Hi
I have an issue with my kitchen sink. I've tried using a snake and other unblocking material but nothing is working. Basically, if for example I pour a large amount of water down the sink in one go, it flows back up and comes out what I believe is the overflow pipe? I think water is sitting in the ubend which is backing up and causing the water to spit out elsewhere. It's coming out of the blue topped pipe on the left, see picture. This blue top is not screwed in FYI, it just sits in the screw bit and into the pipe. I'm not sure if it's always been like this...? Any help appreciated. Thanks.