I know nothing about plumbing…
Under sink in utility room there is a slightly damp fitting which is dripping a little. It’s grey plastic push fit stuff, ther is a T piece which comes upwards off a horizontal hot pipe up to a vertical which runs up to tap. Push fit methinks as cheapo newish house and it seems to comprise, from the top, grey pipe, which runs into a black end/washer, then down into an inverted bowl shaped alloy/stainless fiting, which joins the T piece and next bit of pipe. water is welling slightly at the base of teh grey vertical pipe where it goes into teh black ring thing and metal bit. I gave it a wiggle and it stopped – leave alone and keep eye on or is there a way of tightening – I guess either push it all together to compress, or pull pipe back to tighen end against something inside ?
sorry for bad description !!