This last summer we did a 700 ft line job (4 in) across a bridge (nasty bridge mix) what I found worked good was a yard of slurry from the plant, however you could probably get by with half a yard. As far as cleaning out that much system I would just use the apropriate air aplications.Jamie

Slurry is the only way to go. I like getting water in front of it first. I have also blown out up to 300 foot of line with my hydraulic water pump, but air is the easier way. Make sure she is tied down

Bentonite is an effective option however you should take into consideration that if you do not get all of it outside the form it will compromise the strength of the concrete.Jamie

Thanks for the input. How about cleaning with air? How exactly does that work? How do you hook air up to line? Is it safe? Do you push a ball or something through?

Having soem two way radios sure helps when blowing out with air. One guy on the blowout cap and another guy following the rabbit through the pipe if possibe to make sure it does not go too fast.And of course have everyone out of the way of the blowout area.

Dave, #1 if you are not anACPA member, JOIN !!!After you join you can ask for the safety video onCleaning out system it will answer all of your questions. ;)