Sorry for opening up this thread again after so long after the last comment, but I was wondering about the revent shown in the previous post photos. I was under the impression (and I certainly could be wrong) that normally the revent line needed to rejoin the stack above the height of the overflow of the fixure being served. (I understand that there are some exceptions for use in places like a island kitchen counter where other methods are used.) In the picture, it appears that the top of the washing machine standpipe is above the revent tie-in point to the stack.
As it was explained to me, the reason the revent line tie-in point should be above the overflow level was to prevent the revent line from becoming the drain line in the event of the actual drain line being plugged up at a point downstream from where the revent line ties into the drain line. If a plug occurred in this area, drain water would seek it's own level, and would flow up the revent line, across the horizontal portion of the revent line, and then down the stack to the primary drain.
Obviously if the revent show in the pictures is wrong, it might be possible to just cut it a bit off the standpipe and still be within the limits for the standpipe height and distance from the trap weir, and simultaneously get the standpipe overflow height lower than the revent height.
I guess my questions are:
1. Does the revent tie in point on the vent stack always need to be above the overflow level of the fixture it serves (except for the special cases like island kitchen sinks)?
2. Do different rules apply (or are different arrangements normally acceptable) for washing machine standpipes and revent lines?