Plumbing - lavatory drains

I have two back-to-back bathrooms. Their lavatories are also back-to-back, and the same distance from the side wall. If I run the faucet in bathroom A while the P-trap in bathroom B is open (waiting for a repair part), the water from sink A will run out of the open trap in bathroom B. Is this normal?
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If they are installed with a "cross" or "X" fitting in the wall, likely water will gush across the opening and come out the open trap on the other side of the wall.

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Ray K wrote:

--
"You can lead them to LINUX
but you can\'t make them THINK"
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Ray K wrote:

Back-to-back fixtures are plumbed into a Double Sanitary Tee, like this one: http://tinyurl.com/44wyvs
(not necessarily this size one...)
Under low flow conditions, waste might not cross over, but a sudden draining of the basin might spill some out.
Jim
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http://www.drillspot.com/products/287050/Mueller_Industries_52820_3X3X2X2_Double_San_Tee I thought they had to use a "double fixture fitting", slightly different than a double sanitary tee. Like this one:
http://www.drillspot.com/products/364227/Approved_Vendor_02247G_Double_Fixture_Tee
Cheers, Wayne
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Wayne Whitney wrote:

http://www.drillspot.com/products/364227/Approved_Vendor_02247G_Double_Fixture_Tee
Good call, Wayne. Thanks.
<back to my buggy whips...>
Jim
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Speedy Jim wrote:

Flogging a dead horse, here's an interesting discussion of double Tee's and the application of the 2006 Code requirements: http://www.terrylove.com/forums/showthread.php?t 788
Jim
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Wayne Whitney wrote:

http://www.drillspot.com/products/364227/Approved_Vendor_02247G_Double_Fixture_Tee
so maybe it wasn't required back then.
In response to others, the water flowed out the open trap even with modest amounts of water running in the other sink from simply turning on one faucet. In other words, I didn't fill one sink then try to empty it quickly by raising the popup suddenly.
Now that the p-trap is reconnected, all is working properly.
Thanks to all who responded.
Ray
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wrote:

Yes, especially if there is a lot of water draining in sink A.
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If the pipes are sized and vented properly this should not happen even though it can. In your case, the open P trap is lower than the basin so it is certainly more likly than otherwise. In fact, the bottom of the P trap is lower than the connection to the drain, the flow may be inevitable, there's no uphill, just a short 2" hop across the pipe.
You may want to just run a snake down the drain from both sides just to make sure there is no partial obstruction slowing the flow and waiting to clog. Good idea to do this once a year or so with bathroom drains. hair and personal products clog drains fast and bath sink drains are often only 1.5"

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