Wobbly Toilet? Loose Bolts, an Uneven Floor, or a Broken Flange

The short answer

A toilet that rocks when you sit on it in a Northern Virginia home is one of three things: loose bolts at the base, a floor that isn’t flat, or a broken flange under the toilet. The first two take about ten minutes. The third means pulling the toilet. Don’t let any of them ride, because every rock breaks the wax seal under the toilet a little more, and a wobbly toilet today is usually a toilet leaking at the base later.

Check the bolts first

Pop the plastic caps off the two bolts at the base. Snug each nut a quarter turn at a time, switching sides, until the toilet stops moving. Hand tight and a little more is plenty. Porcelain cracks if you lean on the wrench. If a bolt spins without tightening, or the toilet still rocks with both nuts snug, it isn’t the bolts.

Shims for an uneven floor

Old floors and tile floors are rarely dead flat. If the toilet rocks side to side but the bolts are tight and the floor has never been wet, slide plastic toilet shims under the low side until it sits solid, snap off the extra, and snug the bolts again. Use plastic, not wood, which soaks up water and swells. Shims are the right fix for a level problem. They’re the wrong fix for a broken flange, because the toilet still isn’t held down.

When it’s the flange

The flange is the ring at the top of the drain pipe, fastened to the floor. The two bolts at the base hook into slots on it, and they’re what hold the toilet down. When it fails, nothing else will keep the toilet still. Old cast iron flanges rust through. Plastic ones crack at the bolt slots. Either way the bolt slips loose, and the toilet starts to rock.

A broken flange usually doesn’t mean a new drain pipe. Depending on what’s under there, the fix is a repair ring or a metal repair plate screwed over the broken section, a new flange, or an extender when a new floor raised the bathroom. The flange should sit on top of the finished floor, not under it. Every one of these needs the toilet pulled and a new wax ring, and most are done in one visit.

Why a little wobble is worth fixing

The wax ring that seals the toilet to the drain only works if the toilet doesn’t move. Once a rock breaks it, some water from every flush goes into the floor instead of the pipe, and you won’t see it for weeks. Toilet leaking at the base goes through how to tell that’s happening and what it takes. Caught at the wobble, it’s a toilet reset. Caught at the soft floor, it’s a bigger job.

What not to do

• Don’t keep tightening the nuts on a toilet that won’t stop rocking. That’s how the base cracks.
• Don’t caulk a wobbly toilet to hold it still. Caulk hides a leak, it doesn’t hold anything down.
• Don’t stack two wax rings to make up for a low flange. It’s a common repeat leak.
• Don’t use wood shims. They soak up water and rot.

While we’re there, a worn fill valve or flapper takes a few more minutes. If the toilet has been refilling by itself, mention it, and it’s done in the same visit. If the toilet is old enough to use 3.5 gallons a flush, how much water an old toilet uses does the math on replacing it instead.

A rocking toilet is one of the small signs worth catching. Every warning sign around the house, from a furnace’s blinking light to the sounds a house makes, is in one guide.

Fix it small, fix it now

A leak caught early is cheaper three ways. The water and sewer bill stops climbing. The water stops soaking the subfloor or the ceiling under it. And it stays a small repair, a part and an hour, instead of a bigger one later. Almost everything we find wrong with a toilet is repairable, and once it’s fixed right, you stop checking the floor every time you walk in.

What it costs when we fix it

Most leaks, wobbles and fill problems are a repair, toilet repair at $250 to $900, with the price in writing before we start. That covers a wax ring, a flange repair, tank bolts and gaskets, and fill valves. When the toilet itself is cracked or worn out, a new one installed runs $800 to $1,300, and this month’s coupons on our offers page take $100 off a new toilet, or $50 off any plumbing repair over $400. Any plumbing repair also comes with a whole-house plumbing inspection, a $149 value. If you can’t tell where the water is coming from, leak detection runs $200 to $500. A plumbing diagnosis visit is $49, or $250 after hours.

Call (703) 997-9757, day or night, or book a toilet repair online. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.

Questions people ask

Why does my toilet wobble?

Loose bolts at the base, a floor that isn’t flat, or a broken flange under the toilet. Snug the bolts first. If it still rocks, shim it or check the flange.

Is a wobbly toilet dangerous?

Not to you, but to the floor. Each rock breaks the wax seal a little more, and a broken seal leaks dirty water into the subfloor with every flush.

Can I fix a wobbly toilet with shims?

Yes, if the bolts are tight, the floor is dry and the flange is sound. Use plastic shims. Shims don’t fix a broken flange.

How do I know if my toilet flange is broken?

A nut spins and won’t tighten, the toilet rocks with the bolts snug, or water shows at the base. With the toilet off, you’ll see a crack or rust at the bolt slots.

How much does it cost to fix a toilet flange?

When we do it, a flange repair and a new wax ring are a toilet repair, $250 to $900, priced in writing before we start.