My sister recently moved to an apartment in Velachery,Chennai.Her house is in second floor.From day one she is facing two kinds of problems. 1.Heavy bad odor from the attached bathrooms eventually spreading throughout the house when the windows are closed. 2.Swarm of small flies coming through the drain hole in bathroom.She has fixed a mosquito net in bathroom ventilators.So,flies are not coming thru them. So,far she has used mortein,good knight liquids ,hit spray,napthalene balls..But no effect. I suggested pursue,an Amway product meant for germ killing.She sprayed it all over the bathroom tiles.Now, the flies avoid the wall tiles and sit all over the bathroom ceiling. Regarding the smell,many times plumbers visited and cleaned the drain pipes, but in vain.She has to find another house again if the problems are not solved. Please,suggest any ideas.