Installing a Kohler Highline Toilet
Updated: Sep 20
The Kohler Highline toilets are a series of so-called "comfort-height" toilets in which the user sits at the same height as in a standard chair. Like similar comfort-height toilets from other manufacturers, Highline toilets offer greater ease and convenience for users and are intended to be quick and easy to install. They are among many people, readily available off the shelves at big-box retailers such as Home Depot.
However, perhaps due to its low price and mass-market reach, the Kohler Highline product line has a few anomalies that make installation slightly more troublesome than it needs to be.
Kohler Highline toilet
Extra-thick wax ring
Toilet flange extender ring (if necessary)
Socket wrench and sockets
Oscillating tool or mini-hacksaw
A flexible water supply tube (if needed)
Remove the Old Toilet and Install the Wax Ring on the New Toilet
First, turn off the water supply to your existing toilet (or the main water shutoff valve to the entire house). Then, put on a pair of gloves and remove your existing toilet before continuing to the next step.
Most toilets are installed with a wax ring that fits over the bottom drain opening (the horn) to create a seal between the bottom of the toilet and the drain pipe. This system has been in place for many, many decades, and although there are now waxless silicone seals available (Sani-Seal is one brand name), a wax ring is still the default method and one that works very well.
However, one improvement you can make is to discard the budget wax ring provided by Kohler and instead buy an extra-thick wax ring, such as one from Fluidmaster or Lasco for about $8. This beefier ring will ensure a tight seal, provided you have the right distance between the toilet and floor. If the gap is too wide, use a flange extender ring to adjust the gap at the bottom of the toilet.
To apply the wax ring, first, turn the toilet upside down on a soft surface to prevent chipping or scratching of the porcelain. With the wax ring softened to room temperature, peel off the wrapping and stick it to the base opening of the toilet, with the rubber gasket portion pointing upward (it will be pointing downward into the toilet drain when you install the toilet).
Position the Toilet on the Drain Flange
Flip the toilet again, so it is now upright, with the bowl facing upward, and carefully set it onto the floor over the toilet drain flange, so the T-bolts on the flange feed up through the mounting holes on the base of the toilet. If applied while soft, the wax ring should remain stuck to the toilet as you turn it right-side-up. Take care as you do this so the soft wax does not brush walls or floors; the wax can be hard to clean off.
It helps to have an assistant for this action.
Compress the Wax Ring
Once the T-bolts are extending through the mounting holes on the base of the toilet, apply weight to the toilet bowl to press it down and compress the wax ring. (Wax rings are superior to silicone rings in this regard; they are easier to compress to whatever degree is needed.)
Be patient and use your entire weight to press the toilet down, until the toilet base is fully touching the bathroom floor.
Use a tape measure to double-check the measurements between the toilet bowl and the back wall. A good reference is to measure from the tank bolt openings to the back wall on each side. This will ensure that the toilet base is far enough from the wall to accept the toilet tank, and will also ensure the toilet base is square to the wall.
Secure the T-Bolts at the Base of the Toilet
Add the included plastic washer, metal washer, and nut (in that order) onto the two protruding brass T-bolts sticking up from the floor through the mounting holes on the base of the toilet.
Kohler's instructions merely state that you should not overtighten the nuts, but this should be emphasized: it is fairly easy to crack the Highline's base if you overtighten these mounting bolts. You can avoid this by using channel lock pliers to tighten these bolts, rather than a socket wrench.
Prepare the Tank
A peculiarity of the Kohler Highline toilet is that the gasket bolts on the bottom of the tank need to be forced back into the tank for the tank to fit properly onto the toilet bowl. If you do not do this, the tank bolts will not be long enough to extend down through the mounting holes on the toilet bowl.
Once the gaskets surrounding the bolts are forced back flush into the holes on the bottom of the tank, carefully position the tank onto the toilet bowl so the four tank bolts extend through the mounting holes.
Tighten the Tank Bolts
Thread the mounting nuts onto the tank bolts and hand-tighten them with your fingers. Then, tighten them down slightly more with a socket wrench and a 13 mm socket. The nuts should compress down into the rubber gaskets.
Take care not to overtighten these nuts. It is relatively easy to crack the bottom of the tank if you overtighten the nuts, or tighten them unevenly. Work back and forth between the four nuts to keep the pressure evenly distributed.
Level the Toilet Tank
As you are turning the tank's bolts, keep a bubble level on the top of the tank to check for level, both side-to-side and front-to-back. You can level the tank by selectively tightening or loosening the nuts securing the tank bolts.
Cut Off the Mounting Bolts
Some toilets come with two sets of floor mounting bolts, allowing you to choose the set that best matches your toilet flange. However, the Kohler Highline comes with just one set of fairly long bolts, so it is likely you will need to cut off the tops of the mounting bolts to allow the caps to fit over them.
Cut off the floor mounting bolts at about the half-way point. You can do this with a mini-hacksaw, but it is quicker using an oscillating tool (multi-tool) with a metal-cutting blade. If the vibration of the tool loosens the nuts, hold them with pliers as you cut off the bolts.
When the bolts are cut off at the right height, cover them with the provided caps.
Connect the Water Supply and Attach the Toilet Seat
If you are installing a new flexible water supply tube, connect it now. If you are reusing the existing water supply tube, connect it to the tailpiece on the water supply valve that extends down through the bottom of the toilet tank.
Normally, it is sufficient to hand-tighten the mounting nut onto the valve tailpiece, but if necessary you can tighten it a bit further with channel-lock pliers.
Place a shallow pan or tray beneath the valve tailpiece and slowly turn on the shutoff valve and watch for leaks. The toilet tank will fill with water and the toilet will be ready for use once it is full. If you see any leaks, slightly tighten the connections until the leak stops.
Finally, install the toilet seat, as directed by the manufacturer. Kohler toilets do not come with a toilet seat, so you'll need to purchase this separately.
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