Question about moving a drain line.

[Coast]

I have two separate 4" drain pipes that my fixtures connect to, and I want to move 2 fixtures to the other pipe.

Here is a diagram of the situation. Everything is in the crawlspace, and everything is vertical except for the 2 drain pipes, and the line I want to move.

Will this work? If so, where should I connect the line I want to move?

Thanks for any help. Location is Arkansas.

 

[oz-plumber]

It shouldn't be an issue because the fixtures on drain 1 are vented and going into a 4" drain - presumably vented also.
Distances may / could be a problem, so I would run the 4" drain to as close as practicable to the fixtures on drain 1

 

[Coast]

Thanks Oz. I might not have explained it clearly... the 4" drains (marked 1 and 2) are not moving, I just want to move the 1 1/2" sink 1/washer line from drain 1 to drain 2.

The only difference with the final configuration will be that I dont believe drain 2 has a vent, and I wanted to make sure that introducing the vent from the washer line into it would disrupt anything. I wouldn't think so, but wanted to double check.

Also, what would be the best place to introduce that line into drain 2? On the end where the toilet is?
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Here's a more concise diagram for what I want to do:

 

[oz-plumber]

That fitting looks fine and suitable

 

[Chuck]

Here's a more concise diagram for what I want to do:

In my opinion, before making such a change, it's always worth wondering why the current system was done that way in the first place.

As it stands, Drain 1 appears to be 'greywater' only and Drain 2 appears to be 'backwater'. You might want to check whether this separation is coincidental or whether the drains go to separate destinations, e.g. a septic tank for blackwater and a reed-bed filter or conservation system for greywater.

 

[Coast]

In my opinion, before making such a change, it's always worth wondering why the current system was done that way in the first place.

As it stands, Drain 1 appears to be 'greywater' only and Drain 2 appears to be 'backwater'. You might want to check whether this separation is coincidental or whether the drains go to separate destinations, e.g. a septic tank for blackwater and a reed-bed filter or conservation system for greywater.

Hey Chuck, thx for the input.

Drain 1 was original to the house, built in the late 60's, and toilet 1 was attached to it, along with kit/bat sink and tub.

In '79 they remodeled the house, and installed drain 2 (added a washer to drain 1 and moved the toilet/bath sink to drain 2).

My mom likes to tell the story about how drunk some of the remodelers were, so who knows how much planning they did, hah (although those guys might not have worked on the plumbing).

Both drains initially went into a septic tank, and eventually they got hooked to the city sewer.

I've been doing some reading on venting, and it seems like the safety concerns would be traps draining and letting sewer odor up, and/or slow draining/backup. I figure any of those issues would be quite noticeable, and if they arise, I can either figure out a venting solution, or just move it back.

Both drain pipes are within 8' of each other, so it wouldn't take much work to move it back if I have issues.