Black water flush valve 'Out of Warranty'

Altho the valve won't destroy if it's put in wrong, it just won't work.  http://bay172.mail.live.com/mail/ViewOfficePreview.aspx?messageid=mgRrtEsfH05RGUKAAeC8wHzg2&folderid=flinbox&attindex=0&cp=-1&attdepth=0&n=70562650

So, I bought an old-fashioned 90 degree elbow, figuring to add it and 'straighten out' the current 90 degree bend of my installation. 

My Question - It's for a regular house, metal and heavy, should I wait for a non-metallic one?? http://www.walmart.com/ip/44692995?wmlspartner=wlpa&selectedSellerId=83&adid=22222222227031995551&wl0=&wl1=g&wl2=c&wl3=61117744736&wl4=&wl5=pla&wl6=108512472776&veh=sem 

I eagerly await your responses.

Ok, I put the valve back in, facing the correct way now, with just a little crimping of the 'outflow' hose because of the changed geometry of the replaced valve position, but not so much it couldn't be pinched opened by my fingers.

So, I just turned on the water, no flow, at least by ear, and the backed up water pressure was sufficient to blow out the little screen in the entrance hole when I removed the hose (and drench me, of course). 

So I know it's still plugged.

I presume the blockage is between the outside of the trailer and the valve because I felt no vibration in the inflow or outflow hoses when I was jiggling the valve up and down to ensure that there was no crimping, and also there was no leakage anywhere, which considering my nonexistent plumbing skills, I totally expected.

Now, I really like my R-Pod but this makes me suspect that the fumble-fingered, ignorant, #$**%$# of a trainee who put in my valve also did something else to cause me this trouble. 

   ?Any suggestions as to how to trouble shoot this???

I WISH that Forest River had a better manual that, among others, described the use of the flush. As a rank 'Newbie' I had NO IDEA how useful it is. 

I loaded the black tank with ice, detergent and Calgon water softener and spent some time on a couple of nice West Virginia roads (Twisty, steep and rough) but I'm still blocked. Until it clears with repeated treatments, from now on each time I dump, I'm putting a couple of gallons of water down the toilet to mimic the effect of the flush, and a 'Johnny Chock' may be in my future.