Plumbing back to back double sinks

[edtuck]

I am a DIY homeowner and I am converting a portion of my den into a master bath. The vanity is going on the same wall as the vanity in the main bath, but on the other side. It seems most efficient to let these four sinks share plumbing. I was planing on using at least 2 double fixture fittings for the sinks that are back to back and then probably a double fixture fitting to bring the waste from the back to back sinks together with the ones to the right and left. I am attaching a diagram of my idea and pictures taken from another site of the two concepts I am combining. I also believe I may need to add a clean out below each of my Double fixture fittings. I am thinking I may not want to use a double fixture fitting where things combine because it just adds another vent which is not necessary. The plumbing then becomes a single square rather than a bisected square. I think I could also choose a side and have the vent come up rather than centering it between the sinks as well. All waste and vent pipes will be 2 inch. Thank you for any replies. I am in Los Angeles, County in California and must therefore adhere to their codes.



After looking at my diagram again, I realize that I did not draw the double fixture fitting correctly where the back to back sinks combine. Imagine the bottom line lower to allow for the vertical draining of the double fixture fitting. Sorry. Thanks again for any suggestions!

 

[hj]

You also need a "double combo" where the two drains connect to the verical riser, but more specifically, you do NOT even need the center riser vent between the top and bottom "crosses" because it is just cosmetic. IF you leave it there, the top one CAN be a sanitary cross instead of the more expensive back to back fixture fitting.

 

[Sponsor]

 

[edtuck]

Thanks hj! I was thinking the center riser wasn't needed. So If I get rid of that, do I still use a double combo where the drains combine, but put a plug in it? Is there another fitting that is like a double combo without the vertical? Or Possibly, I just run both fixtures over to one corner and use a regular combination Y-1/8 and then I only have the two inlets. I just want to make sure I am not creating an S-trap anywhere as well. The sinks will be about 3 feet apart because they are both double sinks on a 60" vanity.

 

[hj]

There are MANY ways to install it without the unnecessary center riser. A Y with a street elbow on top of it, and an 1/8 bend at the same elevation as the street ell would be one of them. If the riser is at one of the two locations you do NOT need a combo to connect the drain from the other sinks, since a sanitary tee would be all that is required.