How about pulling a vacuum on the pipes instead -- assuming that they can take the compressive forces of pulling a vacuum on the pipe. This will cause the water to evaporate relatively quickly -- assuming that you have a way of sealing the other end of the pipe.
Enjoy, DoN.
I'm sure that any pipes that can take an internal pressure of 50-80 psi can handle a vacuum without imploding. However, that would be a very large volume of water to evaporate. If you do try this I recommend watching a vacuum gauge as you pump down as you will get boiling and then freezing and you will see a plateau at 5-15 torr during boiling and evaporative cooling. Keep pumping until the pressure falls below maybe 5 torr (where the amount of ice starts to become large), and then vent the system to air and allow time for the ice to melt before you do another cycle.
Karl, I know you said that all the special risers and valves you need are not available in PVC, but how about using PVC pipe for the main runs and adapting to iron for all those fittings? When they rust out you can replace them but you won't have to dig up all the long runs of pipe, at least.
----- Regards, Carl Ijames
On 23 Apr 2010 01:34:17 GMT, the infamous "DoN. Nichols" scrawled the following:
Or a -hot- air blower down the pipe for a couple of days, then sealing it tight.
-- ...in order that a man may be happy, it is necessary that he should not only be capable of his work, but a good judge of his work. -- John Ruskin
Since the irrigation-pipe volume is around 20 cubic meters per km, running a hot air blower might be far more practical than either a compressor or a vacuum pump or a surplus dry nitrogen generator. I imagine the underground pipe length is between 100 and 1000m, for
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