One more question - are the grow buckets raised at all in relation to the rez? The top of the siphon needs to be at least an inch or more below the max water level in the buckets. As you said - more height is better, but the water level needs to keep going up at a decent rate even after the siphon begins to drain or it may not trip - especially if the flow rate back into the rez isnt fast enough to suck out the trapped air because the vertical drop is too short or not enough horizontal distance.
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Sorry for the multiple repliesā¦ I have been looking back through my notes when I was doing siphon ebb/flow and NFT etc., an dhaving this exact problem.
The final solution was to raise the grow bucket in relation to the rez. In my case, I lowered the rez, but your only option is to raise the grow buckets.
You might try raising them just a little - some pieces of 4x4 under them maybe?
Then, put the siphon OUTSIDE the rez and some distance from it so you can have a horizontal leg in the drain side.
Unfortunately, I think youāre going to need to have the grow buckets quite a bit higher than the rez or you wont have enough vertical drop in the outflow side of the siphon.
If thats not clear, I can do a sketch.
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The first pic shows multiple parts.
The white container is the res itself with a bulkhead going to the pump, a bypass valve, and the return siphon.
The bottom PVC w/ the union in the back is the feed for the pump itself and the top PVC w/ the valve is the bypass coming from the pump ā that can be used to tune the flow into the buckets beyond the 1-10 setting on the pump. That feed goes into the room via PVC and splits into the top-feed bucket system.
The black tubing is the return from the room, it goes into the 90 and up to the siphon which empties back into the res. (The other half of the diamond is not visible in the pic, since itās contained inside of the res itself.)
Yes on all accounts.
I understand that my outgoing flow rate is too low to kick off the siphon, however itās not because of the water level in the buckets being too slow. I can fill all 8 of the 10 gallon containers in 2 minutes if I wanted, but no matter the amount I feed into the buckets the outgoing supply caps at a rate that is lower than reqād to start the siphon. This is where I feel I am bottlenecked via the single return line.
I have over 4" of water above the siphon level. More than enough based on my previous iterations of this system.
Not possible at this time w/o rebuilding the feed system entirely. Thankfully the buckets use standard 1 1/2" PVC for legs so I will be doing this in a future iteration, but for now they are at the height they will be for this cycle.
Thanks for the thoughts, but unfortunately I believe my issue is different from what you experienced. This siphon setup is based on the previous ebb and flow system I had used for nearly 10 years w/o fail. I believe I had accounted for all of the variables but the one thing I didnāt take into consideration was the black flexible tubing. I had never used it before in a setup but I liked the ease and it was what came w/ the bucket system so it didnāt require multiple trips to the hardware store. I never expected it to restrict the outgoing flow, but watching the siphon struggle to start while the water is 3" higher and rising fast has me leaning towards the return manifold.
Once I can finally get the siphon to reliably start I can start to back off the flow to dial it in. I personally like the higher flow rate myself, since the siphon action draws O2 into the root zone and it allows my bypass to strongly flume the water which helps the glycol chiller work better and keeps things stirred up. (No settling of stuff from the return, letting it get sucked into the pump and pulled through the filters for cleaning.)
I got a few chores around the house to knock out but then Iām back at it. Tent harvest is Wednesday so itās time to get the big garden back into rotationā¦ 
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Im probably misunderstanding something still because it sure sounds like exactly the same problem to me
How much higher are the grow buckets than the rez? In other words - what is the distance from the max water level in the grow buckets to the max water level in the rez?
One thing I had a hard time getting in my head was that the flow rate of the siphon has almost nothing to do with the pump flow rate. Its determined by the three things.
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is of course is the size of the pipes, bends, ells, etc. as far as restricting the flow. I dont think this is your problem though.
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The over all āfall distanceā or head height from the top of the siphon to the top of the water in the rez. This is critical. If you have no fall distance, you have no flow. More fall distance, faster flow, better tripping.
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Number two goes along with the distance between the top of the water in the grow buckets and the top of the siphon. Again, less head height = less flow. Number two however, is the more important one.
A siphon will work great if the grow bucket is low IF you can get it to trip AND you have enough fall distance to create enough vacuum in the drain side to SUCK the water through the system. Siphons suck water - they dont push water. You cant suck unless you have fall distance.
In other words, its the total āhead pressureā created by the difference in height between the water in the grow bucket and the water in the rez combined with the total vacuum created on the drain side. You need some of both idealy, but its the vacuum side that really does the work. No vacuum = no suction = no or low flow.
