I have a question:

 

If you have a 100m loop of water (in a water pipe)  in a sealed circulating loop (with no air).......

 

If said circuit is going uphill (but of course what goes up must go down!) rather than level. Does it require more energy to circulate? In other words does it require a bigger pump?

 

 

No It will syphon over the top bit.

No - the falling water will create pressure that will be equal to the force required to lift the water ... 

That's why pumps are actually referred to as 'circulators' . 

Thanks guys. I had a minor panic moment after we started to dig the geothermal trench downhill which wasn't the original plan!