If you’ve ever noticed a bad sewer smell in your home, a dry P-trap could be the reason. The P-trap is a curved pipe under sinks, showers, and toilets. It holds water to block sewer gases from escaping. When it dries out, foul odors can enter your home.
This issue is common in California cities like Fresno, Bakersfield, and Sacramento, where dry weather and aging plumbing systems contribute to dry traps and sewer gas leaks.
In this guide, we’ll explain what causes dry traps and how you can prevent them using simple plumbing maintenance tips. If the problem persists, a cheap plumber Denver can help you fix the issue.
What Causes a Dry Trap?
A dry P-trap loses its water seal, allowing sewer gases to rise into your home. Here are some common reasons this happens:
1. Infrequent Use of Fixtures
If a sink, shower, or floor drain isn’t used often, the water inside the trap can evaporate, leaving it dry.
Solution:
Run water in unused drains once a week to keep the trap filled.
If you have a guest bathroom, flush the toilet and run the sink occasionally.
2. Hard Water Buildup in Toilet Tanks
In cities like Fresno and Bakersfield, hard water deposits build up inside the toilet tank. Over time, this can affect water flow and cause slow refilling of the P-trap.
Solution:
Clean the toilet tank with vinegar to remove hard water deposits.
Install a water softener to prevent future buildup.
3. Leaky P-Traps
A small leak in the P-trap can slowly drain the water, causing it to dry out. This is common in older homes in Sacramento and Riverside.
Solution:
Check under sinks for signs of leaking water.
If the trap is cracked or rusted, replace it immediately.
4. Blocked or Poorly Installed Vent Pipes
Your home’s plumbing system includes vent pipes that help regulate air pressure. If the vent pipe is blocked or incorrectly installed, it can cause water to siphon out of the trap, leaving it dry.
Solution:
If you hear gurgling sounds from drains, your vent pipe may be blocked.
A cheap plumber in Denver can inspect and fix venting issues.
5. Extreme Weather Conditions
In very dry climates like California’s Central Valley, high temperatures increase evaporation, causing traps to dry faster.
Solution:
Pour a cup of mineral oil into the drain after running water. This slows evaporation.
How to Prevent Dry Traps
Keeping your P-traps from drying out is simple and requires regular maintenance. Follow these practical solutions to prevent sewer gas smells in your home.
1. Regularly Run Water in Unused Drains
If you have sinks, showers, or floor drains that aren’t used often, run water through them at least once a week.
Steps:
Turn on the faucet for 15–30 seconds to refill the trap.
If it’s a shower, pour a bucket of water down the drain.
For floor drains, slowly pour a gallon of water to refill the trap.
2. Use Mineral Oil to Slow Evaporation
Mineral oil sits on top of the water in the trap and reduces evaporation.
How to Apply:
Run water down the drain to fill the trap.
Pour about ½ cup of mineral oil into the drain.
This method is especially useful in hot, dry climates like Bakersfield and Fresno.
3. Clean Your Toilet Tank to Prevent Hard Water Issues
Hard water deposits can affect toilet flushing and trap water levels.
How to Clean the Toilet Tank:
Turn off the water supply and flush the toilet.
Fill the tank with white vinegar and let it sit for an hour.
Scrub with a toilet brush and flush.
Repeat this process every 3–6 months to prevent buildup.
4. Fix Leaky Pipes and P-Traps
A small leak in the P-trap can cause the water seal to disappear.
How to Check for Leaks:
Place a dry paper towel under the trap and check for moisture.
If the trap is leaking, replace the washer or install a new P-trap.
If you're not comfortable fixing leaks yourself, a cheap plumber in Denver can help.
5. Inspect and Unclog Vent Pipes
Blocked vent pipes cause water to siphon out of the trap, leaving it dry.
How to Unclog a Vent Pipe:
If you hear gurgling noises from drains, check the vent opening on the roof.
Remove any leaves or debris blocking the pipe.
If the issue persists, hire a plumber to inspect the vent system.
6. Install a Trap Primer for Floor Drains
If you have floor drains in your basement, garage, or laundry room, installing a trap primer can prevent drying.
What is a Trap Primer?
A trap primer is a small device that automatically refills the P-trap with water. It’s great for floor drains that are rarely used.
Installation:
A plumber can install it in areas where dry traps are common.
It’s a good investment for homes in dry climates like California.
Cities in California with Common Dry Trap Issues
Several cities in California experience dry traps due to climate, hard water, or aging plumbing systems. Here are some of the most affected areas:
Sacramento – Older homes with venting problems and leaky traps.
Fresno – High temperatures increase water evaporation in traps.
Bakersfield – Hard water buildup affects toilet tank function.
Stockton – Frequent plumbing issues lead to sewer gas leaks.
Riverside – Dry weather and low humidity dry out P-traps faster.
If you live in these areas and experience recurring sewer smells, consider calling a local plumber for a professional inspection.
When to Call a Plumber
If you’ve tried these preventative measures but still experience sewer smells, it’s time to call a professional. A cheap plumber in Denver or a local plumber in California can:
Inspect and repair leaky P-traps.
Clear blocked vent pipes to prevent trap siphoning.
Install trap primers for floor drains.
Check for sewer line damage if the issue is persistent.
Ignoring dry trap issues can lead to long-term sewer gas exposure, which can be harmful to your health.
Conclusion
A dry P-trap can cause sewer gas smells in your home, but preventing it is simple. By running water regularly, using mineral oil, fixing leaks, and maintaining your hard water toilet tank, you can keep your traps full and prevent foul odors.
If you suspect bigger plumbing issues, don’t wait—contact a cheap plumber in Denver or a local expert in California for a professional inspection.