The flow rate of the pump has zero effect on the flow rate of the siphon. Increasing the flow rate on the pump only speeds up the start of the siphon. How fast it goes after it starts is entirely controlled by the fall distance on the drain side. Its the vacuum that does all the work and determines the final flow rate - far more than pipe size and independent of pump flow rate.
If the bucket and rez, and especially the siphon and the rez, dont have enough head height difference, you will never get any āsiphon actionā no matter how powerful the pump.
What makes the siphon work is the fall distance. As the water falls, it creates a vacuum in the siphon that sucks the water out. The pump in this case is doing NO pushing. It only controls how fast the head builds up, which determines how quickly and reliably the siphon trips. The over all flow rate is based only on the amount of vacuum you can create on the drain side - which means you must have some drop distance. More drop distance on the drain side = faster flow.
Also, as your rez fills, the difference between the siphon top and the water in the rez gets less and less. That means a slower and slower flow rate as the rez fills.
In your case, the top of the siphon is below the top of the rez. That means the bottom of the siphon drain side is under water. The only part that counts is the part that is ABOVE the water. The water must fall for any vacuum to be generated.
For example, you might have a drain leg on the siphon that is 12" long, but if the water level in the rez is up near the top of the siphon, you will never get any suction from the falling water - because the water has no distance to fall. The siphon wont fully trip because it cant suck the air out due to too slow a water flow.
Remember that old science experiment trick for collapsing a metal one gallon can from air pressure? You take a gallon container full of water, seal it up, but attach a drain hose to it, then climb up on the roof and let the hose hand down to the ground and let the water drain out. The vacuum from the draining water will collapse the gallon container.
Its exactly that effect that makes the siphon work - not the pump.
Even if it does trip, the flow rate will be reduced based on the height of the water in the rez in relation to the top of the siphon. You absolutely must have some distance between the top of the siphon and the top of the water in the rez. More is better. In your case, the siphon will stop working completely once the water in the rez gets up to the same height as the top of the siphon- and - it will go slower and lower as the rez fills. At some point, it wont be able to keep up with the pump and you will get over flow.
OR
I am still missing something about your setup
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Sorry to be a pest - Iāll stop after this one I promise 
This is what Im talking about. If I am understanding your setup correctly, you have some head height between the top of the water and the top of the siphon - BUT - look at the difference on the drain side between the top of the siphon and the water in the rez.
If you do not have enough fall distance on the drain side - inside the rez - the siphon will never create enough suction to suck out the trapped air and the flow rate will be greatly reduced. The drain side is far more important than the fill side.
I think you need to get the siphon raised up a good bit higher than it is.
It might also help to put the siphon by the grow buckets instead of directly in the rez. That way you would have some horizontal pipe in the drain side. That can work almost as well as vertical distance when the siphon is first starting.
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Aha, I believe the image shows what youāre missing on my side. The grow beds are actually on legs, standing 10" higher then the res and the end of the siphon is never actually under water.
Since I last posted I took apart the drain-side and built the tubing to PVC manifold. While I was doing this I think I discovered my bottleneck. The valve that I had in place on the tubing reduced in diameter by about half in the middleā¦aha! Since I already had the manifold built I put it in place, connected the siphon, and she fired right up the first run.
Right now I am playing around to learn the minimum and maximum flow rates so I can dial in what is required to start the siphon every time while still filling the beds as quickly as I wanted.
Hereās a quick timelapse from the res side of a 30 minute cycle.
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Yeah, I missed the legs and the extra height on the grow bed side side.
Im still surprised it works as well as it does with that short a leg on the drain side of the siphon inside the rez - or that rez is a lot taller than it looks like?
In my tests, the length of the down tube on the drain side of the siphon (the part inside the rez on yours) had a much much larger influence on flow rate and tripping than the head height above the top of the siphon.
Glad its working!!!
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The res is a 35 gallon horizontal leg tank, about 2ā tall.
Iāve always found as long as I can feed enough water in I can trip the siphon, then itās just a matter of dialing it back to ensure the siphon breaks. You need enough turbulence in the exiting flow to create a water lock, but I can achieve that with an elbow as much as a long length of PVC.
One interesting thing I did have an issue with this time was cavitation from the siphon. As the falling water hit the surface it generated bubbles and with the pump inlet right below they were getting sucked right in. They werenāt very big but they caused quite a bit of noise in the pump and you could hear the air moving through the pipes. I redirected the siphon output and the problem went away, but thatās definitely the first time Iāve had to deal with something like that. The downside of a really strong pump ā I can actually pull bubbles in faster then they can rise to the surface.
