Backyard Aquaponics
A place to discuss aquaponics

Dave - I think that design would result in one of two thing - depending upon your infow and outflow parameters:

1. Siphon will slow but not stop - making it difficult to get it to stop once it gets to the bottom

2. Siphon will stop while water level is still high

I believe that Steve did do a similar thing once (unknowingly) - though just with one cut - and was able to get it to work. However he was then unable to replicate under different conditions. Give it a go though and let us know how you go.

Will do Veeb

I am interested in how it goes too Dave, I tried putting one slit up the side of the pipe but didn't have much success...but then again I was a tad biassed

For what it is worth, I have tried the slits in the side of the pipe and have consistently had problems with them filling with bio sludge and algae. It helped to put a lid over the assembly to keep out the light but still it eventually clogged. The advantage of the auto siphon (as probably stated before) it has no moving parts and it is hard to break. I use the biggest crenelations at the bottom possible so I have no clogging. Of all the problems I have faced in AP, the function and reliability of the auto siphon has never been one of them. I will admit, it is fun to play with new ideas... Play on Dave.

hey steve, good idea, had something similar in my head, i wanted to bore holes there
but i did try to raise the air hose to the same height and the siphon stopped sucking at full rate at +- 3 cm from where the air tube level was, didn't brake the siphoning action, just slowed it dow

will try it your way to see what happens

For months I put up with a slow "break".
I use a loop type siphon made with threaded pvc pipe and elbows.
It has an airline to stop the siphon.
The airline starts just above the bottom of the siphon tube,
It comes up past the top of the loop, and then doubles back straight down into the top of the loop.
The apex of the airline is always out of the water.(2-3 inches)
Although the flow seemed to slow when the airline was exposed, it still took between 1-3 minutes to stop.
Eventually I figured out that the airline was full of water, (from the fill cycle) which needed to drain before the siphon would break.

I took a fine dress making pin and poked a tiny hole into the apex of the airline. (well above the fill level)

The very next cycle, the siphon break was instant!
The pin hole allowed the airline to drain quickly which in turn snapped off the siphon,
and the pinhole does not introduce enough air into the system to effect the drain speed.

The system has not faltered since (2 months)

Good tip Dicko!

Another essential item for the BYAP tool box

...along with the dress to be worn by those AP'ers who are too scared to use autosiphons

We're not all cross dressers VB ... ... might be just a QLD thing....

Good info Les, but I must be a bit slow on the uptake because I can't get my blasted bell siphon to work. can anyone help me.
My outer pipe rises as the water rises and does not set off unless you lift it up further. i do that to stop the bed from overflowing
I have a standard AP grow bed with 30 cm deep.
I have a stand pipe which is 25 mm diametre (internal measurement) at a height of 18 cm.
Outer pipe is 50 mm diametre and 21.5 cm height.
the air hose is standard 4 mm poly that starts 10 mm above cut outs and stops 30 mm lower than the cap.
Don't know why it is not working.
Here is a few pics.
Would be happy with some guidance before I go crazy
There is a slight incline from bottom of pipe work back to the sump to ensure water is kept int he pipe work

**Disclaimer - sorry if this is ridiculously simple, but it needs detailed explaining imho.

Your outer pipe rises because it as a whole is lighter than the water.
If your outer pipe was filled with water then it would be heavier.
So we can deduct that water is not going into your bell, but instead lifting it above the surface.
This means that the air is trapped in there and this is a problem.
First thing I would look at is your drain, and you have so nicely posted us a pic, so I can almost state the following with 100% surety.

if you have a look at the picture below:


I believe you have a particularly bad version of the top GB.
In that your pipe running from the bottom of your bed is mostly horizontal, but because the pipe's flexible, probably has some uphills and some bumps.
1st I would recommend that your drain pipe has 3-5° of fall. eg. at the GB it should run downhill to the sump at an angle of 3-5° this is recommended for plumbing drains in the house, hence why all DWV fittings are annoyingly 85 or 87° and not 90°.
2nd, I would suggest you copy the bottom GB. this will mean the siphon can dump happily, and provided your drain drains, we shouldn't have a problem. You need to introduce air near the GB though, to allow the air in the bell to escape.
You could plumb a small pipe from under your GB up to above the top level to allow the air out, but this is a tough particular about being setup 'just so'
3rd I think your standpipe is less than 50mm so drop that size out the bottom, and arrange it so it sits loose inside your 50mm drain

Please see this thread for further reading

If this doesn't fix your problem, I would suggest you shorten your standpipe a little bit.

1 good test for a good standpipe, is that if you can blow through it easily, then it should work, if it resists you, you may be in trouble.

Your two key points I latched onto for this diagnosis were:

and

as well as the pic of your drain.

Might I ask why you think it's important to ensure water is kept in the pipework? (sorry for only bringing this up now, but I only just read that line properly)

Well from misery to elation in only a few seconds. Excellent work Kuda.
I changed the configuration of the pipe work below the bed so that it runs slightly downward and instant success.
I was looking at a youtube video and I am sure he said his pipe work ran slightly upwards to the sump. teach me for going else where.
I was under the impression that for the bell siphon to work, the pressure had to build up in the pipes. Therefore keeping water in the pipe would help this to happen.
Well, some times I think to much.
Good work and many thanks from a happy APer

Sometimes, if the flow is not high enough to start the siphon, we add a waterlock to resist the flow and create a higher head, yours was just much too big.

Good tip Kudapucat! To Gilly and others: FYI most bell siphons are setup with a vertical standpipe with both ends open.