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How to Install a Toilet

Pro Referral > Home Guides > Plumbing > How to Install a Toilet
How to Install a Toilet

It’s ironic that it isn’t the bathtub or even the shower that makes a room a bathroom--it is the toilet. Add a toilet to a room and it immediately becomes a bathroom.


In most cases, you are not updating a toilet simply to add a new fixture. Issues with toilets can commonly be addressed with tweaks or with replacement parts, and toilets only need replacing if: 1.) there has been some sort of catastrophic failure or 2.) you are updating the larger bathroom space.


Toilets come in a mind boggling array of options. The single most important decision you’ll make when replacing your toilet is will your new toilet be a one-piece or a two? Due to cost, the two-piece has historically been the most popular. Consequently, this article will focus on installing a two-piece toilet.

Tools Materials Skill Level Estimated Time
• Rag • Toilet Beginner 1 to 1 1/2 hours
• Adjustable wrench • Wax ring (or appropriate toilet gasket)
• Ratcheting wrench (with nut drivers) • Closet bolts
• Channel locks • Toilet seat
• Flat head screwdriver (long handle) • Plumber’s putty
• Hammer • Teflon (plumber’s) tape
• 1/2” Cold chisel • Flexible supply line
• Mini-Hacksaw • Toilet shims (occasionally)
• 2” Putty knife (stiff)

    1. Purchase Your Toilet

    Toilets are marvels of modern engineering. They are typically made from white vitreous china with stands that can be quite sculptural. Attached hardware (the flush handle, etc.) is available in a full array of finishes, designed to coordinate with any other fixture finish you might find in a bathroom. Some incorporate microbial glazing, which both helps inhibit the growth of germs and also promotes ease of cleaning.


    Codes have required tighter restrictions on water usage. Today's "low flow" or super low flush, high efficiency toilets clock in at 1.6 and 1.28 gallons per flush (GPF), respectively. Toilets are available with both "round" and "elongated" bowls--consider things like bathroom door swing when deciding which to purchase for a swap out.


    Toilets with a bowl height of 17 to 18 inches are considered "comfort height" and are meant to help meet guidelines dictated by the Americans with Disabilities Act (ADA). Other options include pressure-assisted or hands-free flushing as well as other luxuries, such as electronically-controlled toilet seats.


    Important! The most important option to be aware of is “rough-in” depth. The standard placement for toilets in new construction is a 12" rough-in. That is--the center of the closet flange (the toilet drain) will sit 12 inches from the nearest rear, finished wall. Most home centers stock for this option. In older homes you may find, however, a 10" or a 14" rough-in. These toilets are still available, but usually through special order. Before you purchase a new toilet, it is a good idea to check your needed rough-in depth. Rough-in depth may not be an exact dimension. Rather it is often approximate and incremental, meaning a toilet designed to fit a 12” rough-in will work if the actual measurement is say 12 ½”. It may not if the measurement is 11 ½”.


    2. Inspect the Rough-In Plumbing

    The Closet Flange

    Toilets are mounted to the plumbing system at the closet flange. This is the circular ring, a fitting that caps the soil pipe, i.e. the toilet drain. Made of PVC or cast iron, toilet flanges can last a long time. They can become an issue however when removing existing older toilets. As closet bolts corrode over time, they become a challenge to remove from a closet flange. If replacing an existing toilet, remove the old closet bolts with care (as not to the damage the toilet flange).


    Note: Remove residue left behind from an existing wax gasket with a stiff putty knife. The closet flange should be absolutely clean before you begin your installation.


    The toilet flange also becomes a concern when, in the context of a remodel, you are changing floor heights. While there are various spacers and extension kits available, it may be best to enlist the help of a qualified contractor or plumber for determining the best way to approach this change. Ideally, you’ll finish the toilet flange such that its bottom edge rests on the plane of the finished floor.


    Toilet Supply

    One other consideration in the prep phase is the toilet's water supply. You’ll either find or set up the water supply so that it enters at the floor or through the wall at the left-hand side of the toilet (as you are facing it). Your water supply should by code be fitted with a shut-off valve. If one is not present, consider adding a shut-off with an angle up and a 3/8" compression fitting. In many cases a flexible braided toilet supply line should do, but in some cases where this supply will be more visible, consider chrome-plated copper tubing. Compression fittings and sizing will remain the same--in most cases you'll be looking for a 3/8" inlet and 7/8" outlet (for the fill valve connection).


    Installing the Closet Bolts

    Keyholes appear on either side of the closet flange. Slide your closet bolts in and twist, such that they catch the flange. Once inserted, they should be aligned and equidistant from the back wall of your installation. They should point straight up.


    Note: Closet bolts are not usually packaged with the toilet, but are sometimes paired with the needed wax rings or gaskets.


