Now, those fittings are not easy to get here, so there I spent some time looking in generic hardware stores for the parts but ended up going to a local plumbing supplies place DPL. I have to say at this point that the guys here were excellent and very helpful in cobbling together the parts I needed for the system. It was a little different then in the video above, but it does seem to function as expected, although at this stage if any plants grow remains to be seen.
The parts I used to make the siphon are as follows:
- 3/4"Straight Overflow Tank Connector
- A threaded elbow probably also a tank connector
- A threaded brass piece to join them
- A length of 25mm overflow pipe (length will depend on your grow bed size)
- A longer piece of 38mm pvc pipe
- 38mm pipe cap
- Joiner for pipe and cap
Now ideally you would get bit closer to what he has in the video but I was trying to do it in a weekend and not have to order stuff in, in practice that probably would have been cheaper, easier and quicker, but who knew. I already had a pump for my pond so I was sorted there, definitely not the perfect pump for this but will do the job. With all the parts assembled (and still not quiet believing it would work at all) I tried it just holding the pipe filling the tank and low a behold it did actually work.Now having done some things like this before I am all to aware of my own shortcomings and that I am not nearly as clever as these people on the interweb I was dubious of leaving it running without me watching. This raised issue for about the general operation of the system. You see, as it was not a closed system, i.e. if for some reason the siphons became blocked or the grow beds sprung a leak there was nothing to stop the pump from pumping all the water from my pond, burning itself out and killing my fish. Hmmm.
Thinking about this the first thing that springs to my is some sort of ballcock. Now, being filled with the joys of clever non-mechanical DIY siphons I shied away from buying a traditional ballcock. I figured I could make something similar. I came up with a number of prototypes and spent many evenings trying proofs of concept. All failed. I ended up buying a ballcock in the end. They are designed that way for a reason it would seem. You need the distance between the float and valve to create the kinds of force necessary to compete with the force of the water. Obvious no that you say it but was fun learning anyways.
To my dismay the purchased ballcock didn't work either. The rate of flow for a bog standard ballcock was simply not enough to cope with all the water my pump was moving so even fully open there was still water flowing up to the grow beds (not that I hooked them up at this stage). After two failed attempts at drilling out the valve on the one I had I resigned to wait until the weekend to get back to the guys at DPL to see if there was anything to be done.
Fortunately, there are various rates of flow decided by the piece I had tried to drill. Unfortunately they did not have the fastest flowing one as these has not been seen for at least 18 months. I settled on the red ones and got a few in case I tried my hand at expanding it once again.
I then proceeded to plumb in the actual grow beds and get the system going properly.
It did not. The water seemed to be constantly flowing out of the pipes. I played around with my siphons and realised that the siphon was never actually stopping. You see when I had been trying it I was only filling it up to the point where it stopped siphoning and then moved the pipe back into the pond, so the siphon was never running while the grow bed was filling. With the water coming in from the pump constantly there was enough to keep up with the siphon at the end once it slowed as it reached the bottom of the grow bed. This mean that the siphon never disengaged and it would constantly trickle out. Now I figured a hole above the main intake holes would sort this out but I needed some confirmation. I did some googling and found this very useful document regarding siphons, thanks to U of Hawaii. Now this document is great for explaining how to make a siphon. One of the things mentioned is a snorkel. Now you may have noticed, as I did, that there was no snorkel in the video, but there is a small how drilled above the other holes which serves the same purpose.I adjusted my siphon but reducing the length of my stand pipe (not sure if this was a good idea). Changed my inlet holes to "teeth" as described in the document above and added a small hole. These changes seemed to have the desired effect.
I have noticed now that it is still not quite right. The siphons are not kicking in enough. I need to play with it some more. So, next jobs are to create a gravel guard and add the gravel.
