I don't know anything about plumbing and have just moved into my first rented house. Underneath the kitchen sink leaks every time we use washing up liquid, but not when we only run water. It's coming out of an open part that I've taken a photo of. There's a dish washer that we don't use that came with the house that's attached to the back of the pipes by the grey hose that's in the background of the image. We don't have a washing machine installed yet (it's coming on Tuesday), but there's a gap where it goes next to the sink so is it something to do with not having one?