Backyard Aquaponics
A place to discuss aquaponics

Also, how high off the bottom of the tank should it be on the bottom?
Thanks again.

Yep, a bulkhead at the overflow height. This will be the constant height mark in a Chift Pist sytem for example. It would normally be at the bottom with a spacer of some kind so the suction doesnt suck the pipe onto the bottom. Heres mne before it went in:

Much harder to see once its in (here the tank is filling to height):

Awesome! thank you very much for the pictures and explanation.I kinda figured I had it right in my mind but wanted to be sure.

I actually have my uniseal or bulkhead fitting a bit lower than the water height, so I can adjust it up and down a bit with the plumbing, if the bulkhead is right under the lip of the tank you don't have any leeway if the pipe doesn't keep up with the flow rates.

Anyway, I didn't want to glue the pipe inside my fish tank in case I needed to pull it open for cleaning but I had a problem with the big fish knocking the pipe loose so I drilled a hole through the pipes and threaded a zip tie through any of the loose connection so I can still go in and cut the zip tie and pull the pipe apart if I need to but then put a fresh zip tie back to keep the fish from knocking things apart and swimming into the pipes again.

That's a great idea with the zip ties. I was racking my brain on how I would be able to make an adjustment if needed. The only other thing I was thinking though is with what I have I would pretty much have no choice but to set it at one level since I will have to drill through the sides of both of the fiberglass tubs I have in order to connect them together.I guess that will kinda rule out an adjustment on my system.

Well not necessarily but I would probably need to see pictures to understand exactly what you are saying.

But anyway in this picture

There are two tanks with pipe plumbed through them and aprox the same height but the section of pipe between them could be adjusted higher with some fittings if you wanted the water level higher in the fish tank, would just need a T at the highest point with pipe going up as a breather to keep it from turning into a siphon or getting a vapor lock.

Actually if you look at that diagram you just posted~my tanks I have are pretty much the same.They're 2 lobster tanks that are made of fiberglass and approx.250-300 gallons each.I have 2 bath tubs for GB's and a blue plastic drum I'm using for the sump.So I was thinking if I connect the 2 tubs together with pipe using the method we're speaking about, I'll feed the GB's with them also by putting a "T" in the middle of them so it drains into the GB's then in to the sump.The tubs are both drilled but on the bottom.So yes, I could let them drain with a stand pipe to a certain level on the inside of them and out the bottom BUT then how would I feed the GB's?So if I drill both tubs and connect them with the "T" to the GB's and then into the sump it would probably be my best bet.I'll use the bottom drains only for water changes etc or just cap them off.
Basically,as I said, it would look identical to that diagram except there's 2 FT's and 2 GB's and then to the sump.

You also have the option to plumb them together or you could simply split the feed from the pump to each fish tank and then have each fish tank drain to it's own grow bed where they both drain back to the sump. It all works. If you let them each drain to their own grow bed then getting the tanks perfectly level with each other isn't necessary but if you plumb them together the water level in them will have to be able to equalize so if one is lower than the other it will restrict the amount of water the higher one can hold without over flowing the lower one.

Just more options to think about, hope it doesn't confuse things.

I'm confused about the stand pipe in the GB. How is that set up?

Could you use a bell siphon in the GB?

Does the pump in the sump continuously run?

I'm sorry if these are noob question. I really suck when it comes to building things on my own (such as aquaponics systems).

no worries tumbling wheels..
depending on how you pump the water the standpipe can be just a standpipe set to a level about an inch below the surface of the media and run constant flooded, or put the pump on a timer, add a small hole at the base of the standpipe, your growbed will fill, but the additional hole (or holes) will allow the gb to drain..

or you can use a bell siphon, or an aphnan siphon..

there's a thread showing results for the different methods here:
http://www.backyardaquaponics.com/forum/viewtopic.php?f=1&t=8621
it can be a bit intimidating when you first start building if you haven't done it before, but after a while, your confidence will go up as you make progress.. lots of info on the forums and lots of folks will help - take lots of pics!

If you design the stand pipe so that you can pull it out and adjust the holes or flip it for a constant flood even be able to add a bell over it and turn it into a bell siphon you will have all options on your side.

I am only just come to understand how bell siphons work regarding resistance like being able to speed them up and slow them down etc

applying these concepts to venturis is totally beyond me, anyone got a simple explanation or a link?

I'm not sure I understand, how would you combine a siphon and a venturi? Any restriction of the water flow at the outlet of a siphon can mess with it's operation and trying to add an air inlet at the top of the siphon is likely to leave you with a constantly flooded bed cause the siphon wouldn't be able to manage the suction needed.

sorry, I just meant applying kind of general physics/plumbing concepts not those specific to syphons.

although there are plenty of diagrams of venturis I can't (I wish I could) figure out how it works entirely... again sorry Im really not trying to be ambiguous lol

It depends on the source of the venturi as to where to locate the inlet into the water flow. Adding any type of hole to the main part of the siphon will allow air in at the wrong point and create a continuous siphon break and it will never work. You can route a line from this hole to water at some point to close it back up for usefulness as an air break.

To add air to the siphon output, the venturi must be past the low water level of the siphon on the outside pipe. I tried removing the initial trapped siphon air as a venturi back into the output line but it did not improve siphon functioning. A one way air valve worked just as good/bad with no real improvement over not having them at all.

If you have a powerhead(pump) with a built in venturi line, you can connect this to your trapped air in the siphon or no holes overflow and it will constantly ensure that air is removed from it. Works great to ensure no holes overflows stay working and may help improve siphon starting (so long as power stays on).

Not sure that is the info you wanted but here is a good start if you want to take it from the beginning: http://en.wikipedia.org/wiki/Venturi_effect