Reuben's Home Inspection Blog


Stinky Laundry Room? Stinky Bathroom? Check Your Traps.

Have you noticed any foul odors in your basement that you just can't get to the bottom of?  It might be sewer gases coming in to your home.  Every plumbing fixture needs to be equipped with a trap, which is basically a dip in a pipe that water fills up.  This water sitting in the trap is what prevents sewer gases from coming in to your home.  The photo below shows a "P-trap" - this is the type of trap you'll find below sinks, showers, and bath tubs.

P-trap explained

Toilets have their own built in traps, and so do floor drains.  The trap on a floor drain is located below the surface of the floor - the photo below shows a floor drain as seen from the side.

Floor Drain

The problem that home inspectors often find in basements is that floor drains or other plumbing fixtures in the basement never have any water flowing to them, so the water in the trap eventually dries out and allows stinky, hazardous sewer gas to come in to the home.  Because of this, abandoned or shut off plumbing fixtures are always listed as a hazard or required repair on Truth-In-Sale of Housing evaluation reports in Minneapolis, Saint Paul, and the rest of the surrounding cities.

P-trap with no water

Floor drains are the most frequent offenders.  If a floor drain doesn't have water flowing to it on a regular basis, the water in the trap will dry out.  A few common things that regularly drain to floor drains and help prevent the traps from drying out are AC condensate drain lines, high efficiency furnace condensate drain lines, humidifier drain lines, dehumidifier drain lines, HRV drain lines, and water softener discharge lines.  If you don't have anything draining to your floor drain on a regular basic, the water in the trap may evaporate.

rv antifreeze

One fix is to pour some RV antifreeze in to the drain.  RV antifreeze is cheap, sold everywhere, safe for the environment, and it won't evaporate.  It's made just for this kind of thing.  Another option is to periodically pour some water down the drain; you'll obviously need to do this on a regular basis, but it's free and easy to do.
Basement toilets are another frequent offender.  These are typically found in old Minneapolis and Saint Paul homes, and it consists of a toilet sitting out in the middle of the basement, with no privacy offered.  These toilets don't get much use, and the water in the bowl eventually dries out.

If you have an abandoned toilet in your basement, have it removed and have the opening to the sewer capped off.

Abandoned standpipes can be another source of sewer gases.  A standpipe is a stand-alone trap that typically receives the discharge water from a washing machine.  If the washing machine gets moved and is not longer discharging to the standpipe, the water will eventually evaporate.

Standpipe diagram

The fix for an abandoned standpipe is to cap it off or remove it.

Infrequently used bathrooms are the final common offender.  In larger homes with guest bathrooms that never get used, the water in the sink, toilet, or tub / shower can evaporate.

As with floor drains, the fix is to pour some RV antifreeze in to the fixtures, or remember to run some water through them every few months.  Easy.

Reuben Saltzman, Structure Tech Home Inspections


Comment balloon 32 commentsReuben Saltzman • August 22 2012 03:44AM


Great tip....and one more thing to add to the initial walk thru for a listing that may have such a problem.

Posted by Sally K. & David L. Hanson, WI Realtors - Luxury - Divorce (EXP Realty 414-525-0563) over 6 years ago

Good morning Reuben,

As usually you have the most informational tips! Your title is right on..many a time an inspector has noticed evidence of no P-trap in under a sink and that it why there is an odor!! Congrats on the feature..well deserved!!

Posted by Dorie Dillard CRS GRI ABR, Serving Buyers & Sellers in NW Austin Real Estate (Coldwell Banker United Realtors® ~ 512.750.6899) over 6 years ago

Reuben, great information, and even better for most of us, pragmatic solutions...

Posted by Chris Smith, South Simcoe, Caledon, King, Orangeville Real Esta (Re/Max Chay Realty Inc., Brokerage) over 6 years ago

I'm definitely bookmarking this.  I've been to several homes that people are about to buy/just closed on that I think have these issues because either no one has been living there for a while an older person has and they haven't used items in the basement.  This makes perfect sense.  Thx.

Posted by Debbie Gartner, The Flooring Girl & Blog Stylist -Dynamo Marketers (The Flooring Girl) over 6 years ago

Reuben, i always tell people to run the water in their tubs they never use at least every other week...or they get that stinky smell!

Posted by Ginny Gorman, Homes for Sale in North Kingstown RI and beyond (RI Real Estate Services ~ 401-529-7849~ RI Waterfront Real Estate) over 6 years ago

always loved the non privacy basement toilet at my Grandma's. Quite a sight to be sent to the freezer for some corn and see my Grandpa sitting there with a newspaper like nothing was wrong in the world.  

Posted by Scott Seaton Jr. Bourbonnais Kankakee IL Home Inspector, The Home Inspector With a Heart! (SLS Home Inspections-Bradley Bourbonnais Kankakee Manteno) over 6 years ago

I have smelled that "smell" before in bathrooms.  Thank you for the tip!  It will be helpful with vacant homes, etc.

Posted by Joy Daniels (Joy Daniels Real Estate Group, Ltd.) over 6 years ago

Thank You so much for the great tip, I have a listing that's been vacant and what do you know?? It has that awful smell you described.

Posted by Beth Atalay, Cam Realty of Clermont FL (Cam Realty and Property Management) over 6 years ago

Reuben, a very good tip for keeping the drains odor free. Using RV antifreeze is also a good tip.

Posted by Michael Setunsky, Your Commercial Real Estate Link to Northern VA over 6 years ago

So, is that what smells? Great post and a must read for all home owners.

