Been leasing a great condo for years and several months ago, the hot water valve broke in the laundry room closet's valve box, which is located in wall just above the washer. The side by side washer (and dryer) were temporarily removed from the laundry closet for about 2 months during floor & drywall repairs. So the washer and its drain line weren't in use for that entire time period. Throughout that time, there was a persistent, but intermittent foul odor recurring from the laundry closet. Contractors and property manager etc. attributed the smell to the "dried out, unused washer drain." That seemed to possibly make sense, but the washer's now been re-installed and back in service for over 8 weeks using the drain line and the intermittent, but persistent foul smell continues and is typically strongest near the valve box's drain. [Independent inspections and testing have eliminated mold as potential odor cause.]

BTW, Zero prior problem or smells existed during all previous years I've been using the appliances in the laundry room.) The owner's plumber recently claimed it can't be a sewer line issue or the smell would be constant and essentially dismissed taking action.

I think he's wrong and it's far more likely there's some malfunction in the trap for the washing machine's drain line that's not providing its proper vapor barrier. Hence I'm smelling intermittently noticable stinky fumes wafting up into the laundry closet and adjacent rooms. But what's the best approach to pin down the actual odor cause?

What action/s should I be asking my 2nd opinion plumber to do in order to accurately diagnose and fix the foul smell issue? Would putting a plumbing camera down the drain to scope it indicate if the trap was functioning properly to provide a water barrier to the sewer gasses? Any other suggestions or ideas for effectively identifying and fixing the cause of this recurring foul odor would be greatly appreciated. Thank you.



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If the washing machine stand pipe in the washer box has water in it it is most likely not the trap

If the person in the unit below you doesn’t complain that it’s raining in the unit when you use the washer it’s most likely not the piping

If you have no indication of sewer flies it’s probably not the piping

It may just be the washer itself

Take the washer drain hose out of the drain. Plug the drain completely: multiple plastic bags with rubber bands, or a rubber cap with a clamp if you have one.

Then close the room for a day. If you come back and the smell is there, the smell is likely coming from the washer itself, and not from the drain. Front load washers are infamous for this.

Unless there is a floor drain in the room somewhere...

Thanks for responding. This noxious odor first began immediately AFTER the old washer was junked and there were no connected appliances in the laundry closet for 2 full months. This smell problem is strongest near the valve box drain which was "uncapped" during all those two months.

Then, a brand new TOP loader was installed which & has been used for the most recent 7 weeks; it has all new water hoses and new plastic drain line for washer hookups.

So the problem smell did not go away once the valve box drain in the laundry closet wall was regularly draining new gray water into the trap from various loads of laundry, etc. Also No leaks and all moisture meter readings on all walls are in normal range.

So the smell is not from the new washer. There remains a persistent, intermittent foul smell localized near the valve box drain that wafts into adjacent hallway and rooms when its at its strongest.

So any further suggestions for potential fixes to address the smell's cause would be very welcome. Scope the drain pipe? And is the smell likely from a flaw in the vapor barrier of the p-trap in laundry drain pipe? BTW, building complex built 2006, so relatively new.

? failed 'hidden' AAV ?

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Less expensive test -

Do like Dave said and plug everything off. Can do one at a time .....process of elimination.

Also check for failed AAV as per Bernabeu.

More expensive - peppermint test, camera inspection...

Finding smells is sometimes like finding a needle in a haystack.

Good luck.

I was also thinking of a failed AAV behind wall that is not accessible.

I would also do a few tests as been suggested by others. If the laundry stand pipe is in a drain box then you cannot cap over or bag over it, just take a trash bag stuff some papers in it until it is larger than the size of that stand pipe diameter, stuff it into the stand pipe opening to block it. To see if the odor disappear. A failed AAV or a dead rodent inside the wall cavity will still exhibit the odor.

Is the odor stronger than the washer drain is discharging or no difference?

What happens if you take the hot water hose going to the back of the washer, unscrew it, take that end and run it into the stand pipe drain box and turn on the hot side valve? What happens? Do you get a stronger odor or not?

Do you have a shop vac? Take a shop vac and switch the hose from the suction side to the outlet side to get it to blow. Stick that hose into the stand pipe opening. Wrap the hose with a wet rag to seal the connection as much as you can, turn vac on and get the vac to blow air into the pipe, do you smell anything coming out of the wall cavity?

Thanks.



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Thanks, it has been a blasted needle in a haystack to pin down source of this smell.

I'm going to next try DaveMill's test idea of blocking off the drain opening for 24 hours.

Note as a leaseholder (in a condo building), I can't do or authorize a smoke test or a peppermint test. My goal here now is strictly diagnostic, to obtain concrete data that narrows down the smell's cause to convince the landlords to finally fully address & repair the problem.

So my next step (after doing a drain-block-off test) would have to be a mini-camera scoping of the washer's drain.

Any thoughts on how relatively useful such a camera scoping of the drain line is for revealing a hidden AAV issue and/or some other issue in the p-trap's functioning or the rest of the drain pipe?

Using a DIY borescope that is connected via a mini USB to your smart phone will have virtually zero chance of it making past the p-trap.



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Not DIY on the scoping. I plan to hire a plumbing contractor w/the specialty mini-camera equipment.

Would a plumbing company's specialty mini-camera equipment be able to get visuals past the p-trap? And/or determine if there's an AAV problem and/or some other issue with the trap or the rest of the pipe?