Slow flush toilet with slow drain bathroom sink
I am hoping that someone can offer a suggestion to solve my problem. We recently purchased an 8 year old townhouse. We have a double vanity (2 sinks), a toilet, a free standing shower, and a jacuzzi in our master bath.
I have a two fold problem which I believe are related. The toilet last week started to flush very slowly, which eventually led it to not flushing at all. So, I removed all the water (using gloves, etc - not fun) and using a plunger got the toilet to flush slowly. So now it fills the bowl and than slowly empties. I bought an auger (3 foot) and did that a few times, as well as buying Drano Professional Prevention and have done that a few days in a row per instructions. I also bought this professional strength powder that has enzymes and did that for 3 days. All of this based on Home Depot's recommendations. I've also filled the bowl, flushing it with hot water, and the flushing did improve a bit, but not completely.
I also noticed that the sink closest to the toilet drains completely fine until the water has run for about 5 minutes and then all of a sudden it starts to back up and then drains very slowly. So I also plunged it (different plunger), used drano, and hot water flushes, but it still does the slow drain after 5 minutes.
The other sink, shower, and jacuzzi I should mention have no issues at all. I would've thought at least the other sink would have a slow drain problem, but that is not the case.
So I assume the toilet and sink share the drain somewhere and this is related. Am I correct to assume there is a partial blockage somewhere down the line or could this be a venting problem? How do I determine if it is a venting problem.
The master bath is on the 2nd floor, and the basement is finished and we are on city sewer.
My next step is to call a plumber, but was hoping I could get some suggestions.
Thank you