sink drainage

[butch4ng]

i want to move my sink and WC overflow drain from above the floor to below the floor but the outlet to the outside is higher then the floor.

is their a problem with moving the drain pipes under the floor the sloping the up through the wall or will their be water in the pipe all the time?

 

[Expertboy]

Water wont run uphill, not a good idea. There are now syphons with internal overflows, why not just replace that and take away the overflow completely.