How to Install a New Toilet
Modern toilet installation is a 90-minute DIY job if you know the four common mistakes that cause leaks. We’ll walk you through it.
TL;DR
New toilet installation is straightforward IF you (1) measure rough-in correctly, (2) replace BOTH the wax ring and closet bolts, (3) avoid over-tightening, and (4) test for leaks before stowing the supply line. The whole job runs 90 minutes for a competent DIYer. Most failures we see are from skipped seals or over-tightened bolts cracking the porcelain.
What’s in this guide
- Measure rough-in
- Tools and materials
- Remove old toilet
- Install new toilet
- Connect water and test
- Common mistakes
Toilet installation looks intimidating because of the weight (50–80 lbs) and the consequences of getting it wrong (a slow leak under the wax ring rots subfloor for years). But the procedure is actually simple if you don’t skip steps. Here’s exactly how we do it on real LA service calls.
Tools & Materials You’ll Need
Tools
- Adjustable wrench
- Level
- Putty knife
- Sponge and bucket
- Penetrating oil (for old closet bolts)
- Towels
Materials
- New toilet (most common rough-in: 12 inches)
- New wax ring with horn ($6) — DO NOT reuse the old one
- New closet bolts ($4)
- New supply line — braided stainless ($12)
- Plumber’s putty (optional, for some installs)
- Toilet shims ($3) — for uneven floors
Step-by-Step Instructions
Measure the Rough-In
The “rough-in” is the distance from the wall behind the toilet to the center of the closet flange (the ring on the floor where the toilet bolts down). 12 inches is standard. 10-inch and 14-inch are also common. Measure carefully — buying a 10-inch toilet for a 12-inch rough-in leaves a gap behind the tank that looks bad and can complicate plumbing.
Shut Off Water and Drain Old Toilet
Close the supply valve at the wall. Flush the toilet to drain the tank. Use a sponge to remove remaining water from tank and bowl. Disconnect the supply line at the tank. Have a towel ready — there will be drips.
Remove Old Toilet
Remove the decorative caps over the closet bolts. Loosen and remove the nuts. Rock the toilet gently to break the wax-ring seal, then lift straight up — DON’T tip or drag. Set on cardboard or an old towel. The smell of wax will be unpleasant.
Clean the Flange and Inspect
Scrape off old wax with a putty knife. Inspect the closet flange (the round ring on the floor). It should be flat, intact, and slightly above the finished floor surface. Cracked flanges need replacement before installing the new toilet — don’t skip this. Stuff a rag into the drain to block sewer gas during the install.
Set New Closet Bolts and Wax Ring
Insert new closet bolts into the flange slots. Some bolts have washers/nuts that hold them in position; others use the included plastic retainers. Press the wax ring firmly onto the bottom of the new toilet (NOT the flange) — wax-side down on the flange afterward. Many plumbers prefer mounting the wax ring on the toilet for easier alignment.
Set the Toilet on the Flange
Lift the toilet, align the bolts with the holes in the toilet base, and lower straight down — DON’T rock or tilt. Press firmly until the toilet sits flush against the floor. Apply your full body weight briefly to seat the wax ring. Don’t lift the toilet again — once it’s set, leave it.
Tighten Bolts (Carefully)
Hand-tighten the nuts on the closet bolts first. Then alternating sides, snug them with a wrench — JUST enough to stop any rock. STOP as soon as the toilet feels solid. Over-tightening cracks porcelain and is the #1 reason new toilets crack within months of installation.
Connect Supply Line and Test
Attach the new braided stainless supply line — finger-tight at the toilet first, then 1/4 turn with a wrench. Same at the shutoff valve. Slowly open the supply valve. Watch for any water at the connections — fix any leaks immediately. Once tank fills, flush 3 times and watch the toilet base on the floor for any sign of water.
In 90% of toilet installations we troubleshoot, the original homeowner tried to reuse the old wax ring or skipped replacing the closet bolts. Both materials are designed to be one-use. A wax ring compresses permanently the first time it’s seated; reusing it produces an imperfect seal that leaks over months and rots subfloor. Old closet bolts are usually corroded and shear during tightening. Total cost of new wax ring + bolts: under $10. Always replace both.
Don’t over-tighten closet bolts
Cracking the porcelain base of a brand-new toilet is the most common installation failure we see. Tighten until snug, not crank-down tight. The toilet doesn’t need to be bolted to the floor like a building anchor — it just needs to not rock.
Real Scenarios from Our LA Service Calls
1962 Mid-Century Toilet Install
Homeowner had installed a new TOTO low-flow toilet 6 weeks earlier and noticed a slow stain spreading on the bathroom ceiling below. Investigation revealed they’d reused the original wax ring (assuming it was fine since it looked intact). We pulled the toilet, replaced the wax ring with a new one with horn, replaced corroded closet bolts, set the toilet correctly, and the leak stopped. Subfloor had minor water damage from 6 weeks of slow leaking — patched but should be monitored. Total: $385 plus subfloor inspection.
When to Call a Plumber Instead
DIY isn’t always the right call. Bring in a licensed plumber if any of these apply:
- The closet flange is cracked or below floor level
- You’re unsure about rough-in measurement
- Subfloor under the toilet shows water damage or rot
- You don’t have access to a working main shutoff
- You’re replacing a toilet in a multifamily/condo setting where leaks affect neighbors below
Frequently Asked Questions
How long does a wax ring last?
In a properly installed toilet that doesn’t move: 20–30+ years. In a toilet that rocks: 2–5 years. The wax doesn’t actually wear out — it fails when the toilet shifts and breaks the seal.
Can I install a wall-hung toilet myself?
Wall-hung toilets require an in-wall carrier mounted to studs and a wall-mounted flush plate. Significantly more complex than floor-mount installation. Most homeowners hire a plumber for this — figure $1,200–$1,800 installed in LA.
What’s the difference between a 12-inch and 10-inch rough-in toilet?
12 inches is standard for most homes built post-1960. 10 inches is used in older LA homes and some retrofits. 14 inches is rare. Buying the wrong size leaves a visible gap behind the tank or won’t fit at all.
Do I need plumber’s putty?
Generally no for the wax ring (wax does the sealing). Some installers add a thin bead of plumber’s putty around the toilet base for cosmetic sealing — that’s optional. Don’t use silicone caulk all the way around — leaving the back gap unsealed lets you spot a leak before it damages subfloor.
How much should toilet installation cost?
DIY: $25–$60 in supplies + your time. Professional in LA: $185–$385 for installation only (toilet supplied by you). Toilet + installation: $450–$900 for standard, $700–$1,500 for premium.
Need professional help in Los Angeles?
Same-day service. Flat-fee pricing. No surprise add-ons.
Call (818) 938-8660
