Would really appreciate any ideas on primeout on 20-25% downhill slope, 400ft-4in pipe 100ft 3in pipe 3in hose from there. Pea gravel 4000psi ,and I have 2 yds grout coming first. Thanks in  advance!

You should be good with two yards of grout and using steel there is no water loss maybe on the rubber hose pre wet it.

Put somthing in line to slow the slurry down so near the end it just dont coat the bottom of the line the idea is for it to push out a sponge or newspapper so it slicks the whole pipe somtimes down hill it will run to fast and just get the bottom half

Some guys will put a piece of plastic between the couplers with a little bit of an exposed area at the top to vent the displaced air.  This keeps the prime from becoming a runaway.

A 'rabbit' of soggy newspaper or soft sponge helps keep the prime back too.

Another issue to be concerned with is the effect of gravity, unlees you have some method of holding back the flow, you will never truly shut off the flow when pumping is stopped, it will keep oozing out.

A 'camel's hump' (new term recently) will help as will creating a loop with hose, or a couple hard 90's on the way down the hill too.

Pumpjocky said it all. I run a ball valve pump and it will slowly suck the hopper dry also.

From my lessons learned files.

Look at the basic mechanics on the job.This is not a long push but doable very easy.I always used a piece of old spounge cut to fit,but in this case your reducing to 3" I feel plastic would work best.With 2 yds grout is a little over kill but oh well.I found long down hill pushes a richer mix a little dryer helped,mud won't seperate so easy.We had good communications with pump/discharge (radio) and they kinked the hose to stop run away mud.Don't pump to fast,just enough to keep things flowing at required rate.Good old common sense and patience pays off here.

1,000' - 1,500' 4" pushes up/downhill were common at the ski areas and it worked every time.Let us know how it went,for my "stranger than fiction files".

I will agree with many. The sponge technique will work just fine in your case. Even though it may be 3", it will keep the prime from running out and that's all you need

go up to wal-mart and pick up some of them big squishy foam balls. Soak them in oil for 24 hours, push the one plug inside of the pipe, install a 90 vertically up on your pump side, add one bucket of slurry. Push another ball in and add another bucket of slurry. Thats What we did on the Kinzua bridge job, and as far as priming and first truck everything went spectacular. Besides the fact that we ran a go-devil in behind the slurry / ball / oil mix, and we were at an 87% grade instead of 20. You could always go with bentonite (clay), but it will have a harder time sealing the clamp gaskets. When you go to clean up what are you going to do? Are you going to disconnect the 3 inch, clean it out and run a go-devil through the 4 inch? Best wishes ~ Brandon

the camels hump pump jockey was talking about is what we used on the kinzua bridge job. Your only going down a 20-25% grade though, so I'm not sure if you'de need that kinda setup though. Really you should only need about a 1/2 yard of concrete to get the job done right.