Have you shut off the angle stop behind the toilet, flushed to empty the tank, and sponged out the remaining water in both the tank and the bowl?

A full toilet weighs 80+ lb. Empty it before lifting. Have a helper on standby if you're not comfortable lifting awkward weight alone.

With the old toilet removed (or peeking past the base), what is the condition of the closet flange on the floor?

The flange is the round fitting bolted to the floor that the wax ring seats against. Look for cracks, broken bolt slots, or a flange that sits below finished floor level.

Measure from the finished wall behind the toilet to the center of the closet bolts. Does that measurement match the rough-in of your new toilet (typically 12")?

Look at the supply line running from the angle stop to the (old) tank. What does it look like?

Lead-soldered supply lines or rigid chrome with corroded compression nuts are warning signs.

Do you have all of these on hand: new toilet, new wax ring (or waxless gasket), new closet bolts, a new braided supply line, a putty knife or scraper, and a sturdy rag/towel for the old wax?

plumbing troubleshooting

Install a new toilet

Common symptoms: install toilet; replace toilet; new toilet install; wax ring replacement; toilet flange

Stop and call a pro if:

heavy fixture (80+ lb)
potential subfloor damage from prior leaks
sewer gas exposure when bowl is removed

Step-by-step diagnostic flow

Step 1
Have you shut off the angle stop behind the toilet, flushed to empty the tank, and sponged out the remaining water in both the tank and the bowl?
A full toilet weighs 80+ lb. Empty it before lifting. Have a helper on standby if you're not comfortable lifting awkward weight alone.
Step 2
With the old toilet removed (or peeking past the base), what is the condition of the closet flange on the floor?
The flange is the round fitting bolted to the floor that the wax ring seats against. Look for cracks, broken bolt slots, or a flange that sits below finished floor level.
Step 3
Measure from the finished wall behind the toilet to the center of the closet bolts. Does that measurement match the rough-in of your new toilet (typically 12")?
Step 4
Look at the supply line running from the angle stop to the (old) tank. What does it look like?
Lead-soldered supply lines or rigid chrome with corroded compression nuts are warning signs.
Step 5
Do you have all of these on hand: new toilet, new wax ring (or waxless gasket), new closet bolts, a new braided supply line, a putty knife or scraper, and a sturdy rag/towel for the old wax?

Possible outcomes

You're ready — proceed with the install

high confidence

Water is controlled, flange is sound, rough-in matches, supply is serviceable, and you have your consumables.

Safe next steps

Lay an old towel beside the flange to set the bowl on while you work
Scrape the old wax off the flange completely; replace closet bolts
Set the new wax ring on the flange (not the toilet horn) for most installs, or follow the waxless gasket maker's instructions
Lower the new bowl straight down onto the bolts; press evenly to seat the wax
Hand-tighten the closet nuts in alternating turns — do NOT crank, you can crack the china
Mount the tank, connect the new braided supply, turn water on slowly, and flush several times while checking the base for leaks

Pause — replace the angle stop first

high confidence

A shutoff that won't fully close means you can't safely disconnect the supply. That needs to be handled before you commit to pulling the toilet.

Safe next steps

Run the angle-stop-replacement workflow, or shut off the house main and replace the stop now
Once the new stop holds tight, come back and restart this workflow

Angle stop won't shut off completely

Stop — call a pro for the flange

high confidence

A cracked flange, broken bolt ears, or a flange below finished floor level will not seal reliably with a standard wax ring. Repair or replacement involves cutting into the drain or floor.

Safe next steps

Photograph the flange from directly above
Leave the area dry and uncovered for the plumber to inspect

What to document for a pro

Photos of flange
Floor finish type (tile, vinyl, wood)
Whether subfloor is accessible from below

Cracked or broken closet flange. Flange sits below finished floor level

Stop — likely subfloor damage

high confidence

A spongy floor around the toilet usually means a long-running wax-ring leak has rotted the subfloor. Setting a new toilet on a soft floor will lead to another leak and a worse repair.

Safe next steps

Photograph the area around the flange
Do not set a new toilet on the existing floor

What to document for a pro

Photos of soft area
Any visible staining on the ceiling below if applicable

Soft / rotted subfloor around toilet base

Pause — check the new toilet matches your rough-in

high confidence

A 12" toilet on a 10" or 14" rough-in won't fit correctly. Most homes are 12", but older or remodeled homes vary.

Safe next steps

Verify the rough-in spec on the new toilet's box or spec sheet
Exchange for the correct rough-in or buy an offset flange (only if you're confident with that approach)

Rough-in mismatch between floor and new toilet

Pause — measure the rough-in before going further

medium confidence

You don't want to discover a mismatch after the old toilet is out and the bathroom is unusable.

Safe next steps

With the old toilet still in place, measure from the finished wall to the center of the closet bolts
Cross-check that number against the spec on your new toilet's box

Stop — lead or unknown legacy supply

medium confidence

Lead-soldered or unidentifiable legacy supply lines should be evaluated and replaced by a pro before you disturb them.

Safe next steps

Photograph the supply line from the angle stop to the tank
Leave the existing connection alone until a plumber assesses it

What to document for a pro

Photo of supply line and angle stop
House age if known

Lead-soldered or unidentified legacy supply line

Pause — gather missing parts first

high confidence

Starting a toilet swap without the consumables means a half-installed toilet and no bathroom.

Safe next steps

Buy: wax ring (or waxless gasket), closet bolts, braided stainless supply line
Have a putty knife, adjustable wrench, sponge, and towels staged before you start

Diagnostic guidance only. If unsure, stop and call a licensed professional — gas, electrical, and refrigerant work is hazardous to untrained users.

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