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Bell siphon sizing
http://byap.backyardmagazines.com/forum/viewtopic.php?f=8&t=20694		 Page 1 of 1
Author:  Lycoming [ Feb 18th, '14, 23:36 ]
Post subject:  Bell siphon sizing
Hello all,

I'm new to aquaponics and trying to determine if am sizing my bell siphon properly based on the rest of my system. Basically I am wondering if the tubing size of the siphon MUST be larger then that of the H2O supply line in order for the siphon to be effective.

To add a few details:

My prototype system uses a 50L tank. I have read that media takes up ~ 60% of the volume, so therefore I would have 20L of water in my tank. If I am filling this at 1 L/min, using 1/2" PVC pipe, it should take 20 min for my tank to fill and siphon engage. At this point, my siphon is also made of 1/2" PVC (the standpipe), with a 1" siphon shroud (terminology...) and cap. So that further explains my question, since my input and output lines are the same diameter.

Would this be sufficient to operate? Or should I find a 1" standpipe?

Thanks for any advice!
Author:  CJ-California [ Feb 19th, '14, 08:05 ]
Post subject:  Re: Bell siphon sizing
I have never actually ran into this problem. But in theory, you would have to up size your pipe .5 to .75 or 1. So yes, up size your pipe. Typically you would have up sized your drain lines from the beginning so this wouldn't of been a "potential problem".

In an AP that has a sump (Chop/CHIFT PIST); typically you would have a 1/2" feed from pump to a 1"or 3/4" flow out of the FT.

So another possible fix would be to: :thumbright:
Reduce size of the pump feed either with a smaller pipe, or
Reduce the flow of the pump feed with a ball valve, multiple turns, or height.
Author:  PedalingBiped [ Feb 19th, '14, 09:02 ]
Post subject:  Re: Bell siphon sizing
Because the formula for a circle includes radius squared. What happens when you double the circle, you have 4 times the volume.
This is a hard rule. Works for every doubling
So your 1 ltr/min at 1/2 inch would mean 4 ltrs/ min at 1 inch. 1 1/2 inch = 8 lts/ min 2 inch = 16 ltrs/ min.
Author:  Mr Damage [ Feb 19th, '14, 11:22 ]
Post subject:  Re: Bell siphon sizing
A 1/2" standpipe will be fine for a 50Ltr GB... I use a 15mm (19/32") standpipe for 50Ltr GB's... and once the GB in-flow is tuned to get the siphon operating I usually get a 5-6 minute complete flood and drain cycle.

A 1" standpipe is massive overkill for a 50L GB. It would require a much bigger pump and once the flow is tuned it would give extremely rapid F&D cycles of around 2 mins, which doesn't allow solids to settle out in the GB's, leading a lot of suspended solids in the FT water.

I make and sell plenty of siphons and I rate 1" (25mm) standpipes for GB's of 200-600L capacity... and 3/4" (20mm) for GB's of 100-300L capacity... and that's not through the use of mathematical calculations, rather plenty of trial and error.

Calculating your GB in-flow is a waste of time, as the flow will need to be "tuned" to get the siphon working... essentially the required GB in-flow is determined by the diameter of the standpipe.
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