Boondock Camping

If you are out boondock camping, where do you go when you need to replenish water tanks and empty the black water? Also, What are some good guides for campgrounds in general? I came across https://www.ultimatecampgrounds.com/ in my searches. 

Regards to boondocking, national forests typically offer free, dispersed camping and we've taken advantage of this often. Google a national forest that you're interested in and then look for camping info. Dispersed camping details will be there. And the regular campgrounds are cheap, in the forests, even more so with the National Parks senior pass (if you are 62+). When we plan on boondocking we fill our fresh water tank all the way and dump our waste water tanks before heading out. This can last you maybe 2 weeks. Or we locate a nearby dump station and use as needed. We also use solar panels to charge the battery in the trailer. Have fun!