What's the minimum height for a high efficiency front load washing machine standpipe assuming the P Trap is no higher than 12" from the Floor? General plumbing rule of thumb seems to be 36" from floor. I'm also reading suggestions of 18" above the trap weir as a minimum. Additionally I'm seeing that the minimum height should also be above the maximum water height in the washing machine drum to prevent siphoning. With older top load washers I can see where a higher water height would necessitate a higher standpipe and hence the old safe 36" height rule of thumb. But with newer front load machines it seems the water height is now lower especially if the machine is not on a pedestal. So if my trap weir is at 12", my maximum water height in the machine is say 20", can I put the standpipe height at 30" or can I get away with it being even a little lower? Reason I need it to be no higher than 30" is so that the entire standpipe box surround which includes the water supply lines is below the height of the counter that runs above the machines. Thanks.