Loop Siphon

[Adam Shivers]

How do I regulate my loop siphon?  Anyone know tips, tricks, formulas, ratios, anything?

[TCLynx]

I don't know the math of it all.  I just know that if the siphon is starting but not stopping well (effectively leaving the bed drained with water flowing through the bottom too fast to let the siphon suck air and stop) then the inflow of water to the grow bed is too fast or your siphon is too small or there is some other reason the siphon is having trouble getting a gulp of air like one end is under water still?  Some times a breather tube can help with this situation though they are harder to implement in loop siphons.

 

If the siphon is not starting well, effectively leaving the bed flooded with water just trickling over the top of the siphon, then the inflow to the bed is too slow or the siphon too big.  Sometimes this problem can be helped by adding a couple elbows at the bottom to cause a little air lock to make the water get a bit higher above the siphon before it can trickle over and start fully but then this can also cause the siphon to have trouble stopping.  Some times a slight restriction at the top of the loop or just past the top of the loop can help here too.

 

Siphons can also be tricky in containers that have a varying cross section as the depth changes, like barrel cut the long way.  Since the cross section when the bed is nearly flooded is bigger than the cross section when the bed is nearly drained it can be very difficult to get the flow rates balanced so the siphon will work properly.

 

If you were to switch to the Affnan bell siphon you might have a wider range of operating flow rates.  Google Affnan siphon for info on that.

[Adam Shivers]

Ok thanks I have seen the Affnan Siphon. To be clear, -Is it external?   I have the problem with it not starting sometimes and not stopping other times when no apparent changes have been made. I have also seen it cycling on it's own on both accounts. I mean NO indication what I am doing wrong or even consistant results. ( this is why I thought numbers might help) essencially the Affnan Siphon looks like an external bell siphon to me but I still do not understand what he is talking about either. Sorry for my lack of info to anyone who might be trying to help me!

 
TCLynx said:

I don't know the math of it all.  I just know that if the siphon is starting but not stopping well (effectively leaving the bed drained with water flowing through the bottom too fast to let the siphon suck air and stop) then the inflow of water to the grow bed is too fast or your siphon is too small or there is some other reason the siphon is having trouble getting a gulp of air like one end is under water still?  Some times a breather tube can help with this situation though they are harder to implement in loop siphons.

 

If the siphon is not starting well, effectively leaving the bed flooded with water just trickling over the top of the siphon, then the inflow to the bed is too slow or the siphon too big.  Sometimes this problem can be helped by adding a couple elbows at the bottom to cause a little air lock to make the water get a bit higher above the siphon before it can trickle over and start fully but then this can also cause the siphon to have trouble stopping.  Some times a slight restriction at the top of the loop or just past the top of the loop can help here too.

 

Siphons can also be tricky in containers that have a varying cross section as the depth changes, like barrel cut the long way.  Since the cross section when the bed is nearly flooded is bigger than the cross section when the bed is nearly drained it can be very difficult to get the flow rates balanced so the siphon will work properly.

 

If you were to switch to the Affnan bell siphon you might have a wider range of operating flow rates.  Google Affnan siphon for info on that.

[Kobus Jooste]