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I realized I never posted up a photo of my little flex pipe to PVC manifold.
You can see on the left the two black flexible tubes coming through the wall, those are the return lines with each serving 4 buckets. I had originally planned on that laying flat but the tubes tell you where they want to sit, not the other way around. 
Itās well below the high water mark so it hasnāt caused a problem.
After quite a bit of time flushing the system I dumped the res and refilled entirely with RO water. I went ahead and repurposed my booster pump from the HPA to increase the pressure into the RO system, since the house water pressure just barely hit the green area. Going from 30psi to 100psi really increased the flow rate of the RO so I didnāt have to wait forever for the 30 gallons to refill.
Water started off at 0.0 EC but after a night of flushing Iāve crept back up to 0.3 ā so another dump and fill is in order for tonight.
Thankfully I have the MPT fitting arriving today that will connect the bottom of my spin-down filter directly to the drain in the room. With this I can turn off the valves going into the growbeds and open the spin-down valve, so now the primary pump will empty the res directly to my drain. If my math is correct Iāll dump the entire res in about one minute flat. Thatāll along with the booster pump on the RO system means I can dump and refill in an hour or so. Much more manageable.
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Sorry man, Ive been wanting to pester you with questions, but Ive been under the weather.
One quick one - what kind of fill/drain cycle times are you ending up with? Do you have any way or any plan to vary the timing if needed/wanted?
Looking insanely neat as always
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No worries man, take care of yourself first! Hope youāre on the mend!
Right now itās about an 8 minute fill and a 3 minute drain cycle.
I actually have multiple variables I can adjust to change timings. Changing the bypass valve or turning up/down the pump drastically changes the fill time, but Iām pretty much locked with the drain time. I could add a reducer on the end of the siphon to slow the drain, I assume, but I donāt think thatāll be needed. I canāt think of any way to increase the drain times, thoughā¦
The past few days Iāve been experimenting with using the Autopilot recirculating timer to run the pump. I currently have it set to 10 mins on and 5 mins off. The siphon still fires at about the 8min mark, so that gives me 2 minutes where Iām pumping fresh res water into the beds to make sure I flush anything out. I also extended the dry time (off) a bit longer than needed, but I like having the ability to control the fill and drain times, so I might continue to run this way.
I installed the drain to waste lines this weekend for both the RO filter and the spin-down drain. With that I went ahead and did another flush of the res and brought the EC down from 0.4 to 0.1. There still some residual stuff flushing out of the media since my RO comes out at 0.0 initially, but Iām at a good enough starting point now.
My Jacks 321 arrives on Tuesday so I will be mixing up nutes and popping beans this week. Now to figure out what I want to run first from this crazy stash of seeds.
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That all sounds good to me. The only way I know of to shorten the drain time is a larger siphon, and/or fewer restrictions in the piping etc. I dont think I would worry about the time it takes to drain though. Its the total ādry timeā thats most important in my mind, and Im not sure you need any longer than you have now for peak oxygenation in the beds. I like the pump running after the beds fill to flush things.
Can you use that timer to increase the dry times above what you have now? Sounds like that would work - if - you feel the need.
You may be one of the people I owe an apology too as far as me switching to Jacks. I cant remember for sure, but I think you tried to talk me into switching way back in the early HPA days. Of course, I ignored that good advice until recently. Now that Im using Jacks, my PH and contamination troubles seem to be over. Im having zero PH drift, zero smelly rez and zero cloudy water. Im amazed at the difference switching to raw nutes has made. The Jacks is working better than even AN nutes with PH Perfect and me adding extra MES buffer.
Im curious how long you have been using Jacks and if you change anything up for hydro use? Ive only been running it a few days, and its just the straight Jacks Hydro 321 formula with no adds or mods.
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Yup, I can increase the OFF time to increase the dry period. I know most F&D setups are only a few times a day but Iāve always had incredible growth using my 24/7 E&F. I think by increasing the dry period slightly there might be even more I can pull from this, though.
I always had problems with Megacrop, which is why I searched out a new nute line. I was running HPIās Ionic line for a long time (MI made and worked well), and it was clean so never clogged my nozzles.
Yup, exactly why I changed over to Jacks myself. I tested small samples before so I knew it worked well, but watching others w/ totally clear resās got me to try them.
Just switched to Jacks for this run myself. I am using Greengeneās formula though, which is a slightly modified 321.
