What causes pipes to make a moaning/gurgling sound after flushing toilets? And how can I fix it? We live in a 107-year old house and have lived here for the past three years. About a month or so, we started to hear our pipes after flushing the toilets. You can hear the sound from one of the bathrooms, which has an inexplicable drain in the floor (the primary source of the noise). It basically sounds like you can hear the water/waste gushing down the pipes. The sound starts after the toilet bowl has completely emptied. We hear the noise in the same place (which is on the second story and the only place you hear it) regardless of whether we are flushing a toilet on the first, second, or third stories. We have four toilets and it makes the sound for every single one (making the most sound with the third story, presumably because it has further to go). Why would this suddenly start happening and how can we determine what's gone wrong and fix it? THANK YOU!

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What causes pipes to make a moaning/gurgling sound after flushing toilets? And how can I fix it?

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Your pipes are attempting to vent through the fixture traps. Check the vent pipes for a clog and snake and clear the vent you find clogged. Good luck, Tom

Can you safely walk around on your roof, that's the best place to rod the vent stack. Use enough rod to reach roof to basement floor and then 10-15' more rod.

Thank you for your quick responses!
As a follow-up question -- how urgent is this repair? In other words, how long do I have before something really gets out of hand? We do have good roof access but we have three stories and the first and second have 9-10' ceilings, so we'll need a much longer snake/rod than we have! Is this a common repair that plumbers are called out for, and is it generally costly?
THANK YOU!

Just checking back again to see if anyone can tell me how serious of a problem this is and how long we can leave it as-is before it gets much more complicated to fix. Thanks!

How serious? If everything is still draining you are just partially block so your house isn't going fall apart tonight. However, the partial block built up over time, once there is a partial blockage it will collect debris faster and faster, eventually leading to a complete backup. That will be pretty messy and stinky and usually at the most inopportune time. It is a common repair issue for plumbers and most all will have the proper tools. Cost varies depending on where you live but the service call and time will likely be about $250 if there are no other issues found. Most plumber will give you a ballpark estimate for rodding the vent stack.

Thank you!