The house next door is rented out. Every few years new tenants move in. I have just noticed today that one of their downpipes (one within 12 inches of my property) is not connected to a drain but finishes about 2 feet above ground and just drains into the soil at the base of their house. When there is torrential rain, like today, the ground under their drainpipe cannot cope with the rainwater and becomes so flooded that the water comes through my garden wall and onto my property. Once on my property I have a drain that carries my own rainwater away and it looks as if all their rainwater is also going down my drain. The thing I'm not happy about is that the owner of the property has never cleaned his gutters in over 20 years so no doubt all that crap is going down my drains with their water. I've recently spent a fortune getting all my drains replaced, I don't want any more problems with them.
The tenants are non-English speaking so there's no point speaking to them. Also the property owner lives a long distance away and I believe he does not use a letting agency to let his property so I'm not sure how to contact him.
Do you think their rainwater is going to cause a problem or am I overreacting?