Home & Garden

Wasp activity in washroom vent outside

  • Last Updated:
  • Aug 15th, 2021 4:52 pm
[OP]
Deal Fanatic
Sep 16, 2013
6949 posts
4679 upvotes
SW ON

Wasp activity in washroom vent outside

We noticed increased wasp activity in the decorative grapevine. Usually it's a sign of a nest nearby as I had to destroy their nests almost every year. The nests were on trees, compost bin, attached to the house. But this time it's worse. There is an activity in the vent from a forced washroom ventilation. They get in and out. Seems like they are building a nest inside. No sign of them inside the house... yet.

Does anyone have any suggestions? For wasp nests on trees and the house I used Raid Max Wasp & Hornet foam spray at dawn. This time if there is a nest it's inside the vent. I can reach it with a ladder but I need to unscrew two screws to remove the vent, then I need to look inside and see where to spray. I will be attacked while doing this. When I discovered the first nest in the compost bin years ago while mowing lawn I was bitten by 5 wasps while running away from the place (the lawnmower exhaust angered them). So, I have a pretty bad experience and don't want to repeat it. Nests on trees were easy to destroy.

Should I call an exterminator? Any idea how much they charge? I wonder how they work. Special PPE?
15 replies
Jr. Member
Nov 15, 2009
134 posts
18 upvotes
Saskatoon
I think you should do this kind of job at night, like after 10pm when they are not active and wearing a big long coat with hat and mask, even with glasses to protect yourself. I recently bought a product called one shot Wasp & Hornet Killer, there is a tube to extend the spray head, so it can reach further in the hole. My house wasp also hiding under a wooden deck which I could not move away, so I just spray into the hole where I saw them fly in, the next morning I barely see wasp flying, just one or two, so I repeat the process again the second day at night, and now they seemed to be disappeared, but I am going to do it again to make sure they won't come back.
Deal Fanatic
Jul 7, 2017
8390 posts
4083 upvotes
SW corner of the cou…
Maybe try a boric acid (or BORAX solution) mist into the vent (I'd avoid insecticides that close to the house). That is toxic to insects. Otherwise leave it alone until the first or second frosts and then remove the nest (should be abandoned by then, and remnant wasps dead).
I smile when I see container ships sailing past my house laden with stuff made in China
Deal Fanatic
Jul 7, 2017
8390 posts
4083 upvotes
SW corner of the cou…
amybear wrote: I think you should do this kind of job at night,
FWIW, wasps can;t see red light so if you use a red light filter, they are blind.
I smile when I see container ships sailing past my house laden with stuff made in China
Deal Addict
Jun 14, 2008
4142 posts
2925 upvotes
Montreal
I had a wasp nest inside my air exchange intake duct once. What I did was wait till night, remove the external grill, then removed the duct from air exchanger and blew through it with the most powerful leafblower I have. Found the nest on the grass below and sprayed the nest with bug spray, done.
Deal Guru
Feb 9, 2006
12918 posts
7676 upvotes
Brampton
jzmtl wrote: I had a wasp nest inside my air exchange intake duct once. What I did was wait till night, remove the external grill, then removed the duct from air exchanger and blew through it with the most powerful leafblower I have. Found the nest on the grass below and sprayed the nest with bug spray, done.
That reminds me of a video I saw where a guy used a shopvac to suck them out inside the shopvac IIRC was some soapy water so they all drowned after some time.
[OP]
Deal Fanatic
Sep 16, 2013
6949 posts
4679 upvotes
SW ON
thriftshopper wrote: Maybe try a boric acid (or BORAX solution) mist into the vent (I'd avoid insecticides that close to the house). That is toxic to insects. Otherwise leave it alone until the first or second frosts and then remove the nest (should be abandoned by then, and remnant wasps dead).
Since it's inside the wall I am not sure it will ever get frosty in there. And I am not sure if I can inside the wall to remove the nest. I think I should do something now to prevent them from building a large nest.

