Backyard Aquaponics
A place to discuss aquaponics

The head up to top of elevated FT will be 9-10 feet. Probably a little higher then necessary. I am somewhat concerned about having adequate volume and "pressure" from gravity flow out of FT down to GB's.

What is the max/ min flow of water into 1oo gallon GB for constant flood?

Lets say its 2 gpm times twenty tanks, will require 40+ gpm pump from raft/sump tank. Energy use may be higher then anticipated.

Ideas anyone?

Whatever you decide to do, create a backup system to go with the rest of the system setup.
I've been reading this forum for a while now. Most everyone wishes they had installed one right from the start, usually right after their first HSM, or their second...

Thanks Bill, I had not thought of that. I think I will have room a back up system.

Rupe, I went and measured it. 2.5 meters from ground upto top edge of tank. 8.5 feet for US.

What are the dimensions of that raft bed Jdphish??

What should they be? I haven't built it yet. I am thinking 4 feet wide, 24 feet long, maybe 12 inches deep. I want it low enough to drain GB's into it, with enough volume to prevent serious depth fluctuations as a sump tank. I should be able to make it out of 6-7 sheets of plywood.

Trying to work out what size pipe you'll need to get enough flow to the growbeds... to turn over the volume of your fish tank at least once per hour...

But my brain hurts... need sleep...

But i figure you're going to need at least 100mm pipe... and probably at least a 15,000L/h pump ... but I could be way out...

If my FT is 1000 gallons or 3785 liters divided by 60 minutes per hour equals ~17 gpm or 63 L/m (3785 L/h). Thats 0.85 gpm (3.2L/h) to each 100 gal (378.5 L) GB. Is that enough flow with constant flood? Is low DO a concern in GB?

I am open to any questions and comments.

Here is a handy chart showing gpm flow based on various pipe sizes and pressures. Even shows gravity flow. http://flexpvc.com/WaterFlowBasedOnPipeSize.shtml

If the system is built as shown in my (EB's) sketchup with the elevated tank gravity feeding the GB's, the flow will be dictated by the pump. To much flow from the pump could possibly overflow the growbeds, leading to a pump running dry. The amount of flow through the gravity fed supply pipe and the volume each grow bed can "absorb" will determine the maximum size pump. I think?

Anyone else see it this way?

That's the kind of formula and maths I was scratching my head about Jd...

You're going to have to adjust your flow into the grow beds with a ball valve on each outlet anyway... to get the inflow right for siphon initiation... or even if you intend constant flood...

Instead of capping the end of the main distribution pipe... you could always plumb it with an overflow back into the sump...

That way it wont matter so much if the pump is a bit over-sized...

I still think you'll need at a pump at least 6,000L/H... and probably 100mm pipe... or two of...

Ok thanks Rupe, I intend to put a ball valve at each GB inlet pipe to adjust flow.

I considered an overflow pipe into the sump tank. My plan was to share the floating raft tank as a sump tank (the low green topped rectangle in sketchup). I was trying to avoid dumping solids into the floating raft/sump tank. If I put the overflow at the end of the pipe circuit, most of the solids will have settled into the low part of the pipe. The lowest part of the gravity feed pipe should be where it feeds into the growbeds.

Its gonna take a lot of work to put the system together...trying to avoid major screwups. I appreciate your input.

Managed getting a crappy shot of the 8 foot diameter, 1000 gallon fish tank. I don't especially like the idea of it being elevated for rearing fish. As a gravity fed water supply, it will be good. I built the whole elevated stand about ten years ago for an aquaculture project. The main uprights are 10 inch I-beams, with lots of bracing. The wood floor is 2 inch pressure treated pine. The existing standpipe and drain are six inch sch 40 PVC. Should get enough flow through those parts. Another example of the double decker GB tanks are shown in the right of the picture. When split, they should be about waist high.

The yellow "ruler" leaning against the other stand is six feet tall, as a reference. Yes, the greenhouse needs recoving, the wind finally got my 1 year white plastic after 3 years. New plastic is clear. Its a bit of a mess at the moment. I think it has potential. Also, plan on welding up a stairway upto the fish tank, with maybe a mirror suspended over the tank for easy viewing. Too many plans, not enough time.

Does anyone beside myself think this (shown in above sketchup) general AP plan is workable?

After reading alot more on this forum, I am nearly ready to eliminate the elevated fish tank from the system plan. Or just use it temporarily. EB recently said that the simplest setup is having fish tank below the GB level with one pump. Or at least thats how I interpreted it. One thing weighing heavy on my mind is the probability that the FT will get too hot in the greenhouse during summer months. Since the greenhouse has a concrete floor, an external fish tank (pond) dug into the ground (lined) just behind the wall shown in elevated tank pic may work. It would have a cooling effect during summer as well. Also, the in ground tank could be enclosed easily enough with a lean to type structure off the common greenhouse wall. Any and all suggestions would be appreciated.
Cheers,
Jd

won't any cooling effect from the buried tank be negated by pumping through the grow beds

I am not really certain. Good question. I was thinking of using a greater volume in a the buried FT. Seems anything would be an improvement over having a tank in the upper level of greenhouse during hottest times of year. Hopefully plant growth will offer a bit of GB shading (maybe wishful thinking. My experience with the elevated tank in my aquaculture application seems to support the rather elevated passive heating of the water. The only way I had to cool the temp was by adding 55 degree well water to the system during daylight hours. An in ground fish tank should have a relative cooling effect. Maybe someone can address the thermal dynamics involved. Thanks toddscat.