Causing sewer blockage?

Well, I spent a summer working on sewers, and typically a blockage for a town would be nigh on impossible short of collapsing line. The only other possibility I can think of that occurs with any frequency is from flooding/power outages. If a power outage happens and a lift station pump can't run(the backup generator doesn't work, or some sort of mechanical failure happens), then that will ABSOLUFREAKINGLUTELY cause a flood. Basically any house that is at or below that pump is going to get a backlog of sewage as it gradually fills the pipes back up.

If you want to plug up a building, or screw up a septic tank I can give you some easy ideas.

The simplest method is to simply flush tampons/condoms/paper towels/stuff that shouldn't be in the toilet down the shitter. The grinder pump in a septic tank that pumps into a sewer(for pressurized sewers, which are common in really hilly areas) tend to get choked by condoms because they don't grind, and they just get stuck. Tampons on the other hand tend to hang up in sewer pipes within buildings, and then that causes stuff to snag on them. It's not uncommon for female dorms to have issues because a ton of chicks flush their tampons down the toilet and they get stuck.

It's not impossible to block a sewer, I used to work for the wastewater department of my city (now I work on the clean water side, the smell's much better ). Crews will sometimes have to block an area of pipe if they have to work on it. There are devices sold to do just that. They're called plugs. Some are just big stoppers, some are like inflatable bags, depending on the size of pipe that has to be blocked. Also depending on where the sewer plant is there are probably lift stations. These are basically big tanks that receive the waste that is gravity fed and lifts it to a higher pipe. if there are a lot of hills in the area there would have to be several of these. Shutting down the pumps in a lift station would eventually back up all the pipes leading into it.

Keep in mind that unlike drinking water, the pipes for wastewater are rarely full, unless it is a pipe directly from a lift station, so it will take a while, depending on the size of pipe and the flow in the sewers, for the waste to build up behind whatever she uses to block the pipes.

One thing that we constantly struggled with when I worked in that department, and this is true of ANY city with restaurants. GREASE. It looks so innocuous when you pour it down a drain but it hardens in the sewer pipes and builds up, and builds up until there is a blockage.

Capes&Corsets said:

Thank you, Dommo! Hmm I guessed it would be impossible...however, you mentioned flooding and it got me thinking. Is there a way of causing a flood in a certain area that would create a mass flood? Apologies for my terrible explanation here

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Got a nearby flood-control or power-generating dam that you don't mind blowing up?

If you just want a flood, the Duncan's idea is best.

Capes&Corsets said:

Duncan, you mentioned a flood-conrtrol dam - stupid question, but do a lot of towns have this? My fictional town is small, tough not far from a big city and there is a river that surrounds it. The character wishes to cause a bit of havoc (though nothing huge) and this is a quick way.

Would a small town be likely to have this kind of set-up with regards to the sewer system? And could, as Duncan said, blowing something up, do a lot of damage?

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If there is a river around the town, then there almost certainly are some dams or other flood control structures. It's too bad that it isn't an old mill town with a river through it and a power station on the old dam in the middle of town. The old dam supplied power to mills in the 1800's, but they have all closed down or converted to electric power.

Anyway, nearly all small dams have a gate that allows the retention pond to be drained. These are usually manually controlled and are readily accessible. Draining the pond would create a flood, if the old riverbed had been reused. Look also for flood control reserviors in the hills above the town.

By plugging I meant for a typical average joe. We had the equipment to plug up the sewers, but I'm saying for something easily achievable a power outage would be easiest, or simply sabotaging the emergency generator.

Flooding is a big problem when you've got big storms coming through the area, and a few inches of rain, having a lift station fail will cause some serious mayhem in low lying areas.

Our street was blocked (about ten houses) when someone had somehow put a t-shirt down their toilet.

Capes&Corsets said:

Argh! I'm currently rewriting my novel and have added in a few more things. Without going into much detail, my character has to block the town sewer.

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A weather balloon, or other large inflatable object would work as long as she protects the upstream side against ripping.

You can buy the balloons online or through a scientific education supply catalog.

I read about this idea to plug a house/building's sewer pipe, but I don't know if this could be made to work on a main line:

Get a large sponge which is clearly big enough that it would never pass through the line, squeeze it into a ball as tight as you can and wrap it in twine, then soak it in a starch/water solution for a few hours.

Take it out and let it dry completely, then take off the twine and you should be left with something hard and small enough to initially flush down the pipe, but will completely plug everything up as soon as it soaks up enough water.

I haven't tried this myself, but I've filed it away in the back of my mind should such an emergency turn up someday.