New Backyard system bell sypon won't break

[Lordshandyman]

Lordshandyman, you could just use the bigger pump, just divert some of the flow back into the ft, gives the benefit of adding aeration as well moving the water

Yea, I do actually. I pump directly into the fishtank. Have a SLO into the beds, and a backup overflow back into the sump. What happens is the 2000 gph pump is so strong it actually floods my fishtank, even with both overflow drains working! So I have a valve in line that I tone down the pump. I suppose I could put a tee between the pump and fishtank to relieve the extra, but both ways seem to be wasting energy. My overflow already aerates as well as my two gb's draining. I bought the 2000 GPH pump with thoughts of pumping water on my roof to heat it and would need a strong pump... but I decided that would be a project for another time. Had I foreseen the drains being too high, I would have not been so greedy as to gain every last cubic inch of IBC fishtank by putting the drains as close to the top of the tank as possible. I should have put both drains a little lower from the top... As the water gets over them, they would create a suction and drain fast enough, but my current setup this only happens as water trickles over the top at the same time.

Seems like I remember reading somewhere on this forum your pump should be the same size as your fishtank volume. Ex: 300 Gallon Fishtank, 300 GPH pump. This should give a cycle time of 4 flood/drains per hour. So my 560 GPH pump should be a little overkill too. Actually, the 560 gph pump was giving me more cycles per hour than I wanted with one gb... not for sure how many, but way more than 4. And, when I would try to close the inlet valve to slow the water down, I would not get the syphon to start. Now that I have halved the water to each bed, there still is not enough flow to cause a suction. Oh, I should mention that the 560 GPH pump is actually rated 430 GPH at 5 feet high (my current setup). Oh, and my growbeds are 3'x8'x1' with gravel medium. I figure that each growbed holds 180 gallons with no medium. As to how many gallons with the gravel in it, I have no clue. I use 2" pipe for the overflows into the growbed and sumptank.

Here is my theory.... I used way too big of drain pipe. 1 1/2" pipe requires a massive amount of water to flow before kicking in a syphon. And if I have this massive amount of water flow, then my cycle times are way too fast. And if I try to slow the flow to adjust my cycle times, no syphon. If the size to syphon ratio is proportional, I estimate that I should have used 3/4 drain. I think I will test this theory this weekend. Here is my test procedure, let me know if it is flawed!

I shall put the 560 GPH (430 GPH adjusted) pump back in and shut off the extra bed (no plants growing yet).
In the bed that is operational, I will open the inlet valve to full blast so all the water from the pump goes to the bed and not overflow back into the sumptank. I shall buy a 1 1/2 reducer of various sizes for my stem pipe in my bell syphon:
1 1/4", 1", 3/4", and even 1/2" even though I doubt the 1/2 will work well.
My thoughts are that reducing my stem pipe to various sizes will produce different cycle rates (if even at all) even though my drain pipe to the sump tank remains 1 1/2" and my inlet flow remains constant at 430 GPH. Also, that if I find that a 3/4" stem pipe works the best, I figure that a complete drain system of 3/4" would work the same. So any future beds or systems that I make could be plumbed in 3/4" with confidence.
My goal is to find what size drain creates the best syphons at a certain volume. This in turn will help with determining the most economical pump to piping ratios saving more money up front and in the long run. I shall try to tame the cycling beast once and for all.

I suppose I should ask if anyone has done any studies as to what volume of water flow creates syphon at what size pipe?

[bbikebbs]

... snip ...

Here is my theory.... I used way too big of drain pipe. 1 1/2" pipe requires a massive amount of water to flow before kicking in a syphon. And if I have this massive amount of water flow, then my cycle times are way too fast. And if I try to slow the flow to adjust my cycle times, no syphon. If the size to syphon ratio is proportional, I estimate that I should have used 3/4 drain. I think I will test this theory this weekend. Here is my test procedure, let me know if it is flawed!

I shall put the 560 GPH (430 GPH adjusted) pump back in and shut off the extra bed (no plants growing yet).
In the bed that is operational, I will open the inlet valve to full blast so all the water from the pump goes to the bed and not overflow back into the sumptank. I shall buy a 1 1/2 reducer of various sizes for my stem pipe in my bell syphon:
1 1/4", 1", 3/4", and even 1/2" even though I doubt the 1/2 will work well.
My thoughts are that reducing my stem pipe to various sizes will produce different cycle rates (if even at all) even though my drain pipe to the sump tank remains 1 1/2" and my inlet flow remains constant at 430 GPH. Also, that if I find that a 3/4" stem pipe works the best, I figure that a complete drain system of 3/4" would work the same. So any future beds or systems that I make could be plumbed in 3/4" with confidence.
My goal is to find what size drain creates the best syphons at a certain volume. This in turn will help with determining the most economical pump to piping ratios saving more money up front and in the long run. I shall try to tame the cycling beast once and for all.

I suppose I should ask if anyone has done any studies as to what volume of water flow creates syphon at what size pipe?

I use a 2" down tube with a 1 1/4" reducer under the grow bed. I found that reducing under the bed made all the difference for me. I put an elbow and a short (6") length of pipe after that to help after watching Afnan's siphon videos. This has worked flawlessly since last May. Cycle times are 10 minutes to fill and 1 minute to empty. If you want to slow things down, try a 2" to 1" reducer.