Okay, here is a little map of High Farm, where I work. The point on it is a field, which according to Google Earth is 30m below the level of the farm in altitude. The point is at the approximate position of a liquid manure hydrant.
So, attached to these hydrants are sprayers, like these two:
and attached to the other end is a pump dipped in the liquid manure tank. For the past couple of months it has been draining out about 120000 litres of liquid manure… Or about that… onto the fields. The tank is now empty, and with winter here, and frost on the way, we need to drain the system and bring everything in, which was my job (I stupidly rejected the offer of Tom doing that and I doing the pigs….). So, to begin with the pump went into the moors water storage tank, and was switched on, this pressurised the top with fresh water, which we let out through two sprayers in the top fields. To drain the system the lower hydrant needed to be opened. Figuring that the two sprayers and the distance down hill to the hydrant, I thought there would be at least a second between opening the hydrant tap and the liquid coming out.
The hydrant is designed like this. There is a hole dug in the ground, about half a metre deep, with a pipe coming up through it. At the bottom of the hole is the tap as well to open the flow. To get to the tap you need to reach down, and in doing so your face passes in front of the hydrant.
My calculations of how long it would take the liquid manure to travel down to the hydrant, and the pressure drop from the 2nd hydrant open were not exactly spot on….. I got the full force of the pump, 30 metres of gravitational potential energy and about 10L of liquid manure squarely in the face. Oh the life of a farmer.
Still, could be worse… At least there was running water in the hosepipe to wash everything in Oh 4 degrees of temperature outside too.. Chilly when you’re wet…