On a low toilet flange, the best fix is raising the flange with spacers or an extender so a standard wax ring seals. If you can't, use an extra-thick wax ring. Don't stack wax rings. A waxless seal can work, but Oatey warns some may not fit every flange height or seal well on uneven or damaged surfaces.
Where should the flange sit?
On top of the finished floor, or even with it. Oatey, one of the biggest makers of wax rings and flanges, says "The flange should sit on top of or even with the finished floor. This placement ensures a proper wax ring seal and prevents leaks." It adds that "The outer ring of the flange should rest on the finished floor surface."
When the flange sits lower, Oatey warns that "Leak paths will form because the flange is not at the correct height to accept the horn at the bottom of the toilet." The horn is the outlet on the bottom of the bowl. It has to press into the seal with enough force to close every gap.
So a low flange is the real problem. The seal you choose is how you work around it.
What are my options for a low flange?
There are three, and Oatey's guidance ranks them fairly clearly.
### 1. Raise the flange (the best fix)
If you can, bring the flange up to the floor. Oatey says that if you can't install the flange on top of the finished floor, "you can use Set-Rite® Toilet Flange Spacers that mount on top of the existing flange." It describes its flange extension kits as "a watertight solution for raising the toilet flange during a remodel," letting you extend the flange surface above the finished floor "for optimum sealing with a standard wax ring."
On a PVC flange, Oatey says PVC spacers are solvent-welded to the flange, or sealed with 100% silicone.
This also fixes the root cause. Once the flange is at the right height, any standard seal has a fair chance.
### 2. Use an extra-thick wax ring
If raising the flange isn't practical, a thicker ring can make up a small gap. Oatey says, "If the flange is set below floor level or on the subfloor, choose an extra-thick wax ring or use flange spacers to accommodate height differences." It sells extra-thick rings made for flanges set below floor level, and a larger ring it describes as made with 40% more wax than its standard ring for flanges "even or slightly below finished floor height."
### 3. Never stack two wax rings
This is the shortcut that causes the most leaks. Oatey is direct about it: "Stacking wax rings is not recommended. Use an extra-thick wax ring or raise the flange height with a spacer kit for better sealing and lasting performance."
Wax vs. waxless: how do they compare?
Both can seal a toilet. They do it in different ways.
A wax ring is compressed between the toilet and the flange. Oatey says wax rings are made from petroleum wax that is soft and moldable, "allowing it to fill gaps from uneven surfaces during installation." Its list of pros includes proven performance, low cost and a durable seal "when properly installed." The cons: wax "may melt or deform in high temperatures," and wax rings "can get misaligned or damaged if the toilet isn't set correctly the first time."
A waxless seal is made from rubber or foam. Oatey says it uses a gasket "that adapts to the flange and floor height," and the rubber "can flex and adapt to slight movements." Its pros are no mess, the ability to reset the toilet, and less effect from temperature. The cons Oatey lists:
- Higher cost. Non-wax gaskets cost more.
- Fit sensitivity. They "May not work with all flange heights or toilet designs."
- Chemical sensitivity. Some can degrade when exposed to certain cleaning chemicals.
- Unproven longevity. "Their long-term durability is not as well-documented as wax rings."
Oatey's wax ring guide adds one more point that matters for low flanges. It says wax-free seals may not seal well on uneven or damaged surfaces, and "may not reliably seal damaged or uneven flanges."
### So which should I use on a low flange?
Here's how we'd put it together:
| Your flange | Best choice |
|---|---|
| Even with or above the finished floor | Standard wax ring or a waxless seal made for your toilet |
| Slightly below the floor | Raise it with spacers, or use an extra-thick wax ring |
| Well below the floor | Raise the flange with spacers or an extension kit |
| Cracked, loose or uneven | Repair the flange first, then seal |
| Any height | Never stack two wax rings |
A waxless seal can make sense when the flange is at the right height and you expect to pull the toilet again soon, such as during a remodel. Just check that the seal is rated for your flange height before you buy it.
Does code say anything about the seal?
Yes. Phoenix's adopted plumbing code, Section 405.4, says connections between the drain and floor-outlet fixtures "shall be made with a floor flange or a waste connector and sealing gasket." Where a waste connector and sealing gasket is used, it must pass the joint tightness test of ASME A112.4.3 and be "installed in accordance with the manufacturer's instructions."
The code also says "The flange shall be attached to the drain and anchored to the structure," and that floor-outlet fixtures must be secured to the floor or flange "by screws or bolts of corrosion-resistant material."
Oatey makes the same point about anchoring. It says the flange "must be fastened securely to the floor, not just the toilet," because without that, "Movement can break the wax seal, allowing sewer gas or leaks." A flange that rocks will break any seal, wax or not.
What else should I check before setting the toilet?
- The flange itself. A cracked ring or broken bolt slot has to be fixed first. See how to fix a broken toilet flange.
- The drain size. Oatey says most standard toilets in the U.S. use a 3-inch or 4-inch wax ring, and the key is measuring the drainpipe opening after the toilet is off.
- A fresh seal every time. Oatey says "If you remove your toilet for any reason, always install a new wax ring to protect against leaks." Its flange guide adds that a compressed wax ring can't be reused, even minutes after you set it.
- New bolts. Oatey says old bolts should be replaced too, since they may be corroded.
### Signs the seal has already failed
Oatey says to replace the wax ring if you notice persistent sewer odors near the toilet. Water on the floor around the base, a toilet that rocks, or stains on the ceiling below are other signs. If you're shopping for a new toilet at the same time, check the rough-in too. See how to measure a toilet rough-in before buying one.
If your flange is low, cracked or loose, HQ can raise or repair it and reset the toilet so it stays sealed. We're licensed and insured, and every estimate is free with upfront pricing.