Standpipe overflow. We have lived here for 2 years. Our new washer drains into a brand new standpipe that is higher than the washing machine. The plumper said all the pipes are to code, looks like new large piping and everything looks fine. He hooked up a garden hose and shoved it down the standpipe. We ran it at full blast the following day after the back up for in total for 10-15 minute. He said we ran so much water down there that he was confused as to where the back up was? For precaution, he snaked the line all the way out to the main sewer line. So we are a bit paranoid as to know when this back flow will flood our laundry room again. He said it was probably a back up that we had, but that he was not able to see it the following day. But from what I explained to him, he said it must have been a back up. However is also said it is possible the main city sewer line backup, which effected our place? The back up worked it was to us. I can buy a sensor to set off an alarm when this happens again, but is there something we can do to feel confident this will not occur again or catch it prior I looked into a valve that will close the standpipe if there is overflow. But this seems to be frowned upon? We can't drain this into a sink where we would be able to tell if it was slowly draining. I am trying to see if anyone has advice as to how to tell when we should expect a flood again? We did not see any drain issues prior? Knowing if your washing machine is draining slow is not really easy to tell? The second flood we had we never even used the washing machine which tells me the entire system must have been backed up. So this is a bit frustrating to figure out some type of heads up before this floods sewage into our laundry room again. Thanks for you help and advice.

I recently purchased a property and the basement was completely dry walled. Thus I have no idea what is above the ceiling or behind the walls. What I was interested in doing is installing a washer and dryer but of course the hot and water lines must be available behind wherever it is that I choose to install the washer. I also dont want to tear open drywall every which way to find the water lines. Where my water heater is installed they left the ceiling exposed and i can clearly see the water line for cold that enters the water heater and right above that is the plumbing for the kitchen and the bathroom is a few feet away as well. So I'm guessing I can just follow those lines. I also purchased a walabot to see if that would help and I think it will. Next to my water heater there is also a drain PVC pipe sticking out which would work for the drainage of the machine. Any help would be appreciated.