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December 9, 2008
Imperfect Pitch
Q: Dear Ed, our home was built by the previous owner, and we have had problems with our bathroom sink plugging up. When I investigated the drain line in the basement, I found the drain line to be running uphill instead of downhill. I installed a new line with the proper pitch and now the sink drains fine. However, now we keep getting a sewer smell from the sink. What is going on and how can we fix this?
Jim (Texas)
A: Well, it seems the previous owner made two mistakes.
First he installed the drain line with what's called a "negative pitch." That means the pipe does not run downhill from the fixture, and it will eventually plug up. Now that you have installed a drain with perfect pitch, it should be draining much faster.
However, this may be creating a vacuum in the line and my guess is that... problem number two: there is no vent on the line to break the vacuum. This may siphon out the trap water, and there's the issue. When a trap is empty, sewer gases will get in through the drains.
You may need to install a vent line or "auto-vent" control on the drain to stop trap siphoning (and the bad smell.) And trust me, this is not stinky advice: Always call in a licensed plumber to help out with any home plumbing vent problems!
Ed Del Grande, the author of Ed Del Grande's House Call, was born and raised in a family-owned plumbing business. With more than 25 years of experience in every aspect of construction, he holds current Master licenses in pipefitting, fire protection and plumbing. If you have a question for Ed, send him an e-mail at eddelgrande@hgtvpro.com.Posted by Ed Del Grande at December 9, 2008 10:25 AM
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Comments
"Always call a licensed plumber to help out with any home plumbing vent problems". We've had this discussion before and nothing changes. Since you're a licensed plumber you feel you have to "support the trades", but the proper installation of an in line vent does not always a licensed plumber. Many outlets who sell the product have sales pros willing to help homeowners. People still thank me long after I retired for the advice given when they run into me. By the way you did not mention that some jurisdictions don't allow in line vents.
Posted by: John at December 24, 2008 3:14 AM
An easier fix (less expensive) would be a 3" offset available at most home centers.
Posted by: fredew1 at December 26, 2008 7:02 PM
The orginal drain may not have had a trap installed. When homeowners do their own work they don't understand the rules.
Posted by: fredew1 at December 26, 2008 7:05 PM
