What would cause a geyser of sewage from toilets and sinks?

[roykirk70]

This is more for my own knowledge and curiosity. I manage a single floor office in a building that was built in the early 1970s. Recently we had a toilet plug up and the sinks stopped draining. We called in a well known and highly regarded plumber to take a look at it. He initially had a trouble finding any problem, but eventually snaked the sewage drain line under the building and found a clog halfway between the building and the street (where it connects to the city sewer line). The moment he cleared the clog, we got a geyser of raw sewage from every toilet and sink in the office. As you can imagine, it's a huge mess but at least we have a good insurance that's taking care of the cleanup.

Anyway, the plumber said he's never seen anything like this after 20 years in the business and he's not sure what could have caused it. We spoke to the city and they claim nothing on their end could have caused such an event. Plumber thinks the only way it could have happened is if a city pump kicked on or something at the moment the clog was cleared. The city denies that is possible, perhaps due to fears of liability? Anyone have thoughts or theories on this?

 

[FishScreener]

Unless you have a second floor, the energy to do it came from somewhere and I would suspect the sewer main as the most probable cause.

 

[roykirk70]

Yeah, there's no second floor. It was just bizarre. The pressurized discharge lasted a good 20 seconds. We had an inch of sewage in all the bathrooms and the breakroom (where there was a sink located). An added curiosity is that no other businesses on our block had any problems.

 

[Stout Mechanical]

What did they clear the drain with?

 

[mark3885]

Sounds like too much Chili or tacos in the diet! Sorry , couldn’t resist. Pressure from the sewage system obviously, was the sewage dept doing any high pressure sewer jet cleaning?

 

[Geofd]

i saw something like that at work but there was no clog and only the basement toilet was affected that day in the street the was a contractor working for the city clearing a stoppage in their main...they were using a water jet, they had 5000 lbs presure on on it so ,when they started jetting the water had no place to go exept into our buiding
we were lucky it was only clear water,and it only ruined some ceiling tiles , we went outside made asked them to turn
dowm the pressure ,in the mean time not trusting the we actually wrapped the toilet in plastic like you would a plalet
ready for shipping

 

[roykirk70]

What did they clear the drain with?

Some sort of wire/cable snake looking thing.

 

[roykirk70]

Sounds like too much Chili or tacos in the diet! Sorry , couldn’t resist. Pressure from the sewage system obviously, was the sewage dept doing any high pressure sewer jet cleaning?

Not that they would admit to. We didn’t see any sewer crews working nearby.