How much water head do users of Phil's Sparger (spinny sparger) find necessary to drive it successfully ?
When I first used mine I found that it kept stalling and so increased the water head height so that when there's minimum water level in the HLT there's still about a metre of head. This means I use about a metre's worth of tubing to connect the HLT to the sparger.
I'm now wondering if I can actually get away with a much reduced head high *if* I reduce the length of tubing accordingly as I believe the water resistance generated by the length of tubing is actually quite a significant factor. When I initially had the stalling problems I was still using about a metres worth of tubing so the water from the HLT had to overcome the tubing resistance of that length presumably resulting in reduced flow rate and sparger stall. Another benefit of reducing the tube length would be a reduction in heat loss from the HLT to the sparger.
Comments anyone ?
Spinny sparger
Here's my set up:

I use 12" of tubing & the tap is about 8" above the top of the Spinny Sparger. With the down tube of the Spinny Sparger, that's about 14" of head from spinning arm to the tap. The water boiler then had around 15/20 litres of water in it at the start of sparge.
I had to add 6 clothes pegs to the water tubing to slow the flow rate down at the start of sparge, as it was trying to go into auto rotation. With the clothes pegs, I then got a steady rotation probably around the speed of DaaB's 6" mpeg.
As the level of head water in the boiler decreased, I reduced the clothes peg restriction system down to 3 pegs when the boiler was pretty much empty, to maintain a slow rotation.
Unfortunately, my boiler tap is either fully open or closed, I can't control the flow rate with it.

I use 12" of tubing & the tap is about 8" above the top of the Spinny Sparger. With the down tube of the Spinny Sparger, that's about 14" of head from spinning arm to the tap. The water boiler then had around 15/20 litres of water in it at the start of sparge.
I had to add 6 clothes pegs to the water tubing to slow the flow rate down at the start of sparge, as it was trying to go into auto rotation. With the clothes pegs, I then got a steady rotation probably around the speed of DaaB's 6" mpeg.
As the level of head water in the boiler decreased, I reduced the clothes peg restriction system down to 3 pegs when the boiler was pretty much empty, to maintain a slow rotation.
Unfortunately, my boiler tap is either fully open or closed, I can't control the flow rate with it.