Aquaponics - Update

Where were we. The siphons weren't working and I needed to make gravel guards and add the gravel.

I managed to source a 4" bit of pipe that wasn't a 3m long. I used a bit of duct piping like you would use for putting a pipe through the wall for an extractor fan. You could probably find bits of offcut waving lying around the place though. The gravel I washed and put into the growbeds. I used purple slate. Bigger bits at the bottom and smaller at the top. No noticeable effect on the pond water and the fish haven't died so :) Time will tell if it is an effective grow medium.

I spent a lot of time on the siphons trying different things. What I didn't pick up on and what is very important in that the siphons need a certain amount of water to get going. I was fortunate enough to be able to turn up the amount of water a bit but still not enough to get the siphon going reliably. Enter Affnan. Affnan seems to be some kind of aquaponics genius. Reading his blog and seeing a lot of references to the Affnan siphon I decided to give it a go.

The basic idea is that you use a pipe reducer (although we are expanding) to increase the surface area of water flowing into the standpipe. This causes a Bernoulli effect (so Affnan says) which effectively means that the siphon can be started with less water flowing. The part I am using here is a 3/4" to 1 1/4" reducer. Why this is all still in imperial beats me.




One of the big impacts of the adding the reducer was that my bells no longer fit. Well they fit but there was no room for the water :) I had kind of expected this so I got the parts to make a larger 2" bell.



Bell parts:

• Length of 2" pipe
• 2" pipe cap
• Joiner for putting the cap on the 2" pipe

You would think the cap would go into the pipe apparently not so.

 You can also see that I went straight to the teeth technique we saw in the document about sipons. Much simpler and quicker that drilling holes. I also did not add a breather hole as it was not mentioned on the Affnan spec's. You may also notice that there is no snorkel in this design either. All in all this takes about 5 minutes to make.

After all that the siphons did not work well. One worked pretty well starting a stopping by itself. This was extremely lucky because I was getting fed up at this stage and was loosing faith in the whole thing.

I took the bell off the siphon and had a look at the water going into the stand pipe. What I noticed was that the water was tending to one side and this effectively meant that the water was pouring down one side of the pipe which was never going to block the pipe enough to create the changes in air pressure required to start the siphon. I levelled up the grow bed, previous ministrations where I was trying to cause a u-bend type airlock by raising the end of the outlet pipe had meant that the grow bed was a little off kilter. I straightened it out and checked the standpipe again. The water was flowing evenly down the sides of the pipe so you get a nice circle in the middle. I replaced the bell and guess what.

It worked.

And has continued to work now for the last 3-4 days.

Here it is finished.

I added some companion plants and some herbs at the ends were the grow beds didn't reach and I have planted some shop started lettuce (mostly because I am very impatient) and scattered some seeds. Fín.