On your question, I can say one thing - choose some plumber in Toronto and let him come to your new apartment and look at everything on the spot. It is also necessary to find out if there have been precedents with flooding of the first floors in this house before. As for plumbers, I advise you to call Pom Waterproofing https://www.pomwaterproofing.ca/back-water-valve-installation/. They are the best in town. Arrived quickly and very smart.