Hi Sezjane - I can help you there - ring a plumber who will save you a lot of heartache and will be able to do the job properly.  You may or may not be able to achieve what you want - but a proper plumber will tell you that.  They aren't free - but they are good value for money.  Or you could muck around yourself, it could end up costing you twice as much as you break things and cause havoc.