There is a smell coming from both the sink and waste outlets in the bathroom. Caustic Soda has been flushed through and the outside drain has also been flushed. What can be done to eliminate smell?

For hathroom sink smells The first thing you should do is pull the stopper and shine a light down the drain. You will see a small rod down there. Hair can catch and build up on this rod and impede the flow. Take and hook any hair that may be down there.. Afterward flush the drain with hot water. Place a hook on a pierce of wire and see if you can fish out any hair in the tub drain. Let me know if you need more.. tom