Backyard Aquaponics
A place to discuss aquaponics

Ok, there comes a point in time when you have to throw your hands up and appeal to the greater knowledge for help....I passed that point about 14 hours ago! Allow me to explain my situation and PLEASE interject with any advice if you feel the urge.
I just got my hands on a 180Gal insulated stainless steel bulk tank previously used to store milk on a dairy farm ( SCORE! ). This is a rectangular tank with a round bottom and is pitched to a 1-1/4 inch brass drain on one end. Since it is still too cold to start plants (could only fit this tank in my unheated garage) here in NE PA, I have decided to include a clarifier and trickle filter to get fish started ASAP without the grow beds. So I set it up just to test the configuration... ...This is where I start pulling out my hair! The clarifier is a 20 Gal high tank, emptying drain on the bottom, drilled overflow about 4 inches down from the top, and is filled with orchard netting. This tank has a free-floating standpipe in the center that is supposed to receive water from the fish tank drain, by way of an external 1-1/4 inch standpipe overflow and deliver it to the bottom of the clarifier where the solids can collect. No matter what I do, I cannot get a decent flow rate into the clarifier from this setup. Not even enough to keep up with my 235Gal/hr pump with a ½ inch return line. So, next step, I raise the clarifier to match it’s overflow with the desired fish tank water level in put in a 1-1/4 inch siphon from tank top to tank top…..same results. What am I missing here? HELP!

Hi TN:
Are you saying that the drain from the bottom of the tank to the clarifier is too slow to keep the clarifier full because the little pump is out flowing it?

DD: Correct, the 1-1/4 inch pipe ( either standpipe or siphon) will not fully flow, trickling to the point that it will not even keep up with the return flow from the pump. At first I thought the bulk tank just needed time to surge so I switched the sump to a 28 Gal tub, the pump will almost drain the tub before the overflow even starts. I started the system by filling the tank to the overflow point, then filled the clarifier to the overflow point so the water levels should be correct.

Is there some kind of valve on the drain?

My drain pipe was 1 1/4 but now is 2"; one thing I had going on was that too many right angles slowed down the flow a lot, the other was to eliminate any air bubbles (which it looks like you have, unless there is one stuck somehow in the section under the tank).

So the slow one is the overflow drain and the siphon? Where does the pump go in? Is it in the clarifier to return water to the tank?

There is a valve at the bottom of the tank (fully open). I have 1 - 90 elbow at the bottom by the valve and a T at the top of the standpipe. I did consider sweep elbows but did not get out to get them yet. The pictures do not show it but there is a 28 Gal sump after the clarifier. The clarifier has a straight pipe bulkhead at the water line that dumps into a trickle filter sitting in the sump; this is where the pump is located. Here is the flow steps: From bulk tank thru bottom valve, 90 elbow, up to water level (there is a T here with top open to prevent a full tank siphon), and into clarifier. Down to bottom of clarifier center pipe (free flow, gravity), up thru orchard netting to clarifier overflow. Thru overflow to trickle filter, to sump, back to bulk tank. Then I added the "U" siphon to try to help maintain flow to the clarifier. This was not my initial design; I wanted all water to flow from the bulk tank bottom to pick up the solids. Can I make this any more confusing? Would more pictures help? I am fully open to redesigns too if anyone has a suggestion.

Diagrams/sketches of the design would help. I'm lost.

Yeah, I'm a little lost myself, sketches would certainly help..

I'll put some together and post tomorrow, thanks

So if you let the pump keep going (if it had enough water to) would the milk tank overflow because the pipes are that slow?

I would think that even if there is a lot of resistance because of bends etc. that eventually you would pile up enough water weight in the milk tank to overcome the resistance.

If you loop the pump hose from the sump up to the top of the clarifier (like water coming in from the overflow), do you run into flow problems (like the clarifier overflowing)? My bet is that it is the flow between the clarifier and the sump that is slower than the pump... Just guessing though!

Would lowering the clarifer and lengthening the pipe from the mill tank giving more *head room* and greater pressure, improve flow. A guesstimation from this newbie.

OK, i think i know what the problem is.

does you clarifier look / work the same way that the gravel bucket in Steve&anges system does? Top left hand corner of picture............bucket is fed via the vertical pipe from the right, water trickles down gravel, to a sealed stand pipe in the center with 6mm holes drilled in it.

We have the same problem, the in flow rate can only be a very slow rate. or the bucket will over flow.

If it is the same thing then here are a few points.

bucket hight will have no bearing on flow rate UNLESS outflow fills and seals outlet pipe (which is doesn't)

slow flow is a combination of number and size of holes drilled in stand pipe, AND type and amount of "fill" material

flow will probably get worse as fill media traps solids.

So, basically i've not given you a solution, because i don't have one

In Steve&Anges application it does its job well. Its filled with gravel to act as a bio and solids filter ("virtual" grow bed). Water from the outlet flows down their 13m NFT pipe and then trickles back to the fish tank.

Hope our findings help you in some way.

I appreciate all the comments!

I quickly sketched my original design and the last two modifications.

Design1 is the original: fish tank to clarifier, clarifier to sump, back to fish tank. The pipe going from the bottom of the fish tank to the clarifier is where I am having trouble. It is a vented external standpipe overflow ( 1-1/4 pvc ). It will not flow full and cannot keep up with a 235g/h pump.

In Design2, I shortened the clarifier end of the tank overflow and added a larger diameter pipe to direct the solids to the bottom of the clarifier. My thought was that there might be too much back pressure in the overflow pipe to "push" the water down.

Design3 is the same with the addition of a "U" shaped siphon to try to equalize the water level from tank to clarifier.

From the tank to the clarifier is where the trouble is, just not enough flow.

The overflow from the clarifier to the sump works like a charm.

I was looking for a single pump design, that could fit under an 8ft height structure, and can maintain a population of fish with or without plants. Not too much to ask, right?

At this point I am thinking about putting a 4ftx4ftx1.5ft gravel bed above the tank and pumping up to it. Plants or no plants right now, this might still be the better idea.

does it work better if the vented top of the pipe is closed off?

My 1st step (if you haven't done this already) is to remove everything out of the clarifier (the media gunk/orchard netting) - this will check that the piping alone is large enough to take the water flow from the pump.

This will locate what area you should be working on, pipe size, pump size or orchard netting - get back to us on the outcome

System update: Last night I pulled everything apart (again) and reworked the whole system. Knowing that I will eventually put in grow beds, I decided to switch to a pumped outflow and gravity inflow setup. I had an IBC in a metal crate lying around and an old boiler circulator pump (1/25hp) that was used on a previous aquaculture adventure.

Here is what I did: I cut the IBC, 16” from the bottom and discarded the top. This is the grow bed with a nice 2” drain. I then put 2”x4” lumber thru the metal crate at 37” height (to create a shelf). I then placed the bottom of the IBC back in the crate on these 2”x4”s which suspended it so that the bottom of the IBC was about 2” higher than the top of the fish tank. Direct connected the pump to the bottom drain of the fish tank and ran ¾” flexible tubing up into the IBC. I do not have enough gravel to fill the IBC yet so for now I have the clarifier and trickle filter up there. I then ran a 2” drain pipe from the IBC back into the fish tank. So far so good! Woke up this morning, no floods, nothing has run dry, and nothing has collapsed!