Backyard Aquaponics
A place to discuss aquaponics

This is great explanation for siphons, should probably go in the siphon thread for those who are looking for it. Can a mod move them? It would make it easier to find.

Good point gemmell - I have just added a link to my previous post which has more information on the siphons

Ell, you never cease to amaze me!

I don't have a u-bend as it were, at least in terms as you have drawn, perhaps that is my problem?

I did finally make some progress from the suggestions you provided on Saturday.

After doing numerous tests with different sized pipes and arrangements below is what worked............................well, almost.

I widened my crenells and lengthened them just a bit. I sized down the cover pipe to 2" inches.

And perhaps the last thing I did may have been most important. I noticed that my drain pipes going from the underneath the grow bed (very little actual drop, less than 5 inches before the pipe 90's and starts horizontal), back to my (2) 55 gallon fishtanks were sloped upward. I hypothesized that the upward rise was creating too much pressure for the siphon to overcome. So...........I raised the stand my 2 growbeds are built on until the earlier rise was overcome and now actually have a small drop from the growbed drain to the fish tanks.

Once this was done the growbeds would fill as usual, but just before the water level reached the very top outside of the cover pipe drain cap, water would begin slowly flowing into the fish tanks. Once this began, my water pump would struggle to pump enough water into the growbed to overcome what was already flowing out of the siphon. If I put my hand over the drain pipe where it dumps into the tank and allowed the growbed water level to raise another 1/8th to 1/4 inch and release my hand from the drain, swooooooooooooooooooooosh, the siphon would kick in and work a treat. A few times the siphon would kick in on it's own intermittently when expected, but not without fail as should be.

So, after reading your last 2 contributions, do I need to do any of the following to have a siphon system that works:

1. Do I need significant vertical drop in the drain pipe?

2. Do I need to incorporate a u-bend into the drain system before it is routed into the fish tanks to assist the start of the siphon?

Or what do you suggest?

Thanks Ell,

TXPower

1" pipe is on the threshold of needing an air trap (it would work easier if it had one) but we might be able to get away without it.

There should be sufficient drop just from the height of the GB alone so as long as the horizontal distance is not too large and there is a gradual slope so that the water can flow freely, there shouldn't be a problem

1) I suggest you shouldn't have increased the depth of the crenellations - wrap some tape around the pipe so that the depth is back to ~1/2" and see if it will kick in

2) if (1) fails then we will need to put in a restrictive device to stop free air flowing into the drain pipe (air trap )

This can be done by raising the outlet pipe as in the diagram above the horizontal and creating a trap in the pipe (hopefully the horizontal distance is not too great - 4 to 5 feet should be okay)

Try the simple ways first before going to the expense of getting PVC elbows etc

Ell, the horizontal run from the growbed drain pipe to where it dumps into the two fishtanks is approximately 3 1/2 feet on one and 5 foot on the other. The slope is very gradual, probably less than 4 inches from growbed to where they dump into the fishtanks.

First, I am going to install a 90 degree elbow (already have some on-hand)clocked such that the opening faces up to see if that creates a sufficient airtrap.

If not.................

I will go back to 1/2" on crenellation height.

If that does not do the trick..........

I will adjust the drainpipes such that there is a gradual rise going to the outlet at the fishtanks and utilize a 90 degree elbow clocked downward.

I will write back soon with a report.

Thanks Ell,

TXPower

Finally!................................. I got it worked out Ell, I went back to 1/2" depth on crenellations of standpipe and fine tuned the leveling of the stand my growbeds are framed into. What I found was that the pump flows well, but would not pump enough volume to both beds simultaneously to overcome the drain rate once the siphon would begin to kick in causing a sort of continual, slow drain. Especially as the water level in the blue barrel the pump is in drew down. I did all testing with empty growbeds, thus the water demand was greater than will be with pea gravel installed and I believe this will be overcome once I put it in. If not, I'll get a pump with greater than 500gph as my current pump is.

Anyway, wanted to say thanks for all the help, I'm finally up and running, will be adding gravel this friday and hopefully after 3 weeks or so cycling I can add fish.

Thanks a million,

TXPower

Glad you got it working

Ell and other bell siphon Gurus, one of my bell siphons is not working right and after fiddling with the inflow rate for sometime I have been unable to overcome a slow continuos siphon.

This only happens on one of the GB's, the one furthest from the FT's. The bell siphons and drain configurations are exactly alike on my 2 GB's, even the drain pipes back to the FT's are the exact same lenght. The bell siphon of this growbed fills and kicks in fine and drains fine. I hear the 1/4" airtube in the coverpipe take a healthy suck of air, sometimes more than once at the end of the drain, but the sphon will not break. It slows, but remains steady and constant.

I am wondering if I were to increase the size of the airtube, or add another airtube of the same size 180 degrees across from the current one, if this would increase the air sucked and thus break the siphon?

or

The outer pipe, the one that keeps the gravel out and away from the bell siphon, has MANY holes drilled in it and they are drilled all the way down to within 1/4" of the bottom. What if I made another outer pipe and drilled less holes or holes only to within 1/2" to 1" of the bottom?

For reference, my bell siphon consists of 1" standpipe with 2" coverpipe with cap, housed inside a 4" outerpipe.

Thanks,

TX

Try just raising the air tube slightly, if you have it ~1" from the bottom then make it 1-1/2''...then try adding another tube after if that doesn't do it

Yeah Ell, I should have stated, I already fiddled with the length of the air tube with no success. So, I will try the dual air hose setup and see if that helps. I'll ring back with results.

Thanks,

TX

OK, I tried changing the length of the airtube first, no luck, then, I added a second tube, then a third, then a fourth all equally spaced around the circumference of the cover pipe. No luck.

I then tried different lengths for each airtube with still no luck. Whilst trying these things I also adjusted the inflow into the GB at the ballvalve with still no luck............. same thing, the siphon kicks in, drains down, sucks air, but not enough to break the siphon and then maintains a slow and constant siphon.

What to try next, reconoiter the outer pipe with less holes thus slowing water inlet, and/or dont drill the holes as far down toward the bottom of the GB?

Thanks,

TX

It sounds somewhat like a problem I was having. I had an obstruction in the path to my siphon, so the water wasn't getting into the siphon fast enough to outstrip the inflow.

When playing around with siphons this week I was coming up with the same problem of it not completely breaking.Solution for me was drilling a 1-2 mm hole into air tube itself about 40-50 mm above bottom of air hose.Equalizes the pressure every time now and works with vastly different flow rates.

K lungy, will try drilling a hole in the airtube itself sounds like a probable fix. By the way, what are they and how did you afix those feet to the bottom of your cover pipe?

Thx,

TX

Just the pipe itself bent out & sanded flat TX.
Makes it nice & stable for me.