The Valtera thing looks like the way to go, now that you already have a clog.  I've heard of people trying to avoid any TP in the tank, but, in my opinion, that's nuts!  Why have a camper with a toilet if you're afraid to use it!  (To each his or her own, I'm just saying no TP in the toilet is like, I dunno, no gas in your car because it smells bad.)  Anyway, I've never really had a problem with our black water tank.  I think using more water to flush than you might think necessary and some kind of chemicals will keep you out of trouble.  Extra liquid more than anything is the best thing you can do.  I always try to add as much water to the black tank as possible before heading for the dump station.  Even a short trip in the campground to the dump station will stir things up pretty well.

TT 

We've used a reverse flush valve like the Valera and it is a good way to clean the tank.  In fact, I used a wand, ice, and the reverse flush all in a futile effort to clean the crud off the sensors for the tank level monitor.  

Our practice is to try to avoid the use of any tp in the tank.  Visits to the campground latrine are a much better way to avoid accumulation of solid matter, though that's not always possible.  For liquid elimination, it's really not a big deal to put the used tp into a little discrete plastic bag and throw it in the trash.  Obviously, for solid elimination, it gets a little delicate putting the tp into a bag, though in many countries with iffy sewer systems, it's common not to put tp into the toilet.  

Bottom line, using RV tp and limiting the quantities will go a long way to avoiding clogged tank drains.

Just stating a truth.. not trying to get anyone in trouble.. Hopefully, with new campers, someone explained to them the difference in camper vs home plumbing..

BTW, they make a "wand" that hooks to a hose, and goes down through the toilet, that may be able to get a powerful spray into the needed area..

Various Wands like this..

ESP. young females.

I agree that you probably have a giant wad of TP or something blocking the discharge pipe. Using the Valtera thing would allow you to blow the wad back into the tank. Then give another try. Might take several tries to get the wad backed out and broken up, but there you are.

I've found that some people use WAY more TP than they actually need...

If I understand it, the advantage of the one that I like is that it has a valve that enables you to fill the black tank and then dump it when you are ready.

I use one very similar to this one.  So far no complaints.

https://www.etrailer.com/RV-Sewer/Valterra/F02-4110.html

Good luck

I don't know what you tried that barely loosened 'stuff' up but ...

My suggestion is to get something like this - 

http://www.valterra.com/product/flush-king-reverse-rv-flush-valve-boxed/

Fear no plugs! - "Go ahead, poop, make my day"

On a 171, and probably others, the black water drain is very low. Whatever you get, make sure it fits. 

Wands are ok, but messy.

Good luck

Last weekend W & I took 3 grandkids with us and they helped fill tank faster than I expected. When I tried to dump it ....well, it was constipated. So much for the least toxic tablets.  Borrowed someone's elbow with back flush and that barely loosened things up.

Tried some heavy duty (no pun intended) camper black tank chemical (double dosed it). Drove home full hoping the chemical and bouncing on the road trip would help.  Tried to dump it today.....only minimal relief!  Added another dose of the potent camper chemical and will check tomorrow.

Recommendations appreciated....my 179 needs some relief...which will make me very happy too.  When it finally releases I will use the black tank flush, using it now might be a bit ugly. Can the tank be snaked carefully? I can't image being at the low end, which is probably where it is blocked, when it is broken up and releases....or maybe I can imagine.....I can't run as fast as I used to....  HELP