We just bought a new house and the sump pump and or lines make strong popping bang every time we use the washer and it's draining or we are using several drains, the contractor says its normal I don't think so. Any ideas? It has been doing it seen we moved in ( a month)

We just bought a new house and the sump pump and or lines make strong popping bang every time we use the washer and it's draining or we are using several drains, the contractor says its normal I don't think so. any ideas? it has been doing it seen we moved in ( a month)

It may not be "normal" but it is explainable. I don't get complaints as much on drainage as I do on the water lines popping and creaking after use.
Your washer discharges hot water. This causes the pipes to expand and contract. If the pipes are strapped or tight against a stud you can hear this phenomenon. Repairing this problem means that you will have to track down the noise and shim the pipe. And take my word for it this is NOT normal. If it were the Plumbing Page would be overloaded with complaints.
Regards, Tom