I have two full bathrooms. When the upstairs bathroom toilet is flushed, it creates a powerful bubble in the downstairs toilet. Both toilets flushes OK and I see no evidence of any clog in either one. Also all other water in the house runs and drains properly.

Thanks for any info you can provide.

Sounds like there is a small clog in the sewer line. Bubbles don't just happen by themselves. Have you tried plunging downstairs toilet? If nothing seems to be clogging then if it does not back up downstairs... then the bubble is something you'll just have to live with until it does start to overflow and you can pinpoint clog better. The clog would be downstairs not upstairs. Did little kids live there before you moved in? Possibly they may have flushed small toys down the potty and they are stuck... not enough to cause a real back up but just enough to be annoying.

I would look for a clogged main.

I think that the bubble is your toilet trying to vent back out the lower fixture. Rod the vent stack from the roof if it is safe to get up there this time of the year. Run enough rod to reach roof to basement floor and about 20" more. You have not indicated that the lower toilet has overflowed with sewage so I lean toward the vent.

I would have to say look on top of your roof and right above your bathroom you should see a stink pipe. You need to get on the roof and have a look down it. If you have ice build up in the pipe then it will cause this problem. Pore windshield washer down the stink pipe that is for -40 Degrees. I hope that will fix it for you considering it's winter.

Questionhelp, I think your stink pipe is what we call the vent stack. Windshield washer fluid may help if it were frozed but they usually plug with other debris. Rodding is a great solution to all of the crud that can go down a vent including ice, which I have never seen happen. The sewer gas coming up a vent is usually between 55 and 70 degrees.

I see my company deals allot with this type of problem this time a year. It looks like a very good option. Checking the small stuff will help people rectify the problem. And plus all my plummers call the vent a stink pipe. It makes more sense to the customer that needs incite of the problem. Thanks for you for your help