How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manfuactured and modular homes

Can a trap arm be smaller diameter than the trap under a sink?

Wednesday, March 30, 2022

“A trap shall not be larger than the drainage pipe into which the trap discharges,” according to the International Residential Code (IRC P3201.7). So a trap arm cannot be smaller than the trap.

    But, conversely, a larger trap arm is allowed. "It’s never a problem to go up in drain size as long as the slope is correct,” according to plumber James Freeman, of J.W. Freeman Plumbing in Gainesville, Florida.

• • • • • • • • • • • • • • • • • • • • • • • • • •

Here’s links to some of our other articles about PLUMBING DRAINS AND TRAPS:

Why can't a sanitary tee be used for a horizontal-to-horizontal drain pipe connection? 

 Why is it a problem when a trap under a sink is installed backwards? 

What are the code requirements for plumbing vent terminations?

What are the code requirements for layout of drain piping under sinks?

  What is the difference between a vent stack and a stack vent?

What is a "combination waste and vent" in a plumbing system? 

What is a building trap?  

What is an indirect waste receptor? 

What is the difference between water pipe and sewage (waste) pipe? 

How can I tell if a house is connected to a septic tank system or sewer? 

What is an auto vent, air admittance valve, or check vent?

Can I make a trap under the sink from straight pipe and 90º elbows?  

If all the plumbing drains have water in them and you can still smell sewer gas, what's causing the problem?  

Why is there a flexible accordion pipe under the sink? 


 

Water Heaters

Water Heater Age

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests

Sinkholes

Stairs

When It First

Became Code

"Should I Buy A..."

Park Model Homes

Site

Shingle Roofs

Safety

Stucco

Remodeling

Wind Mitigation

Roof and Attic

"Does A Home

Inspector...?"

Pool and Spa

"What Is The Difference Between..."

Radon

Brick

Plumbing

Concrete and

Concrete Block

Metal Roofs

Foundations

Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants

Condominiums

Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil

Insurance

Floors

Insulation

Toilets

Exterior Walls

& Structures

Generators

Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers

Electrical

Kitchens

Doors and Windows

(placeholder)

Cracks

Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps

Appliances

Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.

Bathrooms

Lighting

AFCI, CAFCI,

DFCI, & GFCI

Sinks

Air Conditioner & Furnace Age/Size

Attics

Electrical Switches

Siding

Search

This

Site

Water Intrusion

Electrical - Old

and Obsolete

(placeholder)

Foundation Certifications

Tiny Houses

About Us

(placeholder)

Wells