Hi. When my tub drain gets slow - about every 2-3 months I put some GLUG into the drain and that usually does the job. A plumber told my parents never to use strong chemicals but use BIO-CLEAN instead. I tried it and it didn't work so I used the GLUG and got the drain working. Then I added BIO-CLEAN to the drain for several days and then monthly after that. The tub drained well for about 2 months then slowed down again. I added the BIO_CLEAN for 4 days in a row - leaving the tub to not be used for 24 hours and also going away for a weekend and no results. Showers are extremely quick so I don't have to stand in undrained water. Any suggestions? thanks!