I have a grout job coming up that will need grout. I have a tkb 45 putz going through 2.5" hose. Is there any sack limitations or is just a 4000 grout good enough. This will be pumped really wet also.

If it really wet 3,000 will work,but 4,000 you want know you are pumping almost like butter.

do not get 3000 lb really wet it will seperate, 4000 lb if its stacking up in the chute add some water but wait until its mixed. fibermesh is fine. i have a throdule servo on it because the driver will keep filling even though you stop pumping. the book says that the vibration will seperate the mud in two minutes. tkb-30 lots of power. 

you will be fine with 4000, if you are looking for a bag, I would say 6  to a 9 bag and you be fine.  if its grout and its mixed you wont sep.  but if you do I just stop the engine while your not pumping. you should be able to pump as wet as you want

Do you have to prime your line with slisk pac or something?