Borax, sodium tetraborate is not really toxic to anybody. It dehydrates insects but it doesn't kill them on the spot, it takes time. It's used to kill ant nests but one needs to feed them a LOT of it, and they need to bring it inside the nest and feed the others. Only then they will slowly die by dehydration, not able to quickly find source of water to drink. It won't work on wasps.
[OP]
Deal Fanatic
Sep 16, 2013
6949 posts
4679 upvotes
SW ON
jzmtl wrote: I had a wasp nest inside my air exchange intake duct once. What I did was wait till night, remove the external grill, then removed the duct from air exchanger and blew through it with the most powerful leafblower I have. Found the nest on the grass below and sprayed the nest with bug spray, done.
Unfortunately, mine seem to inside the wall. I can't blow them anywhere.
[OP]
Deal Fanatic
Sep 16, 2013
6949 posts
4679 upvotes
SW ON
thriftshopper wrote: FWIW, wasps can;t see red light so if you use a red light filter, they are blind.
The idea to do it at night is because they all go home into the nest before sunset and sleep there the whole night. During the day they roam around. If a nest is destroyed at day time there will be a lot of wasps left that won't be able to find the nest. They will be very aggressive and stay in the area until they die out. They are territorial. Wasp nests should only be destroyed at night time. It's OK to use a flashlight to locate a nest at night. They are all inside anyway. I used to do it at dawn when it's slightly bright. It was hard to wake at the right time, though.
[OP]
Deal Fanatic
Sep 16, 2013
6949 posts
4679 upvotes
SW ON
Unfortunately, the problem is worse than I thought. I looked with the binoculars and it looks like wasps are entering in a hole between the vent pipe and the wall. I think they are getting into the wall and building a nest there. I can foam-spray the entrance with insecticide but I don't think I will kill the nest. It might be deeper in the wall. Who knows how far they travel in the wall. Does anyone think if I foam-spray with the wasp insecticide the entrance hole it will help? Whoever is inside the nest they might just wait until the insecticide is washed away, evaporates and continue to use the nest. If I seal the entrance hole they might find another or worse find a hole into the house. I will call an exterminator. Meanwhile, any ideas?
Deal Fanatic
Feb 4, 2010
6598 posts
6074 upvotes
I would definitely hire a professional....if this happens every year you probably have a pretty big colony. You don't want to be swarmed by them...it's so incredibly painful.

Deal Addict
Jun 14, 2008
4142 posts
2925 upvotes
Montreal
Hmm that's a bummer, the thing is you don't actually know how deep is the next and if you just spray in the hole, will it even reach the nest.

If it was me, I'd be tempted to spray a bunch of liquid form permethrin based insecticide (not the foamy wasp specific type) into the hole, seal it with duct tape, wait a few days and see if they die off, or there are other entrances.
Deal Guru
User avatar
Nov 18, 2005
11667 posts
3170 upvotes
Kingston
jzmtl wrote: I had a wasp nest inside my air exchange intake duct once. What I did was wait till night, remove the external grill, then removed the duct from air exchanger and blew through it with the most powerful leafblower I have. Found the nest on the grass below and sprayed the nest with bug spray, done.
I had similar but by the time i found them their nest was a foot long in the duct. Had to replace the duct (after I totally soaked the nest with wasp killer).
tebore wrote: That reminds me of a video I saw where a guy used a shopvac to suck them out inside the shopvac IIRC was some soapy water so they all drowned after some time.
Did that too in another location the infiltrated the house. Worked well. The soap in the water is just to break the surface of the water. Got them going out and in. Had it running for about 8 hours.
Deal Guru
User avatar
Nov 18, 2005
11667 posts
3170 upvotes
Kingston
alpovs wrote: Unfortunately, the problem is worse than I thought. I looked with the binoculars and it looks like wasps are entering in a hole between the vent pipe and the wall. I think they are getting into the wall and building a nest there. I can foam-spray the entrance with insecticide but I don't think I will kill the nest. It might be deeper in the wall. Who knows how far they travel in the wall. Does anyone think if I foam-spray with the wasp insecticide the entrance hole it will help? Whoever is inside the nest they might just wait until the insecticide is washed away, evaporates and continue to use the nest. If I seal the entrance hole they might find another or worse find a hole into the house. I will call an exterminator. Meanwhile, any ideas?
Wherever they are you should be able to hear them. Bang on the wall or vent and that will get them a little excited and make a lot of noise. If they are in the vent, seal off the inside before you do anything so they don't try to exit into your house.

DON'T seal off the outside. If you do they will try to chew through and also be trying to chew through to find another exit point (like into your house). They will chew through almost anything.

If you can hook up a shop vac with the hose end at the entrance that can be very effective. Use the crevice tool for maximum suction. You'll have to leave it running for hours.

The spray foam will help but will require repeated applications. Time will tell if the vacuum + foam works. Has for me but each situation is unique.

As others have said, whatever you do, do it at night.

For next year... after a couple of years of wasp problems I put a bunch (5) fake wasp nests around the house and haven't had problems since.
Deal Guru
Feb 9, 2006
12918 posts
7676 upvotes
Brampton
jzmtl wrote: Matthias Wandel? Might be somebody else though I don't think he used soapy water.

https://www.youtube.com/results?search_ ... andel+wasp
Maybe. I honestly don't remember.

As mentioned by another member the soap in the water is to break surface tension so the is a higher chance they hit the water and go right thru and then they're soaked and can't fly or grip anything and drowned overtime.

Top