rats in the toilet

Evidently there are rats coming into people's houses through their toilets. This is happening in the city where I live. We are being advised to keep our toilet seats down. This "epidemic" for lack of a better word, is ticking me off. The reason for my ire is rather personal, but I'm willing to share it in the hope that it will help someone.

For years I was nervous about using the toilet. You see, I had heard about giant snakes making their way up from the sewer system through the plumbing pipes into peoples' homes through their toilets. Snakes that had been flushed when they were smaller and the owners realized that they'd inadvertantly purchased an anaconda instead of a ... garter snake? (I don't know what they thought they'd be buying. I don't know the names of non-venomous small snakes.) So, when the urge would strike to use the facilities, I would always carefully peer into the toilet bowl and scan for reptilian intruders. And at night, I would have to turn on the light to see the toilet and floor clearly - in case the snake had already slithered out of the comode and was coiled in the shadows behind the tank. This fear was something I lived with. Not a huge deal. Not something I talked about.
Let me add here that it did not help my state of mind when I would have my snake dreams: dreams of snakes, warm heavy snakes with dry scales, chasing me or lurking in my bed (ok, dial back the Freudian analysis people - sometimes a snake is just a snake). Dreams so real that I would wake up and know that if I stretched my toes I would touch the snake underneath my duvet. So I'd carefully withdraw my feet and scooch up onto my pillow and turn on the light, before whipping off the covers to make sure I was alone.
When I began living with my soon to be husband, he questioned me about my pre-toilet precautions. So I told him. He assured me that toilets didn't work that way. He told me, with the authority of someone whose brother is a plumber, that there is a flap of some kind that prevents things from making their way up from the pipes. He said that the flap only flaps one way. And I believed him!
Slowly I let go of my snake invasion visions.
Many years passed.
I felt proud that I could relieve my bladder in the middle of the night without turning on the light, secure in the knowledge that the flap only flapped one way and there was no way a snake, a huge sewer snake with abandonment issues, would raise it's head from the coil of it's slumber in my toilet bowl.
Then, I hear from some people that rats are coming up through the toilets!!
How come rats can do it and snakes can't? Has it all been a lie? Have I just been supremely lucky to have avoided a reptilian standoff thus far?!

Can I trust my husband?

So, yeah. I'm pretty ticked off.

Oh well, I had hoped that this anecdote might help someone. But I honestly don't think it can. I think in order to help, you pretty much have to end on an optimistic note, a plan of action, or a lesson you've learned... OK. Here's the lesson: when discussing possible bathroom incursions, I've learned that it's best to get the blueprints directly from the plumber.

Fare well friends. Keep those seats down.