Next door but two had some sort of work done that involved plumbing.
They seem to have plumbed something in so that dirty water flows into their drain pipe, ending up on the road and in the rainwater drain. We often see a fast flow of dirty or soapy water flowing down the road, when there's no rain. It flows past my house into a drain.
AIBU to think they should have plumbed it in properly, and I shouldn't have their mucky water flowing outside my house.