Auto- Siphons aren't working 100% of the time

[Jon Easterling]

I have 4 grow beds each with its' own auto-siphon. Occationally one of the beds(but not alwayts the same bed) will not start draining and will overflow. At other times, one or more of the beds will drain and the auto-siphon will continue to drain and not let the bed fill back up. All for auto-siphons drain with a 3/4" drain and they all 4 feed into a 1" main drain line.

DO I need to have a larger main drain line? or do I need to run a seperate drain line from each bed?

any ideas?

[TCLynx]

A larger drain or separate drains might help the problem.

 

I highly recommend an overflow be installed in each bed so that if the siphon fails, you will not overflow out the top of the bed and loose water and possibly run the fish tank dry killing fish.  An overflow is always a good idea.

 

So, with the combined drain, it is possible that you are getting air locks or suction that is causing odd things to happen, you might need to add some vents to keep such things from messing with the operation.  A vent is as simple as adding a T with a piece going up above the top of the grow beds anywhere that suction might be causing a bed not to stop siphoning or one bed's siphon causing another bed to start draining early.  Or Where ever an air lock might be keeping a bed's siphon from kicking in properly and thus causing the overflow issue.

 

Normally, when a bed reaches the state of being flooded but the siphon only trickling over and not kicking in it is a sign that the inflow to the bed is not quite enough, this could be intermittently caused by gunk slowing the flow of water through the ball valve feeding the bed or more of the flow going into a different bed.

When a bed gets drained but the siphon doesn't quite shut off and the bed is at a state of water constantly running through but never flooding it is a sign that the flow into the bed is just a little too fast to allow the siphon to cut out and this could perhaps be caused by the ball valve being left a bit too far open or maybe by a different beds flow being blocked up.

 

I'm thinking more likely your small drain and having several beds sharing it could easily be causing many of your issues.  If you either rout the drains all separately or up size to at least a 2" shared drain line and perhaps a couple vents (by the way, connecting an overflow from higher up in the bed to the same drain line will act as a vent so long as there are no traps) will probably take care of many of your issues.

[Mike Konshak]

Jon, The cross sectional area of 3/4 dia pipe is 0.474 sq inches. Multiply that times 4 drains and you get 1.767 sq in needed for a common drain. A 1" dia pipe has a cross sectional; area of only  .787 sq inches so its obvious you are restricting the free flow of the drain necessary to make an auto siphon work, plus you have more water going in at one time that the drain can handle (you're creating a flood condition) causing the overflows. A 1-1/2 pipe has an area of 1.767 sq inches, but you really need a 2" drain, as TC mentioned, with a cross section of 3.14 sq inches, if you retain the common drain system.

My advice, making it easier to troubleshoot, is to make all 4 drains independent, going from 3/4" (or 1") auto siphon into a 4 individual runs of 1' pipe to your tank. That way you know which grow bed is acting up at the time.

 

Mike

[Leo White Bear]

Jon-

  To help you, I think we need a bit more info, like how big is your pump / pumps, stand pipe diameter and length, where does the end of the stand pipe sit in relation to the inside top of the bell.  If the siphons don't work is the problem more relivent before a rain (during low pressure systems coming in).  Is the stand pipe / bell 2 - 1 ratio.  (1 inch stand pipe / 2inch bell).

  I know that these sound like petty questions but in my experience, all these things affect the performance of the bell siphioning effect.

White Bear

[Jon Easterling]

Thanks for all the reply's!! I think I will go with seperate drains from each grow bed. I'm pretty sure my pump is a little over sized, so I have done a few things to restrict the water going into my grow beds, but it is easy to adjust. My fish tank is 250 gallon, and I have a 55 gallon barrel for the sump tank. My pump is one that I already had so I was just trying to make it work. It is 1200 gallons per hour. I have ball valves at the end of all my suppy lines to control the water everywhere, but before the valve for the fish tank I put a T to drain into the fish tank before the valve. I can turn off all the valves and the water will just circulate betwen my fish tank and the sump tank. I am still working all this out and working on growing bacteria with out the fish, so shutting down and replumbing is not a problem.

 

Thanks

[TCLynx]

And re plumbing the drains, if you get some of the parts ahead of time you will be able to get at least one of the beds back online probably in a matter of minutes after you start.