# Troubleshooting Brainteaser



## dustie bootz (Feb 18, 2011)

We all pride ourselves with our troubleshooting expertise. I thought I might share one of my favorites with you guys.

Problem; Everytime the heat is turned on in the morning one office space gets innundated with live black gnats. It is a doctors office and is rather unsightly. Live gnats are in a SINGLE room space in 8 room office below and gnats come out of sink drain above in the public restroom.

Structure; 8 unit multi-use building, 2 storys, newer construction 1995 and up. Contains doctors offices, retail spaces, salons, massage-therapy, chairopractors, etc.

Ceiling ares; Truss above, open plenum below, acoustic tiles on grid. Heat is supplied with forced air heat pumps. There are only dead fies in the plenum and very few. Heat pumps have recently been serviced and there are 3 that supply this space.

There are no rats or dead animals and the building and plenum are 99% energy sealed.

Where are the gnats coming from and how do I get rid of them?

Any other questions?

This will be fun. :thumbup:


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## 504Plumber (Jan 26, 2011)

dustie bootz said:


> We all pride ourselves with our troubleshooting expertise. I thought I might share one of my favorites with you guys.
> 
> Problem; Everytime the heat is turned on in the morning one office space gets innundated with live black gnats. It is a doctors office and is rather unsightly. Live gnats are in a SINGLE room space in 8 room office below and gnats come out of sink drain above in the public restroom.
> 
> ...


Something not vented right and sucking the water out of sink p-trap?


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## PlungerJockey (Feb 19, 2010)

There is a break or opening in the building drain somewhere.


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## vinpadalino (Aug 27, 2010)

Install a big trap!


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## Lifer (Nov 23, 2010)

vinpadalino said:


> Install a big trap!


 

LOL do you mean a BUG trap ...

Lifer...


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## Widdershins (Feb 5, 2011)

I'd look for an unused (dried out) indirect drain, floor drain or floor sink in a mechanical room or closet.


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## LEAD INGOT (Jul 15, 2009)

Is there a fresh air exchanger?


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## 6th Density (Nov 29, 2010)

Just throwing it out there...

...is there a vtr terminating too close to a fresh air intake?


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## Bill (Jun 17, 2008)

Maybe a floor trap with no trap primer


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## Redwood (Sep 8, 2008)

Those are sewer flies AKA filter flies.
The trap on the HVAC drain is dried out wherever it may be and thats where they are coming from.

Not much of a brain teaser...

How long did it take you to figure it out? :laughing:


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## stillaround (Mar 11, 2009)

How about a toilet in bad need of a reset....in case Red is wrong..( you know he can be wrong.....he's not always right) I dont remember last time he was but I dont pride myself in a steel trap memory either.


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## Redwood (Sep 8, 2008)

Yea it could be that too Stillaround... :thumbup:

If they came from the toilet they might have taken up residence in the HVAC in a humidifier or something so that every time it turns on they come blowing out.

They can be hard to get rid of once you get them on the wrong side of the trap...

http://www.ces.ncsu.edu/depts/ent/notes/Urban/drainfly.htm


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## waldrop (Dec 18, 2009)

We have same problem at our family pond build in 1939 ,my older uncles used to tell me to cut a hole in pants near butt that will fix gnat problem:thumbup:


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## 6th Density (Nov 29, 2010)

Redwood said:


> Those are sewer flies AKA filter flies.
> The trap on the HVAC drain is dried out wherever it may be and thats where they are coming from.
> 
> Not much of a brain teaser...
> ...


I hear ya on that Redwood, but if I'm correct on OP's assessment, the bottom floor has peter flies and the same adjacent top floor "public" restroom lav. has peter flies coming out the trap. Why would a "public" restroom lav. trap dry up on an "supposedly" occupied building? What's creating the negative pressure?


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## Redwood (Sep 8, 2008)

6th Density said:


> I hear ya on that Redwood, but if I'm correct on OP's assessment, the bottom floor has peter flies and the same adjacent top floor "public" restroom lav. has peter flies coming out the trap. Why would a "public" restroom lav. trap dry up on an "supposedly" occupied building? What's creating the negative pressure?


The trap in the lav doesn't have to be dried out, they can come in another way initially but it sure can be a great breeding ground for them...

The eggs look like gelatin in the drain...


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## 504Plumber (Jan 26, 2011)

Redwood said:


> The trap in the lav doesn't have to be dried out, they can come in another way initially but it sure can be a great breeding ground for them...
> 
> The eggs look like gelatin in the drain...


I read that link you had, always wondered why crap in a sewer always had little worm looking guys in it, never put 2 and 2 together.


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## Redwood (Sep 8, 2008)

504Plumber said:


> I read that link you had, always wondered why crap in a sewer always had little worm looking guys in it, never put 2 and 2 together.


That might be tubifex worms...

Another sewer dweller...


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## 6th Density (Nov 29, 2010)

Redwood said:


> The trap in the lav doesn't have to be dried out, they can come in another way initially but it sure can be a great breeding ground for them...
> 
> The eggs look like gelatin in the drain...


Cool, I didn't know that. Makes me wonder the potential of what could grow in that damp overflow drain cavity of a lav or tub.


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## 504Plumber (Jan 26, 2011)

Redwood said:


> That might be tubifex worms...
> 
> Another sewer dweller...


Whatever they are, don't like em, mucho yucky.


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## smoldrn (Oct 4, 2010)

I ran into those in a house the owners only visit 1-2 times a year. The bug man had sprayed everywhere, but they still had gnats. Poured bleach in every trap & overflow, let set for an hour, then flushed well with hot water, no more bugs. Their eggs hatch every couple of days, hence the bleach. 
Solved the problem.


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## dustie bootz (Feb 18, 2011)

Redwood said:


> Those are sewer flies AKA filter flies.
> The trap on the HVAC drain is dried out wherever it may be and thats where they are coming from.
> 
> Not much of a brain teaser...
> ...


 
You gessed it, I was the third serviceman to take a crack at it and it took me about an hour to figure it out. Bleached the lav and floor drain too.
That was fun. :thumbsup:


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## 6th Density (Nov 29, 2010)

Well I was thrown off by a few things, but fun none the less.

Why would they only show up when the heat was turned on?
...Made me think they were coming out of the grills.

What are the odds of the the 2 units, top and bottom, having an issue? 
...1 - being the dry floor drain on bottom floor with no complaints of sewer gas. 
...2 - somehow these peter flies smelt their way to the top floor water supply and started laying eggs in the lav. p-trap. 
Or can peter fly larvae swim? It just made me think something was causing the trap seals to break.:thumbup:


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## PLUMBER_BILL (Oct 23, 2009)

6th Density said:


> Well I was thrown off by a few things, but fun none the less.
> 
> Why would they only show up when the heat was turned on?
> ...Made me think they were coming out of the grills.
> ...


*Reading these answers. A lot was for dried up floor drains. One trick for a non primered trap was to pour oil down to keep the seal from evoporating. *
*This is fine but ... food oil will draw ants, gnats, bugs and all other creatures. Mineral oil will not draw these things. *


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