I live in an older home (1940's) We've been dealing with a clogged sink. everytime you run water it would fill up. take approx. 15 minutes to drain..then, good to go. Finally got tired of this week. Used a CLR product for the drains...waited 15 minutes and the sink was unclogged. However, later that day, husband and daughter took showers....tub won't drain now. And to top it off....if you run water or cleaners in sink.....it backs up the tub drain. How can we unclog or do we need to get a plumber?