How long after whelping can my dam go for a quick dip in our swimming pool?

Wouldn't recommend it. The chlorine would still be present on the dog's nipples and it may make the puppies sick. You would have to completely bathe the dog before she went to her puppies . The chlorine smell alone could affect them. Get a kiddie pool for her with only fresh water, but she will need to be completely dry before returnng to the puppies.