What’s Under Your Kitchen Sink? 3 Parts to Check
The P-trap, shutoff valves and dishwasher high loop protect your kitchen. Learn the warning signs and how The Great House fixes them in Northern Virginia.
KITCHEN REMODELING
11/4/20263 min read
ASK MASON · KITCHEN
What’s Under Your Kitchen Sink? 3 Parts That Protect Your Home
Most people never check them. Mason shows what they do, the warning signs, and how we fix them.
Under every kitchen sink are three small parts that protect your home: the P-trap, the shutoff valves and the dishwasher high loop. Most homeowners never look at them until something leaks.
Watch Mason’s video below, then read what each part does, the warning signs to watch for, and how The Great House fixes them before a small drip becomes a new cabinet.
IN THIS GUIDE
01
What’s Under Your Sink
The 3 Parts That Protect Your Kitchen
THE P-TRAP
Holds a little water that blocks sewer gas from your kitchen.
SHUTOFF VALVES
Stop the water in seconds, as long as they still turn.
DISHWASHER HIGH LOOP
Keeps dirty sink water from flowing back into the dishwasher.
The P-trap is the U-shaped pipe under the drain. It always holds a little water, and that water is a seal that stops sewer gas from coming up into your kitchen. If the trap is loose or cracked, it drips. If it dries out, you smell it.
The two shutoff valves, one for hot and one for cold, let you stop the water in seconds. Older valves often seize after years without use, so they won’t close in an emergency, exactly when you need them.
The dishwasher drain hose should loop up high under the counter before it joins the sink drain. Without that high loop, dirty sink water can flow back into your dishwasher.
Mason’s diagram: the P-trap, shutoff valves and dishwasher drain under a kitchen sink
Each part is small and inexpensive. The damage they prevent is not.
02
Warning Signs
Spot the Problem Before It Spreads
DRIPS OR STAINS
Water marks, drips or swollen wood on the cabinet floor.
SEWER SMELL
A loose or dry trap lets sewer gas into the kitchen.
SLOW DRAIN
Water that sits in the sink after it should be gone.
These problems start small. A slow drip inside the cabinet soaks the cabinet floor, swells the wood and grows mold, often for months before anyone notices.
By then the fix isn’t a part anymore. It’s a new sink cabinet, and sometimes the floor under it.
Check this today
Open the cabinet with a flashlight. Look for stains or soft wood, sniff for a sewer smell, and try turning each shutoff valve. If a valve won’t turn by hand, don’t force it. Call us instead.
03
How We Fix It
A Quick Visit Now, or a New Cabinet Later
We check every connection under the sink. Then we tighten or replace the P-trap, swap old shutoff valves for new quarter-turn valves, and set the dishwasher hose in a proper high loop.
Caught early vs. caught late
Caught early, it’s a quick visit. Caught late, it’s a new sink cabinet, and sometimes the floor beneath it.
In Northern Virginia
Many Northern Virginia homes are 40 to 60 years old. In Arlington, about 45% of homes were built before 1970 (U.S. Census, 2019–2023). In homes that age, the original shutoff valves under the sink are often decades old and rarely turned. We solved this exact problem on our N Culpeper St renovation in Arlington.
Planning a bigger project?
Planning a full kitchen remodel? We replace all three parts in every kitchen we build, so your new cabinets start dry. See prices and real projects on our kitchen remodeling page.
The fix: a new P-trap, quarter-turn shutoffs and a high dishwasher loop
ASK MASON · KITCHEN
Want to know another problem?
SPOTTED ONE OF THESE SIGNS?
We’ll check it before it turns into a big repair
Free in-home visit from a Class A licensed team. We look under the sink and around your kitchen, then give you a clear written plan.
ABOUT THE AUTHOR
The Great House team
Written by the team at The Great House LLC, a Class A licensed builder and remodeler in McLean, VA (License #2705197237). We have renovated 30+ Northern Virginia homes since 2022.
PLANNING A PROJECT?
Our kitchen remodeling service
See prices, real photos and how we work: our kitchen remodeling page. Real example: Ridgeway Dr kitchen and full renovation.
Serving McLean, Vienna, Great Falls, Fairfax, all of Northern Virginia.