Replacing the toilet does not necessarily entail calling a professional plumber. If you have everything you need, most people who are accustomed not to rely on anyone can do it themselves. Read the instructions below to learn how to remove your old toilet and install your new one correctly!
Steps
Method 1 of 4: Removing the Old Toilet

Step 1. Drain off all the water
Turn off the water at the water inlet valve. Flush the toilet to remove most of the water (press the drain as long as possible). Use a plunger to remove any remaining water from the bowl and wipe it off with a sponge. Then use a sponge to remove the remaining water in the cistern.

Step 2. Disconnect the hose
Use a wrench to disconnect the water supply hose. If desired and possible, you can replace it with a new one. If you decide to keep the old hose, only disconnect it where it connects to the toilet.

Step 3. Unscrew the bolts
Remove the caps from the bolts at the bottom of the toilet, and then unscrew the bolts themselves. After that, unscrew the bolts that screw the cistern to the seat.

Step 4. Remove the tank
Grasp the tank with both hands and lift it up. Rock it slightly from side to side to make it easier to remove, and remember to bend your knees as you lift the tank up. Move it away, but keep the place waterproof, as there may still be water in the tank.

Step 5. Remove the seat
You can now remove the seat from the toilet. Grab the toilet and rock it from side to side to break the silicone layer underneath and lift it off the bolts. If the bolts are completely corroded and the toilet won't budge, you may need to use a hacksaw to cut the bolts. Remove the toilet and set it aside.
Method 2 of 4: Preparing a new toilet

Step 1. Plug the drain
Take an old rag and plug the drain hole to prevent gas from entering your home and possibly losing your tools in the drain! Just remember to pull it out when you install your new toilet.

Step 2. Unscrew the old bolts
Unscrew the old bolts from the edge (you may have to pull them slightly to the side, like a nail on which a painting hangs). Dispose of old bolts properly.

Step 3. Scrape off the silicone layer
Scrape off whatever remains of the silicone layer. Take a spatula, rag or any other tool for this. When scrubbed, dry thoroughly.

Step 4. Inspect the edge
The edge is a plastic or metal ring that sits under a layer of silicone. Examine it. If it is damaged, you will have to replace it. If the old edge is a little cracked or damaged, you can buy an adapter (or super edge) instead.

Step 5. Replace bolts
Now that you are done with the edge, you can screw new bolts to it. They should be screwed into long grooves in the same way as when hanging a picture.

Step 6. Apply a new layer of silicone
Place the new toilet on its side on a towel or other soft surface. Then apply a new silicone layer to the drain hole, with the plastic or rubber side facing out. Press down firmly so that it sticks.

Step 7. Remove the rag
It is very important! Don't forget to remove the rag from the drain!
Method 3 of 4: Installing a new toilet

Step 1. Install the toilet
Lift the new toilet and position it so that the anchor bolts go through the holes at the bottom. This will be easier if you first remove the tank and install only the toilet itself.

Step 2. Attach it to the silicone
Slightly rock the toilet back and forth, then push hard with your hands or sit on it. This will glue the toilet bowl to the silicone layer.

Step 3. Screw on the nuts and washers
Install new nuts and washers at the bottom of the toilet. But do not tighten them right away! Place a level on the toilet seat and use the pieces of wood under the base to level the toilet. Then tighten the bolts on each side, twisting each side in turn to keep the toilet aligned. Do not tighten the bolts too tight. You don't want your new toilet to crack!
During all these actions, do not move the toilet too much, otherwise you may break the insulating layer on the toilet

Step 4. Place the caps over the bolts
Place new caps on the anchor bolts. If they are too large, you can trim them with a hacksaw.

Step 5. Insert the tank bolts and gasket
Next, take a new tank and place it on its side. Insert the bolts and handle to drain from the inside of the tank, and then place a gasket around the hole at the base of the tank.

Step 6. Install and attach the tank
Take the cistern and place it on the base of the toilet so that the bolts go through the corresponding holes. Then insert the drain handle and bolts and tighten them, twisting each side in turn, as you did with the base of the toilet. Be careful not to tighten them too tightly.
Method 4 of 4: Finishing Touches

Step 1. Install the toilet flush valve
You may need to install a drain valve (a mechanism inside the drain tank) if it was not previously installed. When buying it, pay attention to the packaging, there should be installation instructions. You can also consult with the seller about this.

Step 2. Install the seat and cover
If they were not pre-installed, you will need to screw them to the toilet with the appropriate bolts.

Step 3. Connect the hose
Connect a new or old water supply hose if it was still in good condition.

Step 4. Turn on the water supply
Try rinsing off the water a couple of times to check for leaks.

Step 5. Seal the base of the toilet
Choose a suitable filler and carefully coat the base of the toilet with it. Everything will be ready when it is dry! Enjoy your new toilet!