Ideally, it should be about 1/4 inch above a finished floor.
The flange should sit flush on top of the new tile floor with only the thickness of the flange itself above floor level. The flange needs to be bolted to the floor, and then the new toilet leveled on the new tile floor and bolted to the flange. The wax seal will work properly that way.
The flange should go on top of the finished floor, so if the top of the flange is 3/8'' above the finished floor, that's practically-ideal. If the bottom of the flange is 3/8'' above the finished floor, as Terry points out, when you dry-fit it the toilet, it still shouldn't be resting on the flange.
The plumbers advise the opposite. Put the seal on the toilet horn first, then set it in place. Wax rings though are places on the flange first. I concur with cacher_chick's suggestion on the extra nuts on the flange bolts.
What Is the Correct Height for a Toilet Flange? The correct height for a toilet flange is about 1/4 inch above the floor, which should be finished. Always install the floor before the toilet flange, making sure it is level to prevent leaks or a rocking base.
Ceiling or Floor Damage
Just because you can't see the water doesn't mean that it isn't doing a lot of damage. In fact, toilet leaks that get into the floor or ceiling cause serious damage that could end up with the toilet falling through the floor.
Reasons to Caulk Around a Toilet
Moisture Prevention: Without caulk around the toilet base, external water can seep under the toilet, leading to floor and subfloor damage over time. This is especially important in bathrooms with wooden floors, as prolonged exposure to moisture can lead to rot and structural issues.
The optimum flange height for a toilet is about one-quarter inch off of a finished floor. If your flange sits at this height, almost any type of wax ring can be used to deliver a solid seal. The flange height may be less than optimal if you have just installed a new floor.
Wax-free Toilet Seals: The New Kid on the Block
For plumbers interested in a mess-free option, wax-free toilet seals check this box. These seals affix to the toilet using a strong adhesive. There's no wrangling the ring in into place. It's a straightforward method of keeping your toilet base leak free.
Toilets usually rock because they are not resting flush against the floor. Underneath the toilet base is a round toilet flange that connects the toilet to the drain pipe. If the flange is a little higher than the surrounding flooring, the toilet becomes raised slightly in the center, allowing it to rock to either side.
See whether you can jiggle either of the bolts underneath with your fingers. If a bolt is loose, simply use a socket wrench to tighten the nut until you feel some resistance. (Beware of overtightening — you don't want to crack the porcelain of the toilet itself.)
A toilet flange that's too high can cause instability, as the toilet won't sit evenly on the floor. This can lead to an uneven seating experience, as well as increased wear on the wax ring.
It's an a Push Tite gasketed closet flange. Simply push this down into the old closet flange and secure it to the wood subfloor with galvanized or stainless steel screws.
These flanges install on the outside of either 3" or 4" pipe and can be used without needing access from below. To install an Oatey Cast Iron Closet Flange: Place it over the pipe so the gasket secures to the pipe. Tighten the integrated fasteners to the pipe to secure the closet flange.
Toilet manufacturers have weighed in on this discussion to recommend that you place tiles beneath the toilet flange. What they recommend is to put the flange on top of the tile, ensuring that the bottom of the flange touches the surface of the tile.
A best practice is to install the toilet flange on top of the finished floor. If you install the toilet flange flush with the finished floor, or even below the finished floor, leak paths will form, because the flange won't be at the correct height to accept the horn at the bottom of the toilet.
PVC flange, the most common type of flange, simply lift it from the outflow pipe. If the flange is metal or glued to the drain pipe and cannot lift out once the bolts are removed, call a licensed plumber to remove it for you.
Caulk keeps your toilet secure the floor, and avoids any chance of injury or toilet malfunctioning. It's actually required by the International Plumbing Code to caulk a toilet to the floor, and now knowing the reasoning behind it, why would you not want to?
Bolt Toilet to Floor
Place a washer and nut on each toilet bowl bolt and tighten evenly the nuts onto the bolts. Alternate from one side of the toilet to the other as you tighten the nuts a little at a time. Be careful not to over-tighten the nuts and crack the porcelain bowl.
Every toilet in your home has a wax ring connecting it to your plumbing, which creates a waterproof seal to keep what goes down to the sewer from seeping out the sides. This piece of equipment usually lasts as long as the toilet, about 30 years.
Reusable: Unlike wax rings, rubber gaskets can be repositioned without losing their sealing capability. Temperature-resilient: Rubber gaskets are less affected by temperature fluctuations. Easy installation: Rubber gaskets are less messy and easier to handle.
If you notice the caulk around the base of your toilet start to turn brown, it means your toilet has a wax ring which is leaking. As a result, human waste especially urine is decolorizing the normally white caulk. The solution to this is to remove the toilet and put a new wax ring.