New flooring is great until you go to reset the toilet and find the flange sitting a quarter inch or more below the new surface. A low flange is one of the most common causes of slow, hidden leaks under toilets, because a standard wax ring simply cannot compress far enough to seal the gap. The fix is cheap and usually takes under an hour, but it is worth doing properly the first time so you are not pulling the toilet again next year.
How high should a toilet flange be?
The flange is the ring fastened to the floor that the toilet bolts to and the wax ring seals against. The widely accepted target is for the top of the flange to sit level with the finished floor or up to about 1/4 inch above it. Manufacturers design their wax rings and the horn on the bottom of the toilet around that range. When the flange sits below the floor, the horn may not reach into the wax far enough and the seal becomes thin and fragile.
Why low flanges happen
- Tile, stone or a new underlayment raised the finished floor
- The flange was set on the subfloor before any flooring was planned
- An old flange has corroded or cracked and sagged
- A remodeler removed old flooring and set the flange too low
Options compared
Pick the fix based on how far below the floor the flange sits. Measure from the finished floor to the top of the flange at several points.
| How far below | Common fix | Typical parts cost |
|---|---|---|
| Up to about 1/4 in | Extra thick wax ring or ring with horn | Usually under $15 |
| About 1/4 to 1/2 in | Flange spacer or extender kit | Usually $10 to $30 |
| Over 1/2 in | Stacked spacers or a new flange at the right height | Usually $20 to $80 DIY |
| Cracked as well | Repair ring plus spacer | Usually $15 to $40 |
If the flange is also broken, read toilet flange repair rings first.
Step by step: fitting a flange extender
- Shut off the water, flush, and sponge out the tank and bowl.
- Disconnect the supply line and remove the bolt nuts.
- Lift the toilet straight up and set it on cardboard.
- Stuff a rag in the drain to block gas and dropped screws, then scrape off all old wax.
- Dry-fit the extender and new closet bolts. Check the top now sits level with or slightly above the floor.
- Run a bead of silicone between the old flange and extender for a watertight join.
- Screw the extender through into the subfloor using corrosion-resistant screws.
- Remove the rag, fit a single standard wax ring or a waxless seal, and lower the toilet straight down.
- Tighten nuts evenly, reconnect water, and check for leaks over the next few flushes.
Why not just stack two wax rings?
It is tempting, and some people get away with it, but two rings can slide against each other as the toilet settles and open a leak path. Plumbers generally prefer an extender or a single thick ring. Waxless seals with stackable spacers are another reliable option; see wax ring vs waxless seal.
Signs a low flange is already leaking
Watch for a toilet that has started to rock, staining or loose grout around the base, a sewer smell, or a soft floor. If you see these, check the subfloor for rot while the toilet is off. A brown ring at the base may be a seal leak rather than surface mess; urine stain around base of toilet explains how to tell.
After the fix
Once the toilet is back, check for any rocking on the floor and shim if needed. Then seal the base as described in caulk around toilet, leaving a small gap at the back so any future leak can show.
Code and safety notes
Most codes require the toilet to be firmly secured to the floor and the flange to be properly fastened. Use brass or stainless bolts and screws in wet areas. Toilets are heavy and awkward, so lift with your legs or get help. Wear gloves when handling old wax.
Tools and materials checklist
Gather everything before you lift the toilet so it is not sitting on the floor for hours: an adjustable wrench, a putty knife or plastic scraper, a tape measure and straightedge, a drill with a masonry bit if the floor is concrete or tile, corrosion-resistant screws, new closet bolts, the extender kit, a wax ring or waxless seal, silicone, rags, gloves and a bucket with a sponge.
Frequently asked questions
Can I use two wax rings?
It is not recommended. Use an extender kit or a single extra thick ring.
Does a low flange cause leaks?
It can. The wax may not seal fully, letting water seep under the floor.
How do I measure flange height?
Lay a straightedge across the finished floor over the flange and measure down to the flange top.
Can I fix a low flange myself?
Yes. Extender kits are designed for DIY and need only basic tools.
Should the flange sit on top of tile?
Ideally yes, at or slightly above the finished surface.