So. I have a job coming up capping a dirt floor in a craw space with the customer not wanting any mess in the house yard etc. I run 3" system on a swing tube pump. My question is can I reverse air clean out back into the hopper with the cover shut? I'm planning on air input on the discharge end with a cheap nerf ball so I don't really care if the ball get's chopped up by the swing tube. Then drive off site to rinse out the hopper. Am I on the correct path? Thanks Crete Also I would be running the pump in reverse, forgot to say that.

Sounds like a great plan Terry! Take  a few photos : ) I've been thinking of back blowing , but i haven't tried it yet. I use a tub and plastic. Timing and dry pumping helps. Off site cleaning should be an extra 100 bucks? i hope.

Yes it will work you might want to tie down the lid just in case you didn't shut the air off fast enough. Depending how fair of a drive you need to make to wash you might want to suger the mud .

Pump will almost pull it back in reverse without the air, so be easy with air.  Be sure and leave it reversing while you have air on or it will blast lid.  Very little air is needed.  Once you pull reducers off back, shoot a few gallons of water backwards through s-tube while reversing to keep mud loose.  Drive slowly with hopper full of mud, it will jerk you into a tail spin due to the weight lifting up on tongue..i nearly learned this the hard way!!  Never crossed my mind, but I won't ever forget it now!  I liked this method of clean out so well that I used it ALL the time, even when dumping hopper on site.  A whole lot safer and contains mess very well.  

U may have to pump some mud back in the truck if u don't get it cut off soon enough. Put ur wad and air on the end and put her in reverse. Have ur helper sit on the lid. I do it lots, works every time.

we suck back without air , but I still normally tell the homeowner , contractor they either provide a washout spot or a washout bin , I try not to leave jobs with concrete in my hopper , way too much can happen while on the road.