Dual drain lines going into slab for kitchen sink?

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Old 12-09-12, 11:41 PM
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Dual drain lines going into slab for kitchen sink?

Our house built in the 1950s has two drain lines going into the slab for the kitchen sink. Only one of them is in use because the other one has a crack at the base.

I noticed that newer sinks have the two sink drains go to the Y inside the cabinet. That's how ours is setup now due to the crack in the 2nd drain.

Why did older houses have two drains into the slab, compared to a single one these days? How far down the slab do they usually join together?

I am thinking whether it would be worthwhile to repair the base and use both, since the wall is opened up now for new cabinets.
 
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Old 12-10-12, 12:04 AM
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The only thing I can think of is one is old and one may be newer. Septic years ago then they brought in sewer. Slab so ran new lines?

Or somtimes they had separate dry wells. The sink normally went to dry well instead pf septic. Possibly it was double basin????

Too many variables... Show pics.. I am curious.
 
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Old 12-10-12, 12:25 AM
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Here's a pic. Almost certainly the two drains went into the foundation at the same time in the 1950s. The home used to have a septic tank. Now we're connected to the sewer system, but that wasn't until the 1990s. The floor was not opened up since the 1950s.

 
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Old 12-10-12, 07:38 AM
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Both pipes appear to continue upwards. Are they both vented up through the roof, or do they go to a 2nd floor?
 
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Old 12-10-12, 07:42 AM
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Both are vented to the roof. The two roof vents look identical.

The plumber, a really experienced guy, came over today for some other work and looked at it. He didn't know why there are two drains going into the foundation. Is this really uncommon?
 

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Old 12-10-12, 09:18 PM
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I talked to another plumber. He thinks there are two of them because these drain pipes are 1 1/2" while the standard size is 2". He guesses that it makes a Y into a 2" line right below the slab.

This is turning out to be very interesting because no one really knows for sure, so far.
 
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Old 12-10-12, 09:31 PM
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I talked to another plumber. He thinks there are two of them because these drain pipes are 1 1/2" while the standard size is 2". He guesses that it makes a Y into a 2" line right below the slab.
No way... Plumbers did not think like that or plumb like that back then. There were 1 1/4 lines on single sinks and such back then.


I am thinking dual residence if anything from when the house was original. Like a duplex. Probably a wall separating the two....


 
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Old 12-17-12, 10:08 AM
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Plumbers is working on it right now with the jackhammer. Found the Y about a foot below and a couple feet forward along the slab. I'll just have that portion up to the Y replaced with ABS. I will have a double basin sink again. I like the dual configuration, it's kind of cool and unique with two vent pipes. But I still wonder why it was done like that originally.
 
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