    3. Install the Bowl & Prep the Tank

    It sometimes makes sense to assemble the pieces of a two-piece unit, that is attach the tank to the bowl and add the toilet seat, prior to setting the toilet. For the sake of this article, we'll instead set the bowl then attach the tank and toilet seat.


    Start by unpacking your toilet. Set aside cardboard as it makes a good (protective) surface on which to assemble parts of the toilet. Set your selected wax ring in the sunlight passing through a nearby window, but only for a few minutes. This will help soften up the wax gasket, providing a better overall seal when you go to set the toilet. Turn the bowl upside down so that it rests on your cardboard. Gently apply pressure as you place the wax ring over the "toilet's horn."


    Wax Rings

    Wax rings are often fitted with sleeves that are designed to extend downward and slip inside the closet flange. The wax rings themselves come in various thicknesses as indicated by numbers 1 to 10 (non-contiguously), with 10 being the thickest. Here again, a surprising array of options appear for toilet gaskets and wax rings, including newer waxless options. Select a thicker gasket if flooring near the toilet is irregular or out of level.


    Setting the Toilet Bowl

    Align the holes on the bowl's base with the closet bolts as they extend upward, and set the toilet. Push gently downward so that your gasket can create a positive seal. Attach the bowl to the closet bolts using the toilet's pre-packaged cap trim, washers, and nuts. Use an adjustable wrench or a ratcheting wrench and tighten a few turns at a time, alternating side by side until the toilet is snug to the floor.


    Important! Do not overtighten these nuts as toilet bowls can crack easily. Check the distance from the rear wall using a tape measure, and the top of the bowl with a level.


    Prep to Install the Tank

    Flip the tank over and place the "spud washer" over the flush valve’s neck such that it sits perfectly flush with the bottom of the tank. Using Teflon tape, give the lower threads of the fill valve’s tailpipe a couple of wraps clockwise. If motivated, install your flexible toilet supply line at this point with an adjustable wrench. Hand tighten the supply line and give it a quarter turn using channel locks (protect its jaws with electrical tape or similar to prevent marring).


    Most tanks come fully assembled, but if yours does not, follow manufacturer’s instructions for setting up the fill valve, flush handle, and valve plus the float. Insert the tank’s mounting bolts through supplied rubber washers. Set these aside, but keep them near.


    4. Install the Tank

    Set the tank onto the bowl. The tank's flush valve should align with the hole in the rear of the bowl (surprisingly referred to as an inlet). Swivel the tank so that the mounting holes in the bottom of the tank align with bowl's bolt holes. Insert the tank's mounting bolts, prepped above, through the holes of the tank, and pass them through the corresponding holes in the bowl's rear flange.


    Now working from the bottom of the toilet, place any additionally provided washers over the bolts and tighten them down with provided nuts. Similar to working with the bowl above, alternate from one bolt to the other until the tank is tightened down. Use a slotted screwdriver for the tank bolts and a ratcheting wrench for the nut. As you get closer to completely tightening the bolt, it may be necessary to hold the bolt in place from above with the slotted screwdriver while tightening from below with your socket wrench.


    Important! Do not overtighten! Check for squareness of the tank to the bowl and the rear wall. If in doubt, employ a tape measure.


    5. Final Connections & Install the Toilet Seat

    Connect the water supply line to the water supply’s shut-off. Because it is a compression fitting (and they can be overtightened), tighten by hand and then give it a 1/4 turn with an adjustable wrench. Turn on the shut-off valve and fill the toilet tank. Inspect for leaks, tightening connections as needed. Fill valves allow for adjustments in water level--make adjustments according to manufacturer instructions if needed.


    Install the Toilet Seat

    Methods and systems of installation for toilet seats will vary. It has become a minor trend that toilet seats are now included with toilets, but in many cases they are available independently. Make sure to purchase a seat that corresponds with your bowl shape (round or elongated).


    Attach the toilet seat by working from above and below simultaneously. Use an appropriate screwdriver and thread the toilet seat bolts through provided (often winged) nuts. Tighten to the point where the seat's flanges do not wiggle. Do not overtighten.


    Install the Bolt Caps

    Some closet bolts come pre-creased to allow for an easy snap off (if needed). Otherwise, and if necessary, work carefully and cut down closet bolts with a mini hacksaw. Line the inside of the toilet’s provided bolt caps with plumber’s putty and install the caps.


Level of Difficulty

The act of installing a toilet is an easy job. Any homeowner with DIY hopes should strive to undertake this project. A toilet installation becomes slightly more difficult when modifications to the toilet flange or the soil pipe are required. In the midst of a remodel, floor height may change, so research appropriate methods for handling this adjustment. Damaged, cracked, or broken toilet flanges are also common in cases where an existing toilet had been leaking or was removed.


Find a Pro

If installing a toilet in a location where a toilet was not previously present, it is best to consult with a licensed plumber before adding to the home's piping. Be sure to contact a licensed and insured Toilet Installation Pro to get your toilet installed in no time.

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