Pumping concrete downhill is possible, you just need to hire the right concrete contractor for the job!
1) As your pump surges, the hoses get stretched downhill and if you have a clog, it’s hard to drag your heavy hoses uphill to reconnect them when you take them apart to undo your clog.
2) You are more likely to have clogs because when you are pumping downhill. The water and cement separate from the aggregate (the sand and gravel) and that is called sand-packing. When sand-packing occurs, you will have an area in your hose where it’s just pure sand and gravel and no cement at all. You cannot pump sand or rock by itself.
It is possible to pump downhill! When you are pumping downhill, you need to put a loop in your hose and stake a clamp to the ground. The loop will also help with sand-packing. Sand-packing is mainly a problem when you start pumping or when you stop pumping. Once you get primed out, sand-packing isn’t a big deal as long as you continue pumping.
To prevent sand-packing, pump to the end of one hose and when concrete comes out the end of that hose, add an additional hose and repeat that process until you work the concrete out the end of all of your hoses.