How to Fix a Toilet Flange That Is Too High

Signs your toilet flange is too high

A toilet flange that is too high above the finished floor creates a range of noticeable problems. The most obvious sign is that the toilet rocks or wobbles when you sit on it, even after you have tightened the bolts. You might also see gaps between the toilet base and the floor, along with cracked or broken caulk. The wax ring, which seals the toilet to the flange, can fail prematurely because it is not being compressed evenly, leading to water leaks around the base.

If you notice these signs, it is important to address the flange height before the leak causes damage to the subfloor or joists. A leaking toilet wastes water, and per the EPA, toilets are the main source of indoor water use, accounting for nearly 30 percent of an average home's indoor water consumption. Fixing the flange not only resolves the wobble and leaks but also contributes to water efficiency.

Why flange height matters

The toilet flange, also known as a closet flange, serves two critical functions: it connects the toilet to the drainpipe and provides a mounting surface for the wax ring or rubber gasket. The flange should be installed so that its top sits at or slightly below the level of the finished floor. If the flange stands above the floor, the toilet cannot sit flush, and the weight of the toilet rests on the flange rather than on the floor. This creates a rocking motion that breaks the seal.

A proper seal is essential for preventing sewer gas from entering your home and for avoiding water damage. The design of the flange also affects the long-term stability of the toilet, which is why getting the height right is a core part of any toilet installation, as discussed in our guide on toilet flange basics.

Assess the flange height

Before you decide on a fix, you need to determine how much higher the flange is than the floor. Use a straightedge, such as a level, laid across the flange opening and the floor. If the flange is visibly above the straightedge, it is too high. Also check whether the flange is level and free of cracks. For rough-in dimensions, refer to our guide on how to measure rough-in, though the flange itself is usually centered on the drain.

The material of the flange matters. PVC and ABS plastic flanges can be trimmed with common tools, while cast iron flanges are more difficult to modify and may require a different approach. Knowing what you are working with will help you choose the most effective method.

Option 1: Trim a plastic flange

If the flange is made of PVC or ABS and the excess height is moderate, you can trim it down using a hacksaw or a rotary tool with a cutoff wheel. First, remove the toilet and the wax ring to access the flange. Clean the area thoroughly. Then, carefully cut the flange down to the desired height, keeping it level. Take care not to cut into the drainpipe or create splinters that could interfere with the seal.

After trimming, sand the cut edge smooth. Reinstall the toilet with a new wax ring, following the steps in our how to install a toilet guide. This method is the most direct and often the best solution for a plastic flange that is only slightly high.

Option 2: Use shims as a temporary fix

Shimming is a common quick fix that involves placing plastic or rubber shims under the toilet base to level it. While this can stop the rocking, it does not solve the underlying problem of the flange being too high. The gap between the toilet and the floor may still allow the wax ring to be compressed improperly, and over time the shims can shift. Consequently, shims are best used only as a short-term solution until you can perform a proper fix.

If you do use shims, apply a bead of caulk around the base after tightening the bolts to fill any visible gaps. This can help prevent moisture from getting under the toilet, but it is not a substitute for fixing the flange height.

When to replace the flange

If the flange is cracked, warped, or the drainpipe is damaged, trimming may not be enough. In such cases, replacing the flange is the safer option. This involves cutting out the old flange (with a saw or angle grinder) and installing a new one, which may be glued to a PVC pipe or secured with screws into a cast iron hub. This is a more involved project that might require access to the subfloor from below.

The new flange should be installed so that its top is level with the finished floor. If you are replacing an old toilet at the same time, consider checking our buying guides for best 12-inch toilets to find a model that matches your rough-in and comfort needs.

Step-by-step: Fixing a high flange

1. Turn off the water supply and disconnect the supply line. 2. Remove the toilet by unscrewing the nuts on the closet bolts and lifting it straight up. 3. Remove the old wax ring and clean the flange and floor area. 4. Measure the flange height relative to the floor with a straightedge. 5. If the flange is plastic, trim it using a hacksaw or rotary tool, keeping it level. 6. Sand any rough edges and remove debris. 7. Install a new wax ring or rubber gasket, then lower the toilet onto the flange, being careful to align the bolts. 8. Place washers and nuts over the bolts, tighten them evenly, and check for levelness. 9. Reconnect the water supply and test for leaks.

If the flange is metal and cannot be trimmed safely, or if you are not comfortable working around plumbing, consider hiring a professional. The EPA notes that simple repairs like replacing a toilet flapper can save significant water, but flange work can be more involved.

What to pick after fixing your flange

Questions

Can I use a flange spacer to fix a flange that is too high?

No. Flange spacers are designed to raise a flange that sits below the floor level. If your flange is too high, you need to lower it, not add to it.

Is it safe to trim a PVC toilet flange?

Yes, if you do it carefully. Use a fine-tooth saw or rotary tool, and avoid cutting into the drainpipe. Always wear safety glasses and gloves.

Why does my toilet rock even after replacing the wax ring?

A high flange is a common cause. The toilet cannot sit flat on the floor, so it rocks and the wax ring gets compressed unevenly, leading to leaks.

Can I caulk the base of the toilet to hide the gap caused by a high flange?

Caulk can seal the gap temporarily, but it does not fix the underlying height issue. The toilet may still shift, and water can get trapped under the caulk. It is better to address the flange height directly.

When should I call a plumber for a high flange?

If the flange is cast iron, cracked, or the drainpipe is damaged, or if you are unsure how to cut the flange without risking the plumbing, call a licensed plumber. Also, if you do not have the right tools, professional help is safer.