I am not sure if our problem has to do with the washing machine or the plumbing. I tried reading other answers to similar questions on this forum, but not sure if the answers apply to our problem. We have been using the same washer in our basement for 7 years. It had an overflow problem at the drain hose/stand pipe juncture once before, when both the washer drain pipe and the kitchen sink backed up. We fixed it by pouring drain declogger down the kitchen sink. Everything worked fine for 3 years after that. However, recently we have had problems again. This time our kitchen sink is draining fine, but the overflow problem at the standpipe is worse than before. We tried putting drain declogger down both the sink and the standpipe but it didn't help. We even opened up the standpipe and it was clear of clogs. At the main metal pipe which drains both the sink and washer out of the house, the washer drain line is connected first, then the kitchen sink drain line enters a few inches down the metal pipe, which then leads out of the house. This would suggest that there would be a clog somewhere prior to the kitchen drain connection. However, we poured a gallon of water down the stand pipe, it seemed to drain fine. Is there anyway it could be the pump in the washer? It is old. Is there anyway back pressure would build up somewhere because of the washer pump? Thanks.

Sounds like you need to run a sewer cable down the washing machine drain. It has a buildup.