Backyard Aquaponics
A place to discuss aquaponics

I'm hoping to build my first system in the coming months, and I'm interested in a design with one pump that is constantly on, taking from a sump to fish tank, the fish tanks would have a low point from where the water would be drawn out and feed different grow beds each with its own bell siphon. It sounded like people have had issues with low-pressure indexing valves. And are the only type of indexing valves the ones that require temporary stop in flow? What about an indexing valve on a timer? It seems to me that using a timed low-pressure indexing valve, rather than a timer on the pump, would extend the pump life and still accomplish rotating between GBs. But then I'm a newbie...

I guess I should ask my question more clearly.

Have you had experience with low-pressure indexing valves? Do you use one on a timer, or one that requires a stop in flow to advance to the next outlet?

No experience whatsoever with indexing valves... but just thought I 'd ask... why do you need one?

Also, why pump out of your FT?... Why not also run a sump tank (ST) with enough capacity to account for the water required in all the GB's if the timing of all the siphons line up?... and pump from the ST to the GB's?

This way the water in the FT can remain at a constant level and you would most likely achieve cleaner water in the FT. The ST level would fluctuate as the GB's flood & drain, the water from the GB siphons would return to the FT, displacing water from the FT to the ST via a Solids Lifting Overflow (SLO) and picking up the fish waste solids from the FT as it does, therefore moving the fish waste into the ST.

This method would mean the only moving part in the system is the pump, which would be running 24/7 as you wanted. There would be no timers or indexing valves creating potential fail points, the water in your FT would be cleaner, and it would more than likely cause less wear on your pump.

I've just re-read your initial post and I imagine the diagram below is how you actually envisaged setting up the system.

That's an even better layout IMO than the diagram I included in my last post, in fact I think this layout is the optimum AP layout... but I have to ask again... why do you think you need an indexing valve?

This layout can be run perfectly well with multiple GB's, with a siphon in each... as long as your ST has the capacity to allow for the timing of all the siphons occasionally lining up and the GB's all being flooded at the same time.

I see in your drawings that you are assuming he is running a cut off IBC - by the way you drew your designs.
He may have 10 - 2.4m x 1.8m beds to drain, do you realise how big the sump would have to be to accommadate such a setup, especially if he has to dig his sump into the ground?

i think he has worked out he needs to drain one bed at a time or maybe 2 at the most.

Sorry i dont have any experience with indexing valves, but ill try do a quick search for you.

I havent been able to find any sort of valve with inbuilt timer or timer that can be fitted to a valve, the best i could think of right now, which isnt great, is to have 2 solenoids hooked up the the feed line in the sump and have one turn off when the other turns on - returning water to the sump for a little while, this poses mutliple problems though from vavles possibly not working because of gunk buildup or low pressure.
There is also the fact that im not sure if indexing valves will work when gravity fed and even if so, turn your pump off and your SLO will feed water to the valve for multiple minutes before it stops in a lot of cases, atleast will in a decent size system/FT.

I didn't assume anything about his chosen materials... They are simply drawings I already had on my computer... They simply represent the components and layouts of different designs.

Yes, I did alright in maths at school… but who would design a system with GB’s of that size & number and draw the water required for flooding them from the FT and not from a ST?... In fact who would design a system with 10 large GB’s?... It would make far more sense to make two or three smaller systems?

IMO it would be illogical to run 10 large GB’s in the one system, especially if the O.P. is planning on flooding and draining them one at a time…

Let's say for the sake of the discussion the O.P. has 10 GB's of the dimensions you mentioned, and wanted to F&D one at a time... for the amount of fish required in the system to provide adequate amounts of nutrient to such an area of GB’s, they simply wouldn’t be able to turn over, through the GB’s, the required volume of water from the FT per hour to meet the bio-filtration required… The numbers simply don’t add up... unless they had a pump and siphon that could F&D a 1300L GB in about 6 minutes... roughly.

Also, the O.P. has already stated they were intending to put a ST in the design and they never mentioned anything of burying it. There’s no reason, in either of the examples I provided, for the ST to be buried.

The OP hasn’t said that... Hence why I posed my question.

Thanks, Mr. Damage's drawings helped me understand how increasing the size of the ST can eliminate the need for an indexing valve, and eliminate one point of failure. I like the second design as well because it shortens the distance the fish waste has to travel to get to the GBs, and eliminates a place where it could accumulate.