IS IT BETTER TO HAVE SOME 4" PIPE IN THE BEGINING BFORE REDUCING TO 3" HOSE,  AND DOES IT HELP RELEAVE STRAIN ON THE PUMPS OUTPUT?

"Just my opinion"

I would reduce and get it over with. Easier to find & correct a problem. ;~)

I second that.

I think Bob  nailed it but depends about the mix and what application. Piston heads water content and so on.

here we run 100 feet maximum when pumping 3/4 rock its actually better to run 4 inch pipe. on long runs we run 4 inch pipe then reduce down to 3 inch at the last 100 feet and using smaller line does affect volume and put ware on pump theres another company here that runs 300 ft of 3 inch hoses i see there pump struggling to push that out at full output then the hosses get worned out from rubbing on ground. for us 100 ft works out.

I don't get the logic.

If the mix is a dog you MAY be able to get it to organize its self once. But to ask it to re-organize after you have pumped for some length...... I don't believe that would be to your advantage.

Most concrete will, once situated in a hose or pipe, pump until you:

1. ask it to reduce further

2. run out of piston face pressure

The 'reduce it now' school of thought is; find out what you are dealing with where the pump has the most ability to deal with it. And if the mix is a cream-puff...... well, I still feel the same way. I am learning every day and am more than happy to entertain another logical reason for doing it another way. ;~)

if it is system you are doing i use to years ago have a 4" reducer that was 5 feet long, nice for crappy mixes sometimes that slow transition does the trick.

THE REASON I ASKED WAS MY OLD SHWING 1000 PUMP WOULD GET STUCK AT THE 5" TO 4" REDUCER WITH HARSHER MIXES, SO I WOULD HAVE TO REVERSE THE PUMP A LITTLE TO GET IT TO GO AGAIN, AND MY REDUCERS AND ELBOWS ARE FAIRLY NEW, SOMEONE MENTIONED RUNNING YHR 4" INCH AHEAD OF THE 3".  I HAVEN'T TRIED IT YET BUT I WILL AND I'LL SOLVE THIS MYSTERY AND LET YOU GUYS KNOW. BY THE WAY LOVE ALL THE INFO ON THIS WEBSITE. (ALOHA!!!)                                          

Good point!

I know that folks run 4" pipe and 3.5" or 3" hose at the end. I think that this is done for economy. They own the 4" pipe and the customer wants 3" hose; and they are too smart to run all hose. And oh by the way, they don't own the 3" pipe.

Economic considerations are very important in the pump bizz; it is hard to make $$$.

If you are in the position to buy and use pipe the same diamater as your discharge hose, do it; you will have far fewer problems; especially restarting after a delay. You may reverse a problem out of a reducer at the pump but will be hard pressed to accomplish that trick with a 'downstream' reduction. ;~)

Years ago we had an old dinasour 36m schwing everything on it was wore out so we replaced all the pipe with 4" and they used it just for icf pours, worked out niceley and made good money with something you woulod not want to send to do a 300 yd pour.