The siphons are internal, protected by a larger perforated pipe between the siphon and the media.  Starting and stopping problems can have a number of problems, and as I am not familiar with what you built, I will try to be as general as possible without being vague.  Afnan's bell took away a lot of the issues around stand pipe versus bell diameter.  If those were not properly matched, the water will simply overflow over the standpipe without ever triggering the bell.  If the water flow is slow, it may also simply trickle out if there is enough of a gap between were the standpipe end and the bell top ends - that is the area of air that needs to be evacuated for the siphon to kick in.  Slow flow often does not allow this.  What I also found on my home system is the outflow pipe play a critical role in how the siphon operates.  I have 4 beds with identical stand pipe and bell configurations, but some can operate at lower inflow that others because of how the outflow pipe is configured.  Try the following:  as soon as your bed overflows, block that pipe at the outflow to allow water to back up in the pipe until there is a bit of water in there.  If you let go and the siphon now kicks in, you have the potential that the flow out of the bottom of the siphon is not building up slowly, allowing the siphon to kick in.  I put all my outflows through two 90 degree elbow bends (I know of people who use plumbing s-bends) and this seem to allow flow at a retarded rate until the siphon can kick in.  If the thing does not want to break off, there are the solution to the neck of the riser suggested by Afnan, you can add a breather pipe at the head of the bell (this sucks up air when water levels drop to a certain level in the bed, breaking the siphon) or you can look at reducing your flow rate if all else fails.  Again, some of my siphons break on the first attempt all the time (I have breater pipes) and some stutter through one or two false breaks every now and then.

 

The attached paper may help - my siphons are almost identical to these

 

Adam Shivers said:

Ok thanks I have seen the Affnan Siphon. To be clear, -Is it external?   I have the problem with it not starting sometimes and not stopping other times when no apparent changes have been made. I have also seen it cycling on it's own on both accounts. I mean NO indication what I am doing wrong or even consistant results. ( this is why I thought numbers might help) essencially the Affnan Siphon looks like an external bell siphon to me but I still do not understand what he is talking about either. Sorry for my lack of info to anyone who might be trying to help me!

 

[TCLynx]

if the function of your siphons tends to fluctuate.  Check to see if it is related to the pump flow rates.  If the pumping rate is being affected by something on the pump side getting clogged or slowed down intermittently then that could affect the inflow to the bed and therefor affect the functioning of the siphons.

[RupertofOZ]

So, are you actually running loop siphons Adam... or "bell" siphons??

[Adam Shivers]

It seems to be perfectly stable in that regard, good thinking though! I have changed that a couple of times but side from that I have experienced the same problems in both positions. I really wish I could get to the bottom of this!

TCLynx said:

if the function of your siphons tends to fluctuate.  Check to see if it is related to the pump flow rates.  If the pumping rate is being affected by something on the pump side getting clogged or slowed down intermittently then that could affect the inflow to the bed and therefor affect the functioning of the siphons.

[Adam Shivers]

I have a loop siphon but I did question if the affnan siphon was an external bell siphon of some form previously unknown to me. I was mostly interested in running a loop so that I don't have to mess with media around a bell siphon or another standpipe situation. If I learned of a formula I would like to be able to set it up for others with a simple loop that I once have had so much trouble with!
RupertofOZ said:

So, are you actually running loop siphons Adam... or "bell" siphons??

[RupertofOZ]

If you have a loop siphon Adam... then you don't need any formula.... just plumb it, loop it... and watch it go....

 

Don't understand how/why it "doesn't work sometimes"... what do you mean.... pics might help

[TCLynx]

it was mentioned about not wanting to mess with the gravel around the drain.  Could the gravel be clogging the water getting to the siphon?  Even when I did loop siphons, I usually put a gravel guard around the drain.

[RupertofOZ]

Absolutely... a necessity... and if you haven't, then indeed it's probable that there is some media blocking the outlet or in the loop....

TCLynx said:

it was mentioned about not wanting to mess with the gravel around the drain.  Could the gravel be clogging the water getting to the siphon?  Even when I did loop siphons, I usually put a gravel guard around the drain.

[Adam Shivers]

yes I actually have a guard so that media doesn't clog it and it has flow. sometimes it has seemed to have too much flow... I may be suspecting that a bigger pump may help at this point. yes I will try to get pics, OZ

TCLynx said:

it was mentioned about not wanting to mess with the gravel around the drain.  Could the gravel be clogging the water getting to the siphon?  Even when I did loop siphons, I usually put a gravel guard around the drain.

[Adam Shivers]

The first picture shows through the growbed to the guard. The second shows my loop straight on. The third pic is of water flowing (being pumped) into grow bed.