I need help identifying the cause of an odd pipe pressure problem. About a week ago I noticed the pipe pressure on my micro hydro was down a little. This occasionally happens due to air bubbles collecting in the rises, but is easily cleared by running the pipe through full bore for a few minutes. It's an old system that's been running for 13 years, so I'm well used to all it's quirks.
This time however it only made it worse until I had no pressure at all. I can still run the pipe at full bore at it's usual speed, no air comes out the pipe but when I shut if off there is 0 psi and it will gradually climb to about 45 psi over a about a minute. It's normal standing pressure is around 50 psi. Running pressure 45psi. The hydro will run as normal but with a pressure of about 40 psi.
I've spent the last 5 days trying to figure it out but I still none the wiser. I've walked the whole 250 meters of pipe and checked and tightened the 4 connectors. The filter is very difficult to get at in the winter when the stream is in flood so I've not been able to check it thoroughly but what I can see of it looks normal. Could these symptoms be caused by a partially blocked filter? The pipe fully open at the bottom end appears to run through as fast as normal.
Pipe 3" / 75mm
length 820 ft. / 250M
Head 130 ft. / 40M
Pelton Wheel with 13.5mm nozzle.