Inner "sleeve" inside drain ?

[bobturnip]

Our kitchen drain has blocked and overflowed. I have spent a full day rooting around outside trying to get a rod into the drain chamber, without any success at finding the hole - only to realise that there's a loose plastic inner sleeve inside - a kind of pipe section fitted snugly inside the drain that just slides up and down, and is covering the hole. It was gummed up with gunk, and on freeing it, the drain began to empty.

I am hoping this makes sense to someone. Excuse my ignorance, but what is that thing called ? And what is it for ? Can I just remove it, or is there a valauable purpose to it? Seems like it might be more a hindrance than a help (?)

Thanks in advance.

 

[ReJect]

Some gulleys have a inner pipe dipped down into their chamber to make a trap so no sewer gases escape, rather than the usual U bend type of gulley.
Not sure if that is what you have

 

[Nige F]

? And what is it for ? Can I just remove it, or is there a valauable purpose to it? Seems like it might be more a hindrance than a help (?)

Thanks in advance.

You can remove it for access to the drain then put it back = if left out it will allow sewer gasses escape