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.

  • Well, the floodwaters subsided, and when they did, the toilet was flushable again. Until that point, we urinated in one toilet - the slow drainage was sufficient, and tried not to defecate. Luckily, the sewers cleared before it was a major issue. Commented Aug 30, 2017 at 4:53

3 Answers 3


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!

  • 1
    For drinking water, we had a lot of bottled water ready. For waste, we had a bucket, but no sawdust. I was going to fake it with used charcoal, and my wife figured that if it came to it, we could put a lot of kitty litter in the bucket. I'm happy to say the plumbing came back before we hit that point. Commented Aug 30, 2017 at 4:56

Scott, I'm not a plumber but I think I have been through just about anything plumbing issues can throw at you. I think you provided enough information to get it figured out. I don't think it's item one below since you said it's only an issue when you have torrential rainfall. BUT. One comment made me address this too.

  1. When you said the toilet fills up somewhat when flushed, it leads me to believe your tank is not filling up and getting enough water for a complete flush. - Pull the lid off the back of the toilet and make sure it's filled up before you flush. (should be a water mark / stain showing where the normal level is) If it's not full, it won't flush properly. Get some water from another faucet and fill the tank up and flush. If that works. Good. If not, you have another issue.
  2. Since you are in a municipality (mud district), your house and the neighbor directly behind you are piped into the main sewer line. (All lines run out the back at connect to a center trunk basically. There should be a PVC cap just behind your house (maybe 2-3 feet from the house). This cap should be screwed on (threaded - not glued) This is there to remove for cleaning the line out going either way. (toward the center trunk or under the house and into the toilet). Take that cap off and see if it's full of water/sewage. If it is, your line is either plugged up, collapsed or the main sewer is full. Good Luck
  • Thanks for the advice. I'll check the toilet now, and go hunting for the clean-out valve. Commented Aug 27, 2017 at 21:52
  • Don't assume sewer lines are behind the house, ours and many others run down the middle of the street.
    – Tyson
    Commented Aug 27, 2017 at 22:11
  • It happens that mine are behind the house. (I had a lot of plumbing work done a year and a half ago, so I learned that much.) Unfortunately, even though I have clean-outs for both the bathroom and our kitchen/utility room, I wasn't able to open either of them. The bathroom one is under two inches of water, and neither of them will open. Commented Aug 27, 2017 at 22:20
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    Sometimes screwed-on caps cannot be turned because they are under hydraulic or pneumatic pressure. You might be LUCKY that you couldn't open them, where all of the neighbors' sewage might flow into your home.
    – Upnorth
    Commented Aug 29, 2017 at 17:20

This link from bobvilla.com gives a pretty thorough explanation plus some "don't dos": https://www.bobvila.com/posts/55864-toilet-won-t-flush-after-a-heavy-rain

Unfortunately this means that you neighbors and local businesses and hotels are likely/potentially experiencing same issues. Only quickly deployable solution that comes to mind are port-a-potties.

Sorry you are stuck in this mess...best of luck.

  • Unfortunately, the poster of that post says he has a septic system. How much of that advice applies to me, with municipal water? Commented Aug 27, 2017 at 21:15
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    I noted the possible difference while reading the link, but I think same principle still applies...essentially, the flush water has no where to go at this point. Might be worth a call into the city, although I suspect they may be inundated (in more ways than one...).
    – AA040371
    Commented Aug 27, 2017 at 21:27
  • Well, it says that other things drain slower than the toilet, which makes them seem less prone to getting stuck. And I guess we get slow seepage into the overfull main lines. The implication seems to be that I can do some rinsing/washing in the sink, as long as I keep the outflow volume low enough to let the seepage handle it. I would think both dishwasher and washing machine would be bad ideas in that circumstance. Commented Aug 27, 2017 at 21:35

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