Had some bathroom remodel work done a few years back; installed two new toilets, replaced the pipe to the shower. When we flush one toilet, the other bubbles up in the bowl. Had a plumber snake the line, check the outlet valve on the roof, took both toilets out and reinstalled, and he couldn't figure it out. Could the shower pipe the worker replaced (at the shower floor) be the problem? I've put up with this annoying "two toilet flush" for 5 years and no one seems to have an answer. Sure appreciate the help.

Before I answer your question answer this one. What do you mean b y,
check the outlet valve on the roof What's a valve doing up on the roof? Back to you. Tom

Plumber went on roof and snaked the roof pipe, as I recall. I think what I'm talking about is the outlet pipe. He also snaked the sewer line. My concern has always been that when the sub contractor replaced and soldered the new shower line at the floor, maybe he didn't do it right. Thanks for answering so quickly!

When we flush one toilet, the other bubbles up in the bowl Well something's causing a back up, When the plumber had the two toilets out did he snake both drain lines? Can you describe what he did to the shower drain?

I believe he did snake both drains, but I'm not sure now since it's been quite some time. Re: the shower: House was built in late 70s (not really good construction, typical tract development). We tore out shower floor tile (no shower pan, just tiled directly on concrete slab), copper water line to shower
(no tub) was corroded, he cut out old pipe, soldered new copper line in. I do remember that part. So, could that roof vent just need to be resnaked?

OK! Here's the thing! Bubbles indicate a partial blockage. When you drain or flush the discharge runs down the drain line and hits a partial blockage and bounces back sending a bubble of sewer gas ahead of it. There's your "bubble". Now if no other fixtures are affected then the blockage has just got to be close. The toilet drain lines come to mind. He snaked everything else If he didn't snake the toilet drain lines when he had the toilets off he missed the boat. That's where I would start. I can't see replacing a section of the shower drain affecting the toilets. Regards, Tom

You are awesome and live up to your "Speedball" name! Thanks so much. So, can I just run a snake through the toilets or do I need to remove them to run a snake? Thanks so much!

Both toilets will have to be remover to snake the drains, Good luck, Tom