Posted by Harry F. D'Elia, Investor , Mentor, GRI, Radio, CIPS, REOs, ABR (Real Estate and Beyond, LLC) over 6 years ago

I can distinctly remember some homes that I have visited that when you enter the laundry room/bath, you get the smell. shortly after that, traps came into my radar...and a more experienced agent was education continues with your post...thank you

Posted by Richie Alan Naggar, agent & author (people first...then business Ran Right Realty ) over 6 years ago

I have actually run into this in my own house years ago with a downstairs bathroom that was rarely used.  I learned long ago that every few weeks to pour a bucket of water down the drain.  Problem solved.

Posted by Chris and Dick Dovorany, Broker/Associate at Premiere Plus Realty ( Homes for Sale in Naples, Bonita Springs and Estero, Florida) over 6 years ago

Great post and an important tip. One could search a stinky house for odor source for hours and never realize where it's coming from!

Posted by Vanessa Saunders, From Manhattan to the Catskills of New York (Global Property Systems Real Estate) over 6 years ago

great post and tips if all else fails check the water quality :)

Posted by Ashley Connolly (Northeast Water Wells Inc) over 6 years ago
Great point, I used to own a mechanical plumbing company, another liqquid that is usually on hand that works well on a dry floor drain, is cooking oil, it does not evaporate like water will.
Posted by Ann Samuelson (Suntree Inc.) over 6 years ago

You wrote this at the perfect time for me.  We have been dealing with this issue - but it's in our master shower which is used twice a day.  My husband has tried everything . . . except for the antifreeze which I will buy today.   Hope it works! 

Posted by Margaret Goss, Chicago's North Shore & Winnetka Real Estate (Baird & Warner Real Estate) over 6 years ago

Reuben, I had a seller meet us at the door one time and the first thing he said was to warn us about the "unexplained" odor in the basement that they had supposedly even had a plumber in to figure out to no avail.  It was simply the abandoned washing machine drain :)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 6 years ago

Great advice. Unless you are showing properties where the agent, broker, and buyers all have serious head colds. And are breathing through their mouths.

Posted by Andrew Mooers | 207.532.6573, Northern Maine Real Estate-Aroostook County Broker (MOOERS REALTY) over 6 years ago

It's a stinky job, but somebody has to do it.  Better that than clients rushing out of the home.  Didn't know that about the anti freeze....

Posted by Sandy Acevedo, RE/MAX Masters, Inland Empire Homes for Sale (951-290-8588) over 6 years ago

Love it!  Drains can dry?  Gee, who knew!  Those little brown guys look mean!

You forgot to mention duct tape.  That could solve the problem too!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 6 years ago

Reuben, Great post. Trap primers are also an answer but a litlle more costly.


Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) over 6 years ago

Sewer gas stinks! I hate the smell of it in vacatn homes.

Posted by Erica Ramus, MRE, Schuylkill County PA Real Estate (Erica Ramus - Ramus Realty Group - Pottsville, PA ) over 6 years ago

Very interesting.  I think many homeowners think things go down and that's the end of it. . .until they don't:-)  You offer great tips and solutions for a stinky problem.

Posted by Myrl Jeffcoat, Greater Sacramento Real Estate Agent (GreatWest Realty) over 6 years ago


I have learned so much from the property inspectors on ActiveRain.  I have the answer to my question, why is that basement drain so smelly.  Now I know what to do with it.

Posted by Evelyn Kennedy, Alameda, Real Estate, Alameda, CA (Alain Pinel Realtors) over 6 years ago

Sally and David - on vacant houses, absolutely.

Dorie - I just found that at an inspection on monday; big house, recently remodeled, no trap installed at the new bathroom sink!

Chris - you got it :).  Just run a little water.

Debbie - that's right.  Those basement toilets never get much use.  

Ginny - such an easy fix.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Scott S - Ok, you got a belly laugh out of me with that comment!

Joy - if you look in the toilets and you see pink stuff, you know it's already been taken care of.

Beth - next stop: Home Depot for some RV Antifreeze.

Michael - thanks.

Harry - hopefully that's what you're smelling :).  If that ain't it, it might be a tougher solution.


Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Richie - as always, thanks.  Much appreciated.

Chris and Dick - grab some antifreeze and it will no longer be a regular maintenance thing.

Vanessa - I've talked to so many homeowners that have lived with these odors and never figured them out.  It's always an "aha" moment for them when I explain the odor.

Ashley - You're right, I've smelled some pretty nasty smelling well water before.

Ann - I never thought of cooking oil.  Thanks for the tip!

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Margaret - if you use the shower twice a day, antifreeze isn't going to help.  Try looking down the drain with a flashlight; can you see water in there?  If not, you might not have a trap.  If that's the case, you'll be looking at a more extensive (and expensive) repair.

Charles - I think it must have been time for that plumber to retire ;)

Andrew - no thanks :)

Sandy - If you ever find pink stuff in the toilets at bank owned properties... you'll remember this.

Jay -  well, yeah... but that just goes without saying, right?  I mean, duct tape will fix anything :)

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Donald - I'm familiar with those trap primers, but I've never actually seen one in the wild.  Have you?

Erica - me too!

Myrl - thanks.

Evelyn - glad to help, thanks!

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Common sense says make sure there is water in the toilet or drain. Same situation if a disposal hasn't been run in a while.

Posted by Bill Reddington, Destin Florida Real Estate (Re/max Southern Realty) over 6 years ago

Like Don said, a trap primer. I have recommend them, but haven't seen one "in the wild". 

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 6 years ago

This is one of the things I also tell my clients.  If it has not been used as of late, dump some water in it. The Anti-freeze is a great idea.

Posted by William Feela, Realtor, Whispering Pines Realty 651-674-5999 No. (WHISPERING PINES REALTY) over 6 years ago