We are redoing the master bathroom in a house we just purchased. We have the washer drain pipe tied in with the shower drain. The shower drain is within 3 feet of where the drain goes below the slab. There is a vent going up to the roof in the middle of the washer drain line. When we run the washer, the water is backing up into the shower drain. It seems to start coming out as bubbles first.
I have tested with running water through a garden hose into the washer drain at full blast and there is no backup. Could it be the detergent bubbles causing the backup?
Would a second vent closer to the washer help? Or is it just the higher volume from the washer not able to go through the drain as it is? We have 1.5" pvc pipe for the drain lines.
Thanks for your help. Any suggestions are appreciated.