Hi Allan,
"In your first post you said you ran a siphon for two months and you believed the subsequent loss of siphon was caused by lower areas, can you elaborate on this please. Provided there is a continual slope in the first section after the Loch wall at least until the elevation is several meters lower than Loch water level plus the number of meters it is lifting the water, then any slight rise should not stop the siphon. That said if the outlet was restricted and all air was not purged out of the line initially then said air will find it's way up the pipe and break your siphon."
To asses the viability Allan I ran a siphon just over the lip of the loch for a couple of months to see how much I could extract without lowering the level. As it ran perfectly the whole time I thought that I was 'onto a winner'. However the pipe I used was 6m long lengths of PVC ducting cemented together and the only valve in the system was at the outlet end. I simply got the siphon going by opening the valve, submerging the whole pipe in the loch, then closing the valve whilst I dragged the pipe over the hill. I use the word simply as in simpler than trying to fill the pipe up with mouthfuls of water
Obviously now I have all the valves, joints, different size pipe and extra hills to climb it's a little more complex than I'd envisaged
"From what I can see on your blog I believe you could establish and maintain a siphon, when priming with your trusty Honda how have you stopped all the priming water going out the filter end?"
Valve B in Hugh's diagram
"If it was my project and I could not economically or practically dig that first section of pipe in I would......
1) Not tee in a priming valve at the high point, I would have it teed in near the filter such that it would be under water in service, say a meter or two away (reason for small distance will be evident when you finally place the filter in the water).
2) Pull the strainer out, connect trusty Honda and fill the line with the bottom closed off, have some wine and cheese on hand and wait for the line to fill.
3) Once full keep the strainer elevated, go home for the night have another bottle of red, return in the morning (in the intervening time any entrained air will have made its way out the top, this goes to my point in an above paragraph) Start trusty Honda and with it running lower the strainer into the water, go to the lower end and open the valve, return to the top and shut off the priming valve then stop trusty Honda and disconnect.
4) I would nevert fully close off the lower end, instead I would divert the water to dump, this will ensure that the siphon is not lost if there is any slight air ingress somewhere along the pipe.
5) If possible I would transmit the power as AC at full cable voltage utilizing transformers at each end. In my past life I had such a connection some 800M with 4mm sq cable which was quite happy transferring 3Kw with acceptable voltage drop."
All points noted, especially the digging in if possible and underwater valves/connections plus I'll try and increase the first few meters of 63mm pipe to 90mm as I feel that this is creating more negative pressure.
However AC is out as the turbine is on its way from New Zealand as we speak
Thanks, Paul