Grease traps and interceptors capture oils, greases, and other fatty deposits, so they don't enter your sanitary sewer system.
If the drain in your kitchen takes longer to empty, this is a sign that a clog is building, possibly further down in the gutter. A plunger may be able to pull out the impediment. You might also use a drain cleaner, baking soda, vinegar solution, and hot water to loosen and break up the clog.
Open the toilet tank and throw a few drops of food colouring into the water to see if your toilet leaks. Go again in 15 minutes to observe if the colour of the water inside the toilet bowl has changed. If the colour of the water has changed, your toilet leaks; however, if the water is still clear, there is no leak.
Rusty, blue, or green stains in the bathtub can be brought on by low pH or acid water, which is brought on by an abundance of carbon dioxide in the water supply.