Re: Basement toilet splashes when 2nd story toilet flushes
Posted by a on February 06, 19100 at 22:51:19:
In response to Re: Basement toilet splashes when 2nd story toilet flushes
I'm not a pro, but I know enough to know you've got a serious problem that needs to be fixed ASAP. If you don't get advice from a pro on the board, you need to hire a pro. That or learn a lot about plumbing.

Here's the situation: modern plumbing requires venting of all fixtures. It also requires venting of the main soil stack. Either of these things guarantees that you should never have an air pressure problem in the downstairs toilet. If you're having a problem, both are out of whack.

Wastes coming down the soil stack may increase air pressure below as they fall, but that pressure should be vented by 1) the vent line off of the toilet's soil pipe and 2) the vent off the main soil stack.

In other words, the pipe where the nasty stuff goes when it leaves the toilet is not only conected to the sewer, it's also connected to the vent pipe on the roof of the house. Increased air pressure as wastes come down the soil stack should vent through that opening to the outside air. The water in the bowl may tremble a bit, but it shouldn't splash.

Even if the soil pipe is not vented, you should still not have a problem, because of the vent pipe of the main soil stack. In other words, somewhere at the bottom of the soil stack, below the all of the places where the house fixtures connect, there's a vent connecting the soil stack to the pipe on the roof of your house. Even if none of the fixtures in the house are vented correctly, this vent on the soil stack should allow air pressure to escape through the roof vent, again avoiding splashing in the downstairs toilet!

So, it sounds like you've been boogered both coming and going by the previous homeowner (you can guarantee that this was not installed by a professional plumber). He installed the toilet without venting it properly, and to make matters worse connected the soil pipe out of the toilet directly to the sewer line, *below* the level of the vent stack. Bad, bad, bad, and actually very dangerous.

Now it's always possible that everything is installed correctly, and that you've just got clogs in both the toilet's vent pipe and the soil stack's vent pipe, but this just doesn't seem blooming likely to me. Get a plumber, show him the situation, bite the bullet and get it fixed before you end up with sewer gasses in the basement.

: Please help! My house is a colonial with 1 bath upstairs and a toilet in the basement. When the upstairs toilet is flushed, air pressure backs up into the drain for the basement toilet, causing water to splash out of the bowl. I've had the house's main drain line snaked a couple of times in the last two years and replaced the basement toilet. Still have the same problem. Does anyone have an idea about what might be causing this?

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