Bathroom remodels are expensive enough without avoidable plumbing mistakes. Here are the big ones.
Bathroom remodels are where good plans meet harsh reality. The plumbing is usually the biggest source of surprise costs and delays. Here's how to avoid that.
Mistake 1: Not Involving a Plumber Early
People design their dream bathroom, buy all the fixtures, start demo, THEN call a plumber. Who tells them half of what they want isn't possible without major work.
Get a plumber involved during design. They'll tell you what works with your existing plumbing, what requires moving pipes (expensive), and what's flat-out not possible without tearing into the floor below.
Cost of this mistake: $2,000-10,000 when you have to return fixtures, redesign, and redo work.
Mistake 2: Moving the Toilet
Toilets drain through a 3-4 inch pipe that goes through your floor. Moving a toilet means breaking through the floor, relocating this pipe (which requires proper slope), and potentially affecting the room below.
If you're on a concrete slab, it's even worse—you're jackhammering concrete and routing new pipes in the slab.
Moving a toilet adds $800-2,500 to your project. Keep it where it is unless you have a really good reason.
Mistake 3: Choosing Fixtures Before Checking Rough-In Dimensions
That beautiful modern tub you fell in love with? It might not fit your existing drain location. That rainfall showerhead? Might require relocating the shower arm, which means opening walls.
Before you buy anything:
- Measure existing rough-in locations (where pipes come through walls/floor)
- Check fixture spec sheets for required rough-in dimensions
- Make sure they match, or budget for relocating pipes
Mistake 4: Ignoring Vent Requirements
Every drain needs a vent. Vents allow air in so water can drain properly and keep sewer gases out of your house. They're required by code, but people forget about them because they're hidden in walls.
Adding a new sink or moving one often requires adding or extending a vent. That means opening walls, running pipe up through the roof, and coordinating with your roofer to flash it properly.
Venting adds $300-1,500 depending on complexity. Budget for it.
Mistake 5: Tile Before Final Plumbing
Sequence matters. Rough plumbing (pipes in walls) happens early. But finish plumbing (installing faucets, showerheads, drains) happens after tile.
If your tile guy cuts holes in the wrong place or doesn't leave proper clearance, your plumber can't install your fixtures. Now you're chipping out tile and redoing it.
Have your plumber mark fixture locations before tile goes in. Better yet, have them there when the tiler is working.
Mistake 6: Skimping on Water Pressure
You want a rain showerhead, body sprays, and a handheld wand. Awesome. Does your water pressure support all of that running simultaneously?
Multiple high-flow fixtures require good pressure and flow rate. If your house has borderline pressure, you'll need a pressure booster pump ($800-1,500 installed).
Or you'll end up with an expensive shower system that delivers a disappointing dribble.
Mistake 7: DIY Plumbing to Save Money
I get it—plumbers are expensive. But bathroom plumbing is not the place to learn DIY skills.
A leak behind your tile means ripping out tile, fixing the leak, and re-tiling. A drain installed at the wrong slope won't drain properly and you won't know until after everything's finished.
Do the demo yourself. Paint yourself. Hire professionals for plumbing, tile, and electrical. The savings aren't worth the risk.
Mistake 8: Not Replacing Old Pipes While Walls Are Open
If your house is 30+ years old and you're tearing into walls anyway, replace the supply lines to that bathroom. You've already paid for access—the incremental cost is small.
Costs maybe $300-600 extra. Prevents having to tear into your beautiful new bathroom in three years when those old pipes fail.
Mistake 9: Inadequate Shut-Off Valves
Install individual shut-off valves for every fixture: toilet, sink, shower. This lets you isolate problems without shutting off water to the whole house.
Use quality ball valves, not cheap gate valves that corrode shut. Costs a bit more but they actually work when you need them.
Mistake 10: No Access Panels
Plumbing fails eventually. When it does, you need access. If your plumber has to cut through tile to reach a valve or leak, you're paying for tile repair.
Install access panels for shower valves, tub drains, and anywhere pipes run. They're $20-100 for a nice recessed panel. Future you will be grateful.
Budget Reality Check
Plumbing is typically 15-20% of a bathroom remodel budget.
$10,000 remodel = $1,500-2,000 for plumbing
$25,000 remodel = $3,750-5,000 for plumbing
If you're moving fixtures, add 30-50%. If you're on a slab or have complex layouts, add more.
Always add 15-20% contingency for unknowns. Old houses hide surprises. You'll find them when you open walls.