Popped new beans last night for the first run in the new setup.
4 of each, Jedi OG from Vader/Oceangrown and Roid Rage v2 from Darkhorse Genetics. I have Farmer Freeman sex tests on hand so any that end up males will be replaced with random FEMs from the stash. Itāll be a bit of a cluster running reg seeds until I can get some new moms established in the 2nd tent.
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I like jacks brand based off theyāre $$ range 
Whats the difference between them ?
www.advancednutrients.com and www.foxfarm.com Im buying and replacing out the used and empty ones āscotts miracle growā a.k.a General hydroponics.
Fox farm bundle packs for $80-$90
Advanced nutrients bundles range anywhere from $145 + or more.
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Just 24 hours after being put into the shot glasses all 8 seeds have started to sprout tails.
They were all transferred to paper towel and placed into my sprouting cabinet. I will be mixing up my Jacks and setting the res later on, since these look like theyāll be transferred into the system in the next few days.
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I went ahead and finished mixing up the Jacks tonight, giving me 32 gallons of fresh nutrient solution running through the system. I followed the base formula (3.6/2.4/1.2) and even after a few hours of cycling the water is still clear to the bottom with no visible sediment.
A bit of pH down was needed to get back into range, but I believe that was me neglecting to pH the media. Once it stabilizes this will be less of an issue.
The seeds have really taken off and look about ready to go into the grow beds. If I wait too much longer Iāll risk the taproot growing into the paper towel. Unfortunately it looks like one of the Jedi OGās is a bit slower to pop than the rest, though I still have hope sheāll pull through.
Hopefully the next update will be seedlings going into the room. 
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Well last night I finished getting everything ready and was all set to put the sprouts into their new homes.
I was quite surprised when I opened the paper towels ā 3 of the Darkhorse Genetics Roid Rage had already shed their shells and were wandering the towel looking for light. Thankfully the 4th Jedi OG had popped completely as well.
I dropped them into each bed a few inches below the surface and then covered with plastic cups to act as humidity domes until they get established a bit further. (Each cup is getting a spray of water on the inside any time I see it dry.)
This morning when I went and checked on things 3 of the 4 Road Rage had already popped above the hydroton and 1 of the Jediās was up.
I am afraid that the late-popping Jedi might have some issues. Since its taproot was smaller than the rest when I put it into place it fell down into the hydroton a bit deeper than I normally like. I actually have no idea how far it went and I wasnāt going to dig in to find out ā I know from experience that will just make it fall further and/or crush the taproot while looking for it. Hopefully she finds her way to the surface, but weāll see.
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Cool looking setup!
Are those some sort of mesh bags the hydroton is in inside the tubs?
Are you planning to cover the top of the hydroton in any way to try to keep light off/reduce any algae growth?
Any plans to fight roots getting into the drains? The mesh bags maybe? I had zero luck using silk screen fabric to stop roots. I forget what mesh I used, but they acted like its not even there and send fine hairs through no problem and just start growing on the other side.
You do know that people like you give people like me a bad name - too f 'ing ng neat, organized and clean!! 
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Nice setup. Iāve seen videos on YT with similar, but using Coco as the medium. Top feed RDWC sounds like a great plan!! I donāt think he did anything special to shield the media from light.
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Yes, those are the screen pots that come with the planters from The Bucket Company.
Thereās a two-fold system for solving that. First is the bags themselves ā there is a slight gap around all edges which allows for air-pruning during dry cycles. The second is part of the bucket design itself, hereās a shot of what the bottom of them look like.
Those bubbles on the bottom of the planters keeps the bag w/ media elevated, allowing for more air-pruning.
Hereās a snap from one of Medgrower1ās videos where he is transplanting from the 3 gallon to the 10 gallon buckets. Look at those roots.
If I do end up with a problem I can just lift the bag up, pull the roots, and drop it back in place. That was always a problem in the past w/ hydroton but The Bucket Company solved this perfectly with the liners.
I never really had a problem with algae on the top. I did use panda film in the past (white side up) to place over everything and around the main stem, mainly to help reflect light and reduce temps so I will probably do this again once the plants are tall enough.
Much appreciated man. Iām really happy with how this all turned out.
One of the best parts is something I donāt really show off, too. When my reservoir chamber is closed up you can be standing 2 foot from it and you will hear a slight hum from the air pump, but nothing else. Outside of the controllers mounted above that part of the workbench youād have no idea what is running in there.
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