I am trying to help sort out a sewer issue in a renovation project. The pictures show the general layout. Working left to right, (2) water closets/sinks enter the double wye which was later changed to the second picture to try and alleviate the problem. The next double wye picks up a shower and a tub and then everything exits to the right. The main line is 3" PVC and the longest run is approximately 15 ft with a slope of ~1//8"/ft which appears to meet the codes. The problem occurs at the beginning where the water backflows up the opposing line ~3 ft and then slowly drains down. Each fixture is vented. There are 12 fittings along the trunk due to the joist direction relative to the trunk line
Is it as simple as increasing the fall to 1/4"/ft? Are there frictional forces from each of the fittings that need to be accounted for some how? Any suggestions?
Thanks
Is it as simple as increasing the fall to 1/4"/ft? Are there frictional forces from each of the fittings that need to be accounted for some how? Any suggestions?
Thanks