Whether a laundromat can deny the use of their dryers to customers who haven't washed their clothes there can vary depending on the specific policies of the laundromat. Different laundromats may have different rules and guidelines regarding the use of their facilities.
Some laundromats may require customers to use their washers before using the dryers, as this is how they generate revenue and cover their operating costs. If you're using the washing machine, they can reasonably expect you to use their dryers as well. In such cases, customers who have only hand-washed their clothes or used their own washer might not be allowed to use the laundromat's dryers.
On the other hand, some laundromats may allow customers to use their dryers independently of whether they used the washing machines there or not. This approach is more customer-friendly and may accommodate those who prefer to hand wash or use their own washing machines.
The best way to find out the specific policy of a particular laundromat is to check their posted rules or inquire with the staff. If you have unique laundry needs, such as hand washing or using only the dryer, it's a good idea to look for laundromats that explicitly state they allow such flexibility in their usage policies.
If you encounter a laundromat that restricts dryer usage to only those who washed their clothes in their machines and you prefer not to use their washers, you might need to seek an alternative laundromat or explore other options for drying your clothes, such as air drying them at home or finding another nearby facility that offers dryer-only services.