Backyard Aquaponics
A place to discuss aquaponics

Regardless Scott... whether you're using auto-siphons or an overflow standpipe... you will probably have to adjust the flow into each bed to either set the flood level and/or trigger the siphon...

Just plumb a ball valve into each growbed feed line... and adjust accordingly...

Also means you can turn off the delivery to any bed, for any required maintenance...

We haven't got any ball valves as yet. We're using 40mm (I think) PVC pipe from the bulkhead fitting on the FT. The PVC runs down to the first GB, where there's a T joint, and then continues to the 2nd GB where there's a 90deg elbow.

We've adjusted the flows by rotating the first T joint. If it's pointing down, then the first GB gets almost all of the water. Horizontal, hardly anything.

It's not the best solution, but workable for now. Both siphons are stopping and starting reliably last I heard.

Thanks for the prompt replies...

It has given me some things to think about.



Scott

One thing I was a little surprised at was how low the flow is when the water's not under pressure. We're glad we went for a fairly large diameter pipe for the overflow, in hindsight it's only just big enough.

The flow into the tank is via 19mm (?) black pipe, and the 40mm overflow seems to struggle a bit to keep up.

I have found this an invaluable source of information: It's from the manufacturer of the PVC pipes most(?) people here use.

http://www.vinidex.com.au/files//technical_notes/Flowcharts/vin015_pvc_flow_charts_250808_email.pdf


Hope it helps.


Scott

Yeah, I am using 40mm for my IBC Trout tanks, and I had to convert them from gravity to siphon to make them flow enough.

Yes, very large pipe is needed for gravity feed in relation to the same flow pressure fed.

I've also learned that if you have a pump that seems to be having difficulty giving enough flow, before buying a new pump, you can first try hooking it to larger plumbing and it might suddenly be powerful enough (though you would then need even larger drain plumbing to deal with added flow.) Even if a pump is supplied with 19 mm threads, hooking it to 19 mm pipe might not be the best way to get the most out of that pump. I lately adapted a pump with 19 mm threads up to feed 40 mm pipe and suddenly that pump seems far more powerful than it's small size suggested.

The trick of twisting the fittings to get even flow to the beds is quite good actually. Since you are going gravity feed out to the beds and you mention that the 40 mm pipe is only barley enough for the flow, adding ball valves might restrict your flow too much.

My first setup was similar to your except that I had 5 small beds and I controlled the flow into each by drilling more holes into the pipes or stopping up holes. Because of the very low pressure I always struggled to get them filling about the same rate and if too much gunk built on it could block the holes or if the pipe moved (thanks kids) it would completely upset the balance.
That's why I gave up on the gravity feed and am building a new system.
Because you're using a siphon drain your pump is running all the time isn't it? Why not create a manifold with 3 valves and direct 2/3 of the water to the GB's and 1/3 to the FT with the FT overflowing back into the sump. This way you can use your pump at full speed without worrying about overflowing the FT because it will only get a third of the flow instead of all of it.

I would say leave the feed to the grow beds as they are and if there is too much flow into the fish tank causing worry about overflowing, just plumb a bypass from the pump to divert some flow back to the sump tank.

I don't like sending water from fish tank back to sump since that can promote solids build up in the sump tank. Solids build up has been the source of problems and fish deaths in many situations. Ya want the solids to get to the grow beds in as efficient a manner as possible (that is unless you are going to do some sort of solids removal on a regular (read daily or at least every 72 hours) basis.

If the pump is running continuously, isn't there a good chance that the solids arriving back at the sump would have a 66% chance of being pumped to the GB very soon? I'm building this into my new system...if it's not going to work I'd like to know.

I suppose the theory is that the solids stay in the GBs, and should never appear in the sump.

Right Curly but Monkeypuncher is talking about pumping from the sump up to the grow beds and to the fish tank and having the fish tank overflow back to the sump instead of into the grow beds. This would leave the only rout for the solids to get to the grow beds as being through the pump. It can work and some people do it, however the solids once they have been blended up by the pump, don't always stay in the grow beds as well as intact solids. Smaller continuous running pumps sometimes don't stir/suck up solids as well as one might hope. An air stone would definitely be needed to help keep the solids moving on out of the sump, especially without any fish in there to help stir up what solids are collecting to get the pump to pick them up. And the drawback of having to pump solids meaning that more pump/pipe cleaning might be needed.

As I said, you can do it that way but I much prefer how Dave's system is currently set up with the fish tank gravity feeding the grow beds and the sump being a clean water environment.

An option would be to use the common stand pipe with drain hole arrangement (ala timed flood and drain) with a siphon (with continuous pumping) in the same GB. As long as the top of the stand pipe is higher than highest point of the siphon or the point at which the siphon kicks in so it will always starts. Having a drain hole you also slow down the fill rate of your grow bed.
This is how I have been planning (on paper so far) my IBC system.

So for example;
1000L FT
2 x 500L GBs (with 400L total water holding capacity for examples sake)
1000 L/h pump (turn over FT volume every hour)

Looking at each GB individually, every hour 500L of FT water flows in. So you want a hole that will allow 300L to pass through it (in a perfect world) in 1 hour.
Therefore after 1 hour 200L will have been trapped in the GB and start the siphon/flout/flush valve to quickly drain the GB.
Advantages here are 1, if the siphon doesn’t start for whatever reason (not sure if bell siphons do this?) the stand pipe will just let excess water flow back to the sump and not over flow your GB and 2, no throttling of the pump is required.

The small drain hole could be replaced with a tap out the side of the GB (with appropriate screening from media on the inside to avoid blocking) so we have more accurate control of out flow instead drilling or plugging up holes in the stand pipe. This may be needed as root mass increases in GB’s and cause them to fill faster (just a thought not sure if this actually happens). Advantage here is you’ve got control over how fast or slow you GB floods, anywhere over 24min being 500 L/h into 200L with the tap off (or no drain hole).

Any thoughts?

Won't the roots be flooded almost all the time under that scenario?

it will take an hour to fill and then drain quickly. So slow fill fast drain.
This scenario is often questioned as to which is best, fast fill slow drain v's slow fill fast drain. Both achieve the same thing it seems.