Apologies if this isn't exactly on topic, but I found Why will my toilet not flush after it rains or when ground is wet here, and my question is similar, so hopefully I can get a response.
I live in an area very susceptible to floods, and we're in the middle of the results of Harvey. To be clear, that means cataclysmic flooding throughout the city. Bayous are overflowing, and it's likely that all of the city sewers are as overrun as they can be, and may be backing up.
I know nothing about plumbing (though I know that we use the municipal system, not a septic), and we currently still have running water. All of the sinks seem fine – water comes out of the faucet and down the drain. But when we flush our toilet, the bowl fills up somewhat and slowly drains down. The tank refills properly. This happened first with one toilet (which, if it matters, is closer to the sewage line), and eventually has happened with the other toilet. We've had the exact same behavior with the other massive floods over the past few years.
My interpretation is that the city sewage line is sufficiently backed up that what we flush sits in our pipes connecting to the sewage line, and once our pipes fill up, can't go any further.
What does this mean to us? Obviously, try to limit our use of the toilets until the city sewer system recovers. But I don't know enough about what lines go where. Is it safe to run the sink? Can I still wash dishes? There's no great need for it, but could I use the washing machine? I'd assume all lines would back up equally over time, but I know there are differences between sewer lines and whatever the other lines are called that go out of our house.
Are there any recommendations for being able to use the toilet? "Hold it in until it's over" doesn't work when this flooding may go on for literally a week.
I've also looked at Toilet not flushing after flooding, but the consistent behavior during floods and only during floods seems to imply that our line hasn't collapsed.
Best Answer
Once your main sewer line becomes flooded you will not be able to use any plumbing that drains to the sewer. It will all back up into your house.
You should bottle some water for drinking and use buckets with sawdust for defecating if you have them available.
The flood waters will be polluted with seriously bad stuff and can make you pretty sick so try not to contact them if you can.
Good luck!