We have a 1950s semi detached house that was built originally with 1 downpipe at the front of the property (my side at the end) and 1 downpipe at the back of the property (in the middle, my side), the front drains into the main sewer, the back drains into my garden (no soak away just literally onto the soil at the back of my property). We and our neighbours have both extended our properties (double storey extensions roughly 50% added onto size of the original house). My builders installed 2 extra downpipes on my property to allow rainwater to drain into new soakaways they dug on the front and back of my property for my new roof. Our next door neighbours have had no downpipes installed at all. To summarise I have 4 downpipes they have zero. My issue is that the extra volume of water now required to be drained when we have any rain now is overwhelming our shared downpipes and resulting in water cascading over my guttering near the downpipe which is roughly in the middle of the two properties (but on my bou dary) and resulting in my patio becoming flooded to the point its threatening to come into the house. Until their extension was built weve never had an issue with this in 6 years. I've raised it with them and they just said they think I've got moss blocking the pipe which we dont as we clean the gutters frequently and had only just done it. My question is at what point are the neighbours required to add a down pipe onto their guttering as the extra roof area is obviously overwhelming the system we have in place currently? I know that the old rules state that the guttering and downpipes were shared and that you have joint responsibility for the maintenance etc and that they have the right to use our downpipe but with them having added such a large extension surely this becomes void at some point or am I wrong? Also if it doesnt actually drain into a soakaway of some description then surely they should have one installed on their side shouldnt they? Any help would be appreciated as I'm trying to contact building control but they take months to respond at the moment as they are overwhelmed.