Hi everyone - I checked with the author to clarify this passage in our Beginner's Guide to RV Travel in the 2014 Good Sam RV Travel Guide. We definitely didn't adequately explain the process involved in emptying holding tanks on pages 56 and 57.
We should have specified that that the black tank dump valve should be opened only after the black tank is adequately full. Please consult this excerpt from an article on our Good Sam Camping blog that addresses the concerns posted.
http://blog.goodsamcamping.com/2014/01/a-holding-tank-primer/
I hope I've answered the questions raised and my apologies I didn't get back to this post sooner.
Thank you for your understanding and be assured I will answer your queries as soon as possible whenever you post - Sundays and however strange included :)
Kind regards,
Ellen
Sr Product & Marketing Manager