I'm designing a drain-waste-vent system to handle two baths and laundry. I'll be tying into 4" ABS sewage line, that has a 2 inch vent (See figure 1). It's a Single story house with crawl space, in Southern California with very moderate temperature. All venting will go straight up through roof.


  1. Are there enough vents (i.e. does the washing machine need its own vent)?
  2. Is the location of the vents correct?
  3. Is the plumbing sized correctly?
  4. Any problems with this design?

[![Existing Plumbing][1]][1]
Figure 1

Proposed design Figure 2

The floorplan for Bathroom B has changed and now I have a new design. Many thanks to forum participants for all their tips. Please let me know if I am on the right path to a good and UPC code worthy design. Is the venting correct?

enter image description here


2 Answers 2


Every code authority is different. From what I was told when remodeling my house over the last 3 years, is that draining appliances on the same walls can share a vent. Each wall would need a vent. Same drain line is fine, but the vent needs to be within a certain distance of the appliance. I have 1 2" vent that my kitchen and bathroom use, on the same wall. My washer has its own, and my second bathroom has its own.

  • From memory as long as it is within 6' it would be ok I like the vent to be close to the toilet because it is the one for sucking water out of the traps.
    – Ed Beal
    Jan 2, 2019 at 22:22

All looks great man. Only changed I, personally, would make is to get to 4" piping sooner as close to those two toilets as possible. I know you have cleanouts, but you don't want to use them.

That is only personal preference though, not a requirement.

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