Backyard Aquaponics
A place to discuss aquaponics

Ok so I've been building my first system and now it is time to plumb in and I have some questions. The system is a small CHIFT PIST with a 35 gallon FT.

1. How big should my plumbing from my pump be? Is it OK if its larger than the size coming from the pump outlet? Right now I'm planning on it being 3/4" and the pump outlet will probably be around 1/2".

2. For a bell siphon how big should the stand pipe be in relation to the input into the GBs? How big should the siphon pipe be in relation to the stand pipe? Is there a specific ratio that I need to follow to get the desired suction or simply a minimum size? Does the siphon pipe need anything to attach to the bottom of the GB or does it stay put because of the suction?

As of right now the plan is to have a 3/4" input with a 3/4" standpipe. I came up with this based on the chart from the auto-siphon wiki page, but I'm beginning to thing I should switch to a 1 1/2" standpipe with a larger diameter (3"?) siphon pipe as I read a post somewhere saying the siphon pipe should be 100-200% larger than the GB input. Are there any other tips I should know about building a bell siphon?

1. it's certainly OK, and should the pump manufacturer not have got his efficiencies right, you may get better efficiency this way, especially if running the pipe any distance.

2. standpipe vs bell size is rather mathematical, but I'll try.

S = Stand pipe radius
B = bell Radius
G = gap between top of standpipe and top of bell.

I believe that the best siphon occurs when the volume of the pipe remains constant. So:

area of stand pipe = area of bell - area of stand pipe.

and

area of gap = area of standpipe.

so
As = pi x S^2

Ab = pi x B^2 - As
Ab = pi x B^2 - (pi x S^2)

area of the gap is calculate by the circumference X the height (h).

Ag = 2 x pi x S x h

As we stated that As = Ab = Ag then we have 3 simultaneous equations

A = pi x S^2
A = pi x B^2 - pi x S^2
A = 2 x pi x S x h

As pi is in all of the equations, it is cionsidered a constant, and therefore can be cancelled in proportional calcs

A ~ S^2
A ~ B^2 - S^2
A ~ 2 x S x h

so to calculate h and B

S^2 = B^2 - 1
s^2 = 2 x S x h

so
B^2 = 2 x S^2
B = sqrt(2 x S^2)
and
h = (S^2)/(2 x S)

so if using 20mm stand pipe (radius 10mm)

B = sqrt(200) = 14 (diameter 30mm)
h = 100/20 = 5mm

but these are just guidelines, you'll need to tweak. But it's a good place to start imho.

I would go with the 3/4" stand pipe since the pump output is really only meant to be 1/2"
At least I have been running a system that has a 3/4" standpipe bell siphon and the pump piping is 1/2" of course I am demanding a fair bit of head from that little pump so it is not a fast flow where it enters the grow bed at about 5' of head (Barrel ponics top bed converted to gravel flood and drain.)

However if you have really strong flow into the grow bed and really free flowing media, perhaps go for the thin wall 3/4" stand pipe or maybe you could go up to 1" stand pipe but I don't think 1 1/2" with the 3" bell would work very good for you in this situation.

I think the standpipe size will need to depend on the flow from the pump. I used a 300 GPH pump that had 1/2" outlet, adapted to 3/4" pipe, going into four beds of 25 gallons each, each with a 3/4" garden hose loop siphon and all four siphons worked fine. So your siphon and pipe sizes will depend on the flow out of the pump. You could put a bypass tee on the pump outlet with a valve to bleed off excess flow if needed.

Thanks for the replies! One more thing I'm not completely clear on. Does the bell siphon pipe need to be affixed to the bottom of the GB?

Also for my pump should I be more worried about the amount of lift it can provide or the gph?

Most outter pipes of bell siphons just sit on their crenelations on the bottom of the grow bed so you can lift them off easily if you need to.

as far as lift of GPH of the pump, you want a pump that can provide you enough gallons per hour at the head height you are expecting of it. often times the gph listed for a pump is at the minimal head. So often a pump listed as 500 gph with a max head of 20 feet will actually only pump 500 gph at a minimal head and at 20 feet it might not actually pump anything more than a dribble.

So, if you can find a pump that lists a chart or graph that shows how much it pumps at various heights, then you can see if it will pump enough for you. Say the top of water (Head height being measured from the level of the water not from the position of the pump) in the tank you are pumping from is a meter below where you are pumping to, then you want a pump that can deliver the capacity of your fish tank (or a bit more) a a meter head. Does this help?

Thanks for the help everyone! So far everything is going great. I went back to the irrigation store today and got what I needed and now my bell siphon works! I was also able to rig together a bunch of fittings so it plumbs in perfectly through the bottom of the GB. I'll post some pictures probably tomorrow. Now I need to get a pump and figure out what I'm going to do about my FT.

Ok so I've got a few more questions. First of all how high do I want to flood my GB's? I've read that the top of the gravel shouldn't get wet. How far does that put the water level below the rocks?

I also bought a pump. The one I settled on is a Jebao WP1500. It pumps quite a bit more water than I need but I was thinking I could turn down the output on it and have an excess water tube that feeds back into the sump tank to help with aeration for the fish. Also when I move up to a larger tank I don't want to have to get another pump so I got one that would give me some space to grow. Does anyone have experience with this pump?

I'm sure there are heaps with experience of this pump.
Shunt regulating water is the best way to extend pump life. Shunting water to the sump for aeration is great for AP.
flood to max 1" below the surface, it's possible to flood however low as you like, but the more is the better for bacteria and plants like to be able to reach the water

With shunting is there a preferred way to set up the ball valve? Should I place it on the line to the FT or on the shunt line?

the shunt valve should regulate waste flow. Flow to GB and ft should be unrestricted.
for efficiency reasons, one valve should ALWAYS be left open.
so if you have multiple beds, and you use valves to regulate flow to them, one should be open.
The valve on the line from pump back to sump (waste flow) will due to it's much lower head, pump a much higher volume, and therefore will require a valve to limit flow.

So I was just reading some information about the pump I got and I came across a site that said this about it: "
These pumps have no strainer and are suitable only for clean water type features. They are not intended for long term use in garden fish/waterplant ponds." Will this be a problem if my pump is in the sump? How wel do GB's filter water? Is there some way I can build a strainer/prefilter for the pump?

you can purchase basket filters from any good pump shop. This can go on the inlet to the pump, or the inlet to the sump.
But if it's a submersible pump you can't put it on the inlet.

A milk crate covered in shadecloth should do the trick.

How about dirt in the water? The gravel I'm using as a medium isn't very clean. Will pumping dirty/sandy water hurt the pump? I was thinking that instead of cleaning it off beforehand I could just cycle it and let the solids collect in the sump where I can easily remove them.