I have an issue with a retail store my wife and I lease. We completed a modest interior buildout and turned on the AC for the first time about 8 weeks ago... which was about 2 months after we took the lease. We soon noticed a rotten egg smell. We shut off the AC and the smell lingered but eventually went away. The problem has been getting worse and worse.

The management company was not quick to respond but eventually came out and had the entire AC unit cleaned out, filters replaced, etc. The technician said the AC was quite dirty... BUT... only a day later the smell returned.

We called the management company again and after weeks of this smell getting worse, they had a plumbing company come out and snake the lines, etc. After this - things seemed to get even WORSE!

After some basic research, we are now very certain that this smell is sewer gas. The AC unit (I think it is a swamp cooler type) is about 15' away from the sewer vent on the roof. The management company put a special plastic cap / filter on the top... but it is obviously not helping. The sewer vent is about 12" off the roof line and our AC unit is about 36" above this... but it is a considerable distance away.

Here is the strange part... our space is about 25' from a set of bathrooms and the sewer vent stack. The space next to ours (and closer to the bathrooms) experiences very little smell. Their unit is closer to the sewer vent. We've inquired with other tenants and they've said that low levels of this smell have been noticed from time to time over a 3 year period... but presently... it is WAY worse than ever... we are feeling like some people think it's something we've done!!

I'm curious why this might be getting worse after a visit from a plumber... why the problem is VERY bad for us and not that bad at all for our neighbors (assuming that there is some issue with the sewer gas getting sucked into our AC system and theirs is closer to the source!) and why the smell doesn't seem to appear at all if our AC system is off.. and the AC recently having been cleaned.

We also did a quick test today by keeping the AC off... seeing if there was any smell... (there wasn't) and then turning the AC on and flushing the toilets multiple times and running the sink water in the restrooms for a minute or two. The smell was terrible. It does smell in the restrooms but the smell is worse in our store!

There is one other bit of info... the management company capped a slop sink that is in our space. The sink is about 30' away from any other plumbing fixture, has it's own vent line and is capped. I am wondering if it could be part of the problem if it is somehow connected on the waste side to an issue over at the toilets... and / or if any of our construction even slightly tapped into the vent line in wall for this sink? I was very careful to only hit studs and our there is only one small blackboard we installed that would even be close to the vicinity of the vent pipe... but it's a plumbing fixture.. and we're smelling sewer gas... so I figured it could be part of the problem... but I doubt it.

Lastly... today when we flushed the toilets... we noticed that the water pressure seemed very poor and there were bubbles in the toilet water when flushed...

Any thoughts are greatly appreciated. We are trying to get to the bottom of this so we can operate our business!!

I have an issue with a retail store my wife and I lease. We completed a modest interior buildout and turned on the AC for the first time about 8 weeks ago...which was about 2 months after we took the lease. We soon noticed a rotten egg smell. We shut off the AC and the smell lingered but eventually went away. The problem has been getting worse and worse.

The management company was not quick to respond but eventually came out and had the entire AC unit cleaned out, filters replaced, etc. The technician said the AC was quite dirty...BUT...only a day later the smell returned.

We called the management company again and after weeks of this smell getting worse, they had a plumbing company come out and snake the lines, etc. After this - things seemed to get even WORSE!

After some basic research, we are now very certain that this smell is sewer gas. The AC unit (I think it is a swamp cooler type) is about 15' away from the sewer vent on the roof. The management company put a special plastic cap / filter on the top...but it is obviously not helping. The sewer vent is about 12" off the roof line and our AC unit is about 36" above this...but it is a considerable distance away.

Here is the strange part....our space is about 25' from a set of bathrooms and the sewer vent stack. The space next to ours (and closer to the bathrooms) experiences very little smell. Their unit is closer to the sewer vent. We've inquired with other tenants and they've said that low levels of this smell have been noticed from time to time over a 3 year period....but presently...it is WAY worse than ever....we are feeling like some people think it's something we've done!!!

I'm curious why this might be getting worse after a visit from a plumber....why the problem is VERY bad for us and not that bad at all for our neighbors (assuming that there is some issue with the sewer gas getting sucked into our AC system and theirs is closer to the source!) and why the smell doesn't seem to appear at all if our AC system is off..and the AC recently having been cleaned.

We also did a quick test today by keeping the AC off....seeing if there was any smell....(there wasn't) and then turning the AC on and flushing the toilets multiple times and running the sink water in the restrooms for a minute or two. The smell was terrible. It does smell in the restrooms but the smell is worse in our store!

There is one other bit of info....the management company capped a slop sink that is in our space. The sink is about 30' away from any other plumbing fixture, has it's own vent line and is capped. I am wondering if it could be part of the problem if it is somehow connected on the waste side to an issue over at the toilets......and / or if any of our construction even slightly tapped into the vent line in wall for this sink? I was very careful to only hit studs and our there is only one small blackboard we installed that would even be close to the vacinity of the vent pipe...but it's a plumbing fixture..and we're smelling sewer gas...so I figured it could be part of the problem...but I doubt it.

Lastly...today when we flushed the toilets...we noticed that the water pressure seemed very poor and there were bubbles in the toilet water when flushed...

Any thoughts are greatly appreciated. We are trying to get to the bottom of this so we can operate our business!!!
I am not an AC guy, but I think I can help. There are 3 parts to an AC unit. The inside part, called the air handler. The outside part which is which has the compressor and the drip line that takes away the water from the moisture in the air handler. My guess is that by clogging up the pipe going to the sink has caused the air vent to also be clogged for the toilets. In a house you have air vents to for smell and to keep water flowing in the toilet. For example, think of a straw and a drink. If you put your finger over the top and capture the liquid it will stay in the straw. If you then release the your finger the liquid will fall. I think you have a clog on the vent side or management has plugged up a vent needed for even water flow for the toilets. To answer you question on AC, I think that all these pipes meet some ware in the wall and that standing water is now sitting in the air handler area causing the smell to go into the inside unit across the coils. My suggestion would be to let management know that you want the drip line checked and separate from any other drain connection or line. I think this would fix the ac problem. As far as the toilet goes, there is an exhaust pipe that is probably clogged that is making the toilets bubble and could back up. This pipe is usually on the roof and can be cleaned by stuffing a garden hose down the pipe to break the sludge up, letting the toilets flush.

Hope this helps!