fortunate in this case as there were no leaks in the system, so now it was safe to remove the taps and the elbows that I used for the test. Remember to install the end stops again if you need to restore the water supply to your home.

It was now time to redo the walls and the floor, and I had to say that I was proud of my handy work at this stage of the process. After the painting and tiling and the last finishing touches to make everything neat, it felt like I was never going to be done.

So after getting some refreshments and getting over my self-pity, and waiting for everything to set and dry up, it was time to start with the last step.

Step 4- Installing The Toilet And Sink In Their New Places

The toilet installation was a breeze, not because I was competent, but thanks to a video I watched online. I was so happy that I planned all the connections out properly because everything just lined up perfectly.

I slid the toilet pedestal part into the drain, but only after I slid the toilet closet flange, spacer, and wax ring over the drainpipe, I secured the bottom of the toilet to the floor and then moved the sealing components of the toilet over onto the drainpipe to ensure a good seal.

Next, it was time to install the cistern part to the pedestal of the toilet; make sure that you read the installation instructions carefully.  Once again, the online videos I found on YouTube were extremely helpful.

After all the components were in place, connecting the flex pipe to the cistern was the next step in the process. I installed a new closed coupled system, so all the connections were neatly tucked behind the pedestal.

I also felt the need to install a tiny valve for maintenance purposes; it helps if you don’t have to shut down the water supply to the whole house. The toilet seat installation was next in line, it took me longer than anticipated, but I got it done.

The last step to the task was to install the cabinet and sink. Once again, I was very thankful that I took my time with measurements and planning as everything fit in so perfectly.

After leveling, I secured everything in place and installed the new mixing tap.

In Conclusion

The task of putting a toilet where a sink was, was a lot more complicated than I initially thought.

Still, after reflecting on the project’s outcome, I have to say that it is highly satisfying to me because it is hard to believe that it is the same bathroom that used to be so dreary and outdated.

It is possible to renovate a bathroom as a DIY project, but it is vital to research and follow the manufacturers’ guidelines. I also found it helpful to talk to experts and ask for advice.

I would not suggest anyone taking on a task like this without first looking at the considerations mentioned earlier in this post. I ended up saving money and learning a new skill, so from my perspective, it was a personal victory, and I will attempt it again in the future.