Dawn does really unclog drains, but Dawn dish soap can only unclog and clear out minor clogs and partial clogs that are caused by oil or grease.
Dawn dish soap, will not clear out any serious drain blockages like food scraps, tree roots, hair, toilet paper etc.
Dawn dish soap is a highly effective degreaser, so it can break down film and light oily residues that build up along the inside of drain pipes.
And when Dawn dish soap is mixed with very hot water, the surfactants in the soap loosen the grease up and help to wash it down the drain.
The Dawn dish soap can also act as a lubricant in toilets to help organic waste pass through the trap more easily.
Although if your sink or bathtub is backed up completely with standing water, pouring Dawn dish soap down the drain is not gonna work.
Dawn dish soap lacks corrosive power as it's formulated to be gentle enough to use on hands and so Dawn dish soap cannot dissolve hair, wet wipes or any fibrous food particles.
And sometimes Dawn dish soap can worsen the clog, as dumping heavy amounts of dish soap including Dawn dish soap into a fully stopped up drain pipe can coat the plumbing trap.
And the dense soap can also act like glute and cause any new debris that enters the pipes to stick to the blockage and make it denser.
To use Dawn dish soap for slow drains, allow the water to drain completely and then pour 2 to 3 tablespoons of Dawn directly down the drain opening.
Then give the soap 10 to 15 minutes to break into the oil or film.
And then run hot tap water down the drain for a minute or two to flush out the emulsified grime.
In some cases the trap may be clogged and removing the trap and physically cleaning it can often get a drain in a sink going quickly.
If the drain is fully clogged then you will need to try a plunger first or a plumbers snake.
For bathroom sinks and showers, using a cheap, barbed plastic drain snake is highly effective at catching and pulling out dense clumps of hair.
And plungers are very effective, especially for toilets, but can also be used on kitchen sinks, showers, bathroom sinks and tubs.
However always use a separate plunger for your sinks than you do for your toilet to avoid cross contamination.
A hand cranked steel cable drain snake can also be fed directly down into the P trap to punch through tough food or organic blockages.