Oh rats

The other night I saw a rat in my room. I gasped so loud I woke up.

Sometimes rats turn up for real and sometimes they turn up in the lavvy (City, Fältbiologen). I realised there are many things about sewers I usually don't think about. Incoming water pipes are under pressure, so they are filled with water, but sewers are fed by occasional bursts from showers, toilets, washing machines and such; the pipes in a building are then empty most of the time. I suspect even the larger pipes under the streets must be mostly empty, so that there are margins for everybody showering at the same time in the morning and so on. But, are all solids in the sewer water properly flushed away then? I guess they have to be, or the sewers would be clogged more often. So, there is enough water flowing through the system to keep everything moving. Rats then? They scamper around in the pipes, on the lookout for food I presume, or perhaps there are rat spelunkers that poke around just to see what's around the next bend in the pipe and climb up several stories in the house pipes. A water lock? Well, there's light coming through, so maybe the water's not a lot. Are these very desperate or very confident rats that take the plunge and poke their nose up someone's toilet bowl? And imagine all the rats, cautiously climbing up pipes like long-tailed Indiana Joneses and suddenly the defences of the ancient temple are triggered and a bolus of water, toilet paper and crap comes at them from five stories up. Does one survive that? Just hang on by the claws in the pipe while it passes or ride along, trying to get a breath of stinking air every now and then? Is it like white-water rafting or just sheer terror for the afflicted rat? So many questions, so difficult to find out.