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Plumbing in the Home/Plumbing drain/vent problem


QUESTION: Have a double sink set up in the bath vanity with pop up drains.  The sinks do not have an overflow.  The sinks drain each loop after the trap around the back of the vanity to the base of the vent stack.  They both come into a  "T" and then downward to the sewer line and the vent line is right above the T and heads up to the roof..  I have snaked the drain lines and the vent stack and all is clear.  Problem is the sinks especially when filled together back up and do not let the waste water empty.  There seems to be a "vapor Lock" type situation.  I do not have enough room under the vanity to install an air vent but I could install it about 6" before the waste lines enter the sewer drain and the original vent stack.  Your thoughts

ANSWER: Dear Gene, you could certainly try to add a mechanical vent beneath the sinks... from your description though I am not sure that would solve the problem though.  Perhaps the waste pipe is under sized for the double sink setup?

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QUESTION: from the tail the waste travels through a 1 1/2 PVC around through the back wall and
T's into the waste and vent which are 2" PVC.  Further description-  each sink travels it's own route to the waste and vent pipe they do not marry under the vanity and then as one waste run into the 2" main drain.  As a thought since they come together into the T would a soft curve rather than a T conection possibly help this "water lock" problem?  If you run one sink at a low water inlet flow it runs fine with no apparent backup.  I am really puzzeled.


That is a bit puzzling Gene, Some type of offset would probably help the two sinks drain better.... perhaps a "Double Wye" fitting or two "Wye" fittings one above the other.... Another possible concern would be the pitch of the drain pipes.  I had been assuming that they would be vertical in the wall.... what about after though... could there be a back-pitch in the line somewhere?

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Thomas Ambler


I am experienced at troubleshooting and solving all types of plumbing problems. Issues related to specific manufacturers fixtures and specifications though are beyond my field of expertise. I have dealt with problems in both rural and urban areas, and with water supply and drainage systems. Plumbing issues can be very obscure... such as odors, stains or occasional seepage. I have even had to chase rats from a customer's sewer line.


I have 25 years experience dealing with plumbing systems (which also includes hot water and steam heating systems). My main expertise is in diagnosing and solving problems. I have worked in construction and installation of new systems but do not regard myself as an expert in that area.

Asbury Park Press, Seattle Times, Denver Post.

I completed high school and one year of college. I served 4 years in the Marine Corps and have education in electronic and electrical troubleshooting and repair. I have attended classes on installing and repair of oil burners, and I have EPA universal certification for air conditioning and refrigeration. I am now enrolled as a full-time student at Everest college to re-train for a new career. Any donations of financial support would be greatly appreciated.

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All of Denny's Restaurants in NJ, Several Burger King stores, I have done work at two different homes for Bruce Springsteen. I have also worked for Jim Johnson (of J&J) and his family, Whitney Houston, Steve Forbes and many others.

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