Backyard Aquaponics
A place to discuss aquaponics

So this is what I have come up with so far. All the pipe is 2" except the siphon pipe which is 3".

I cant get my siphon to start unless I lift the siphon pipe up a little. Then I can let go of the siphon pipe and it will siphon the grow bed preety fast.

If you need to lift the pipe a little then you need a longer pipe. I had to re-cut some of mine because the space in the top was bot big enough. And when you fill the gb with media it will slow the water when the siphon kicks in.

Try what Duff says, my opinion is it could be a smaller diameter, if the 2" pump pipes are not going full blast with your pump volume.

If you are lifting the 'bell part of the siphon, then by suction you are raising the level of water inside the siphon, higher than in the bed.
I would look at a few things:
1) the height of your standpipe within the bell - is it short enough. Will your GB happily overflow if the bell is removed (if not make shorter until it will)
2) the total height of your water above standpipe is too low to overcome the siphon resistance.

either:
a) your stand pipe is too short
b) you're not filling your bed high enough for your siphon (same as a)
c) the drain of your siphon has a water/air lock or has too many bends.

Ideally, the drain should be free flowing, ie no water is able to sit in the drain pipe and remain there.
If water can sit in the drain, then you need to open the siphon earlier.... hmmm that last statement is going to be hard to explain... I may post a pic...

Your little air break tubing is sticking up out of the water. Is this by design? Usually the air tube has to go out the top of the cap, then bend down and be attached to the side of the outer pipe under the water line. The tubing should end right about at the low water line for the siphon cycle. Apologies if it is supposed to be that way, but I think it is keeping vacuum from forming in the siphon?

As you can (hopefully) see from the pic below:


The first problem is when you have an airlock, and don't have sufficient pressure to push it out.

You can fix it with the second pic.

Note though, that in the second pic, the water si still a bit lower than the GB water. This is because it's slowly freedraining over the standpipe. This means that there is not enough pressure to push all the air out of the bell and start siphoning.
If this is the case, lower the standpipe.

in my experience, the size of your bell does not need to be modified to suit the standpipe.

As dave says, if the air tube bottom is not below the water, your siphon will not start properly, if at all.

So KP you're saying that to compensate for not enough flow to start it that you can reduce the gap rather than reduce the pipe diameter, yes?

I agree about the air line, the end of it probably needs to be down under the water for the siphon to start properly, you only want it to suck air when the bed is nearing empty to help break the siphon.

If you are needing to lift the outer pipe in order to get the siphon to kick in, it means there is probably a restriction somewhere keeping enough flow from getting going down the stand pipe and starting the siphon. Most likely culprit is either between the top of the stand pipe and the cap of the bell pipe or the bottom of the bell pipe crenelations are not big enough. By lifting the bell pipe you are allowing more flow into the stand pipe allowing the siphon to start. so either shorten the stand pipe a bit or you need a longer bell pipe.

Then come to us with the next problem if that doesn't fix it.

My airline was inside the standpipe right above the crenulations. I could get it to drain the growbed and stop the siphon and start to fill again. You all gave so much good information so fast Im going to be figuring out a plan of attack now. Thanks for the quick and fantastic help.

Don't 100% understand your question. So I'll state some facts I've learnt.

1) Gap between standpipe top and bell top has a minimum, but no maximum.
2) Small Air locks can help a siphon that doesn't have enough flow to trigger (see ell's elbow)
3) Large airlocks cause the siphon to never start.
4) No airline is what I use, so can't venture any assistance. The airline should be outside of the bell, and slightly higher than the crenelations. The airline is to help a siphon stop. Add it as an afterthought if your siphon wont stop.
5) standpipes should be between 100% and 200% the inlet pipe size.
6) the bigger the fall the better the siphon, the longer the horizontal travel the worse, if using a hill to gain head, you may run into trouble. Short unrestricted drains are good, such as the second pic I drew where the siphon drain can free fall into the main drain.

ummm that's about all I can think of.
I would not make the gap between the bell and the standpipe less, in order to increase friction to cope with lower flow.
Instead I would put a small airlock on the bottom of the outflow pipe. This is how Ell (the bell god) did it, although I've never tested it, I trust his expertise.

The lock shown below will slow your siphon from starting. This creates a bigger differential between GB flood height and standpipe height.
Therefore when there is enough pressure to move the water in the lock, there will be a lot more pressure to force the air out.


This is useful only if water is slowing draining and the siphon wont start, or only partially starts, leaving a big air bubble in the top of the bell.
This techniques should require a shorter standpipe in order to not overflow the GB.

So the first thing to so is check your drain is short, then shorten your standpipe. After that there's plenty to play with.

Saying that though, it may work. I just wouldn't do it, because it's so much more fiddly altering the bell.

My next design, but I'm waiting on parts will use a uniseal for the standpipe, this way I can reach in and adjust the height any time I please, from low for well rooted plants, medium to help seedlings take, high for seed germination and very high to drown the ants that are annoying me, and any other bug hidden in the top layer of gravel.

hi
have a look at the internet and type 'TANTALUS SIPHON' this SIPHON type might be better suited for your system.

loop or tantalus siphons both work well in this situation.
I don't like tantalus siphons for my own reasons, they're temperamental things, as we generally use flexible hose.
I also know that you can have all the same sorts of trouble with a tantalus as with a bell. Plus bells are prettier, and look more like magic :-)