Is there a laundry (either service or self-service) near the Hilton Mainz City Hotel?
A 5 minutes walk up Gaustrasse and at Hauptbahnhof (main station) are laundry services. The next self service must be the one at the corner Gärtnerstrasse / Kaiserstrasse, less than 10 minutes to walk.
I went to the Hauptbahnhof but it is not really a full laundry service. They only accept certain items (for example, pants and shirts; they do not accept underwear and socks). It is very expensive and they charge by the piece--it costs as much to launder 2 pairs of pants as it does at home for a regular-size load of clothes. Also, it takes 3 days for this service to finish the clothes. So it is not a good choice, and I could not find any other laundry service where I could drop off clothes. Luckily, my daughter has a washer and dryer in the building where she is staying temporarily, so I have been using that.
There is a difference between a "Waschsalon" (self service laundromat) and a "Reinigung" (dry cleaner). Freedshop describes the latter.
I have never heard of a laundry shop where one could simply drop ALL clothing incl socks and underwear. I doubt such a service exists at all in Germany, to be honest. That’s what self-service laundries are for and I had one close to Hauptbahnhof mentioned in my reply. Business travelers would use their hotel‘s service - which is very expensive, of course.
I do understand the difference between the type of service in the train station and the self-service laundromat. The reason I asked the question originally is that I did not expect to have time to spend hours in a self-service laundromat at least three times during the trip, so I was hoping to find a drop-off service like I have used in other places we have traveled. The reason I thought the service in the train station might be what I was looking for is that I asked at the tourist office if they knew of any drop-off laundry services, and that was their only suggestion.
Anyway, I was able to do the laundry in my daughter's building while taking care of her baby. But I think it will be useful to other visitors staying more than a couple of weeks to know that self-service laundry is the only practical option, considering wait time and price, and that you need to understand German to read the instructions in the laundromat.