I live in a house with a septic system. When the winter/spring rains come, the toilet on the ground level master bedroom does not flush. We have another toilet on the ground floor that does flush. We have removed the non-flushing toilet, snaked the line and even installed a newer toilet. Nothing works until the ground dries out and then it will work fine. We had the septic tank pumped out, though it does tend to fill with ground water. What I don't understand is why will the one toilet work when the other will not? Any suggestions as to what the problem might be?

  • 3
    When you say it doesn't flush, can you elaborate a bit more? Is there no movement of water (overflows or fills up the bowl)? Does the water drain slowly without fully flushing? Does it gurgle?
    – Steven
    Nov 16, 2012 at 3:13
  • 1
    Why does one toilet work and not the other? The working one is probably farther from the problem, giving it enough open, empty drain pipe to allow an occasional flush. As Steven hinted at in his answer, if you flush it enough times, it will eventually back up.
    – bcworkz
    Nov 17, 2012 at 23:55

4 Answers 4


Septic System?? If so, the system is FULL of water already and needs to drain out from your drain field. If it is a municipal system, tree roots CAN SWELL TO 40 % or more of their normal size in wet weather, creating a blockage- hence a slower drainage- I'd look into a rooter service if this is the case and if on a Septic System- even pumping the tank will not help as the ground water is the culprit-preventing more water to disperse. Pumping the tank will only remove liquid & solids in the inlet side- not removing water from the leach/drain field.


I have the same problem. In my house, the toilet nearest the septic tank (outlet from the house) is the one that fails during extremely wet weather. A simple explaination is this is because the other toilet can empty its contents into the plumbing under the house and has more time to move to the septic. On the one nearest the tank, the pipes leading to the tank are already full (groundwater backup) and the toilet contents have nowhere to go. Sometimes I can force the water out with a plunge and get a single flush in, but it doesn't return to normal until after the rain stops. The same thing can happen with upstairs vs downstairs plumbing.

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. Aug 15, 2019 at 15:37

Some possibilities, in no order:

Vent Blocked

The toilets vent becomes blocked somehow when it rains. Check the vents on your roof for obstructions like trees, plants, birds nests, etc.

Damaged Pipes or Tank

Water is entering your septic system when it rains though cracks in pipes, seals or the tank itself and overwhelms your leach field.

In this scenario, a backup in your house would seem likely to occur eventually. When you are having the flushing problem, check the lowest drains in your house to ensure the sewer is not backing up.

Failing Leach Field

Your leach field cannot handle the volume of fluid when the ground is wet due to rain and might need replacing.

As to why only one toilet is a problem, with the exception of the blocked vent scenario, it is hard to say. I would try flushing the working toilet over and over to see if it slows down or stops as this would help rule out that one fixture or a broader plumbing/septic problem.


I have the same problem. We do not have a septic tank but live in a town house condo. The level of toilet water gets very low when it's windy and when it's raining a lot it will not flush. The water goes down very slowly only. I understand the water level in the toilet is because of the vacuum that is caused by the wind over the vent pipe on the roof so I assume this also causes the flushing problem. I live with it however.

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