I have water emerging into my Kitchen sink - Sometimes fills 3/4 of the bowl
*live in a flat on the top floor of a purpose built - 7 flats per floor
*Had a new kitchen installed 3yrs ago no issues since then
*the water coming up thru the kitchen sink is warm plus food particulars or cold & smells like washing machine
*i don't use my washing machine (lazy-Laudry!)
*don't have D/Washer
When the sink is full, i've undone the U bend pipe and released all the water (full bucket) - the U Bend is clean no waste in it
Sometimes the water will drain away or sit for approx 2hrs then drain away??
I have tried crystal soda plus water and its not draining as normal
I don't think i have a blockage but could a neighbour have installed a washing/dish washing machine and put the waste into my pipes????
i'm a little confused and would appreciate your help - please ask any qauestion that may help