advice re extending a toilet waste pipe

[Jules-and-Boo]

hi,

we're looking ta moving the toilet by approx 21-22ft, 6-7m. Basically moving the bathroom to an internal room (ie not at the back of the house) and extending the room to create a bedroom.

I understand the drop is 25mm per metre (more over 7m). Is there a maximum length that a waste extension can be? I've heard there is but not sure it's official? It is because of the volume of water /flush?

How much is it likely to cost?

Is there anyone that's had this done? I'm sure it's quite normal.

[alice]

did this but dropped the waste vertically down and met the waste pipe in the side angle.

[Jules-and-Boo]

it's the ground floor bathroom I'm moving, so needs to be horizontal (with drop)