Washing Machine Drain Backing UP
I am having a serious problem with my washing machine drain. First some background, I live in a 1 year old double-wide manufactured house. The washing machine drain is 1-1/2". The top of the drain is about 4' off the floor. The drain goes down about 28" before the "J" trap, then over about 6" and then a 90 degree. At the 90 degree a pipe goes down under the house and a pipe up for the vent which has a mechanical plumbing vent about 18" up.
Now here is my problem, I own a Maytag washer that's about 12 years old. The washer drain is backing up and coming out of the top of the stand drain pipe. The house manufacture has been here several times to try to fix my problem but as of yet nothing has help. The drain was first snaked, all clean. Then they put on a new mechanical plumbing vent, thinking it wasn't working right, didn't help. Then they went under the house and put in a new line going straight to the 3" and into the septic, no help. The manufacture says that it must be my washer putting out to much water at once but the washer has been in 3 other houses besides this one with no problems at all. I have asked them (many times) about the drain being 1-1/2" and not 2" and they keep telling that's not the problem. They also said that it could be my septic, something about a filter in the septic could get cloged if I use Charmin toilet paper. The gentleman that put in my septic says that it's not my septic because if it was it would backup other places in the house and not just the washing machine. Please help me!!
Thanks,
Scott