Author Topic: Need help identifying odd pipe pressure problem  (Read 2594 times)

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Vortechs

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Need help identifying odd pipe pressure problem
« on: February 09, 2017, 06:46:34 AM »
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.

 
« Last Edit: February 09, 2017, 06:54:40 AM by Vortechs »

DamonHD

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Re: Need help identifying odd pipe pressure problem
« Reply #1 on: February 09, 2017, 07:50:28 AM »
There's no air leaks in the pipework?

Rgds

Damon

Vortechs

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Re: Need help identifying odd pipe pressure problem
« Reply #2 on: February 09, 2017, 10:32:59 AM »
That what I initially suspected, but I've checked all the pipework and connectors multiple times now and cannot find anything wrong.


MattM

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Re: Need help identifying odd pipe pressure problem
« Reply #3 on: February 09, 2017, 10:34:31 AM »
Sounds like my well when sediment fills up the first stage filter screen.

Harold in CR

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Re: Need help identifying odd pipe pressure problem
« Reply #4 on: February 09, 2017, 12:10:36 PM »

 Is it possible for the unloaded gush of water to bypass the filter, but, can NOT bypass under load ?

mab

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Re: Need help identifying odd pipe pressure problem
« Reply #5 on: February 09, 2017, 01:19:57 PM »
does sound like a blockage to me - except the standing pressure shouldn't be lower. Assuming it isn't just the pressure gauge going flaky, the lower standing pressure would suggest a leak about 5psi's worth (i.e. 3-4m vertical) from the top.

camillitech

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Re: Need help identifying odd pipe pressure problem
« Reply #6 on: February 09, 2017, 01:55:44 PM »
Hi Vortechs,

does sound like a blocked screen to me. Regarding your air getting in the rises over a period of time, this happens on my system (900m of 90mm). What I did on mine at one problem spot was just drill a 2 or 3mm hole in the pipe at the highest point which worked just fine without any significant loss in output. However I got sick of people telling me I had a leak so fitted one of these http://www.javelinirrigation.co.uk/html/Turf_Products/turf_products/air_release_valves.htm using one of these https://www.pipestock.com/saddles-clamps/clamp-saddle-single it worked so well that I fitted a few more.

Good luck, Paul

Vortechs

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Re: Need help identifying odd pipe pressure problem
« Reply #7 on: February 09, 2017, 04:17:21 PM »
I've never had a partially blocked filter before so I wouldn't know what to expect.

A restriction at the filter could explain the delayed pressure. It's also possible there could still be some air trapped in a few high spots in the pipe that's not getting dragged out because the water's not moving fast enough when I run it through fully open. That would explain the 5 psi that I'm missing.

There's some dry weather forecast this week so I'll get some help and drain the pool so I can inspect the filter.

Thanks for all the replies.

MattM

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Re: Need help identifying odd pipe pressure problem
« Reply #8 on: February 09, 2017, 08:04:25 PM »
If it's sediment in the filter then it's permeable still to a degree, just the potential is greatly limited.

Vortechs

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Re: Need help identifying odd pipe pressure problem
« Reply #9 on: February 10, 2017, 10:48:16 AM »
It's probably gravel. The stream is on a rocky peninsula, the pool bottom is bedrock, anything smaller than gravel would just pass through the system.

I'll let you know what I find.

Vortechs

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Re: Need help identifying odd pipe pressure problem
« Reply #10 on: February 12, 2017, 10:13:03 AM »
It was mountain grasses that had clogged up the filter and caused it to implode.

Normally the dead grasses just rot down where they are, but we've had the driest winter anyone can remember, and they have blown into the stream and ended up in my filter.
 
I made a bigger stronger filter with larger surface area. The hydro is working great again now. Thank you all for your help.

DamonHD

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Re: Need help identifying odd pipe pressure problem
« Reply #11 on: February 12, 2017, 01:09:12 PM »
Glad you sorted it!

Rgds

Damon