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FIGURE A
Click Image to enlarge.
Q I live in a ranch home with
the washing machine and
toilet in adjoining rooms. When
the washing machine discharges
water, air comes bubbling up
through the toilet. Sometimes
the water level in the toilet will
drop, too. The washing machine
connects to the house sewer line
before the toilet does. What’s
going on, and what’s the fix?
Robert Fisher, Decatur, IL
A You’re seeing signs of poor venting, that is, your drain line is gasping for air. When you pour liquid from a can, you’ll notice that it doesn’t flow evenly unless you have a second opening for air. The same holds true for plumbing. As water goes down a drain, air is needed to equalize the pressure in the drain line.
This is the purpose of a venting system. If the drain lines in your home have poor venting (as in Figure A, for example), water rushing down the drains will pull water from nearby P-traps. The drain in the toilet bowl is basically a P-trap. If the problem just started, it’s probably a blocked drain or vent that needs to be “snaked” out. And since the water in the toilet is dropping and gurgling, it’s likely that the problem is near that area.
Unfortunately, a clogged or missing vent is tough to fix, since it usually requires breaking into the walls to examine the drain system. Unless you have plumbing experience, this project is best left to a professional.
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