Your dog will likely drink around 30-50ml per kg or 15-25 ml per lb of body weight per day. However, there is often variation amongst individuals depending on the water content in their food and exercise.
Based on this rule, a 20lb/10kg dog will drink about 300-500ml per day. If your dog is consistently drinking 80-100ml per kg per day or more, then this may be a sign of polydipsia (drinking too much water). Polydipsia can suggest there is a health problem to address.
If you are concerned, measure your dog’s water intake by filling up their water bowl with a set amount of water and see how much is left after 24 hours. The best thing is to do this for a few days in a row then average the result, so there is less of a daily variation.
Of course, if your dog is eating well and seems otherwise healthy, it is very unlikely that there is an issue.