So, I just finished my first bell siphon and have started testing it out and messing with some different variables. Right now, the drain pipe is 1/2 inch pvc with an 1 1/2 reducer acting as a funnel, with a 3 inch pvc as the bell dome over the top. It functions, and these are the results I am having:
With a trickle of water input, my 28 quart grow bed will fill in about 8 minutes, then the siphon will start trickling. It will take between 45-50 secs for the siphon to fully start suctioning, and then it takes around 4 minutes for the bed to drain. This is all without media, I plan to put a 4 in. pvc pipe around the bell dome as a media guard.
My questions are:
Would adding an elbow joint to the drain area increase the speed of the suction without decreasing the speed of the drain time?
Are those times ok for plants? Should they ideally be longer or shorter?
Sometimes my siphon continues to trickle for about 2 minutes after the bed has drained; it almost gets into an equilibrium with the input for about 2 minutes before it sputters out. Is this ok?
Thanks for any advice you have!
Adding an elbow to the outlet will likely decrease the time it takes to initiate the siphon, but it will slow down the discharge flow rate a small amount...however....when you add the media you will be reducing the volume that has to drain by ~60-70% depending on the media. You should target a total time of 15-20 minutes between gurgles...however...this is just a rule of thumb, the plants will let you know if something is not right. Reducing your flow rate or dropping the outlet pipe elevation (if you can) will help break the siphon. A breather tube will also do the trick.
Also, you may want to consider going to 1/2"-->3/4" or 1/2"-->1" reducer on your standpipe, the size jump you are using is a bit much IMO.
I developed what I call the EZ T Siphon - here is my video on it if you want a simple alternative to the bell
Putting a double loop siphon in the grow bed is a good idea, I just see serviceability issues - have to remove the gravel to remove the standpipe. Even using 1" to 3/4" tee and 3/4" street elbows that doesn't fit within a 4" media guard, even barely in a 6-inch.
I have had a buried siphon for 3 years now and never needed to service it, I'm just not convinced yet that a need to service will happen frequently enough for it to be a concern for me. Others may worry about it more - but I like to live on the edge :)
Well I forgot to mention - Murphy is on my team
I had several of the 36 flood and drain beds I had running continually become clogged at the bell (or bulkhead for those that I had plumbed using a mega-siphon 2"stand-pipe, 4" flare and 6" bell housed externally in 1/2 of a 15 gal drum. Roots were the culprit and had to be constantly trimmed back as they would begin to grow into the piping. These beds had predominantly greens (mizuna, sorrel etc) that would grow for extended times and be cut weekly so the roots would really develop.
Ok Scott, I'll shut up and bow to 36 times the experience of failure.