Toilet bowl gurgling while tub is draining

Do you have a septic tank? If so, when was the last time you pumped it?

Negative. City sewer system.

You got pluggage further down the line. When the tub drains, instead of flowing down the line, it backs up and pushes air out the path of least resistance, usually the toilet. That’s why it gurgles. It may fix itself, or it may back up and overflow the toilet. I’ve learned about this stuff the hard way. My issue was due to high quality toilet paper like Charming holding together too well as it went down the line. We switched to Angel Soft which quickly softens once wet, and haven’t had a problem since. I have cast iron sewer pipe.

Had a plumber tell me he put his daughter through school thanks to Charmin Ultra

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You got pluggage further down the line. When the tub drains, instead of flowing down the line, it backs up and pushes air out the path of least resistance, usually the toilet. That’s why it gurgles. It may fix itself, or it may back up and overflow the toilet. I’ve learned about this stuff the hard way. My issue was due to high quality toilet paper like Charming holding together too well as it went down the line. We switched to Angel Soft which quickly softens once wet, and haven’t had a problem since. I have cast iron sewer pipe.

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Bolded is correct.

My line plugs occasionally ever since the sewer upgrade project in BR. I think they did a bad job of connecting me to the new sewer line and stuff catches on a lip or something. I use a bladder attached to a hose that puts line water pressure on the sewer line (inserted at external clean out port). This clears it every time. The line stays clear anywhere from one year to 3 days, but it always clears with the bladder attachment.

I’m crude and leave my clean out port fitting loose so whenever I have pluggage it just overflows outside and doesn’t cause an issue inside the house.

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I’m crude and leave my clean out port fitting loose so whenever I have pluggage it just overflows outside and doesn’t cause an issue inside the house.

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I would say you are wise, not crude.
Why take a chance on a giant mess in your house instead of a mess in your lawn that can be hosed down or wash away in the rain.
ESPECIALLY if it was caused by someone else's incompetence.

You could have a blockage along your outflow pipe. This happened all the way near our neighbor's house due to bad city sewer construction.
However, it could also be a blocked vent stack. Bird or rodents nests can block the vent pipes so that the pressure of draining is not relieved upwards and causes gurgling back somewhere else. Most often noticed in a toilet. A hose down the stack pipe might clear this mess.