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Thread: Air locking 4 inch pipe
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26-04-2020, 12:05 AM #1
Air locking 4 inch pipe
Hi
It was never going to be perfect but when I ran the 4" pipe to my sieve there was a downward turn. It runs fine but gradually seems to build up air inside.
Now the question am I brave enough to drill a small vent in the high spot and tap the plastic to screw in a fitting so I can attach a small bit of airline to above water surface height to allow air to vent?
Anyone else had this
Andy
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26-04-2020, 01:10 AM #2
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26-04-2020, 07:36 AM #3
I don't think it would draw air in as the flow is very slow.....however its an unknown. I could put just a small air valve in it to close it off when its not needed i suppose.
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26-04-2020, 07:53 AM #4
You could do that with a valve, then simply switch off the pump and vent any air every 6 months? Only issue is if any waste blocks the air valve on the pipe side (also any biofilm)?
A larger pipe diameter would probably be ok - vertical, and put a screw top on it. At rest the water would fill up the vertical pipe. In operation the pipe would take up any air like a reservoir but the cap stops any suction of air. Then simply unscrew the cap when servicing and the pump off - the water pressure will expel the air and retighten the cap again.
Although flow rate isn't high pressure may be higher - so a tap into the pipe may want a strap around it - something like this? https://www.plumbingsupply.com/hot-w...-pvc-pipe.html
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Andymadd Thanked / Liked this Post
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26-04-2020, 08:13 AM #5
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26-04-2020, 09:01 AM #6
If it was me in the same situation i would drill and tap a 1/2" BSP thread and then tap in a valve, then a length of clear pipe and then another valve, the reason for this is so that in normal running the bottom valve will be open and the pipe will fill with air to the top valve, then when you want to vent it you can close the bottom valve and open the top valve, then fill it up with water, close the top valve and open the bottom valve, this method is used in industry for dosing large central heating systems/fire sprinkler systems
It may be overkill but I'm an engineer so I tend to over think things, its an option if it does act as a venturi and it can be retrofitted after if needed4600 Gallon Concrete Block and Fiberglass
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26-04-2020, 09:19 AM #7
I did have a situation with an air lock in a 4" pipe a while ago. All I did was drill a 5mm hole to let the air out, then sealed it with a 25mm square piece of 3mm thick rubber, held over the hole by a 4" stainless jubilee clip ( from a rubber connector) around the pipe, over the hole.
I just undid the clip a bit now and again, and could hear the air coming out, didn't even have to slide the clip away. I used it like that for years.
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freddyboy Thanked / Liked this Post
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26-04-2020, 09:11 PM #8
Thanks for all the suggestions......I just have to be brave and drill a hole.
Andy
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freddyboy Thanked / Liked this Post
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26-04-2020, 09:52 PM #9
The problem with any length of pipe that doesn't have flow is that it is a dead leg, potential for bacterial growth.
Keep it simple.
Drill a self tapping stainless steel screw into the pipe.
Undo it to vent the air and refit. Should seal itself but if not a few wraps of thread tape would do, ideally a screw with a flanged head, get them at screwfix etc, usually a box full.
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27-04-2020, 02:49 PM #10
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Fishplanetkoi, freddyboy Thanked / Liked this Post
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