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WARNING! Ebb and flow design flaw in slow flow in fast out
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Author:  Aquaddict [ Jan 14th, '07, 10:27 ]
Post subject:  WARNING! Ebb and flow design flaw in slow flow in fast out
I've given this it's own topic so it's not buried in my greenhouse thread.

My bed was not draining correctly, staying half full as water running out the drain was going out faster than it was draining into the standpipe.

So I dug out the gravel to 'fix' the standpipe. Every inch saw more and more roots till for the last 4 inches they were so thick I confidently just slipped the pipe out and there remained a solid circle of roots in which I can remove and replace the standpipe with ease.

THERE WAS NOTHING WRONG WITH THE STANDPIPE , IT WAS MY DESIGN

The root mat was the problem, you can't have a healthy growbed without a healthy root mat.

Therefore - it is a design problem. After the bed is full of roots the flow through them is considerably slower. I tried to auto siphon without the pipe in. Same thing. - Water drained out of the circle of roots faster than the bed fed the remaining water into the gap.

This is now a continuous flow bed... :lol:

If I explained this badly tell me so, I'll try clarify.
Author:  steve [ Jan 14th, '07, 10:34 ]
Post subject: 
i think i understood it ring, i had a simmilar teething problem with my bed, but not becasue of roots. the water would drain out of my auto syphon inner quicker than the bed water you come through the stand pipe, ending with the syphon breaking and then the backlog of water still being there. I fixed it by making innovative "crella-whatsis-thingies" cut outs. will post a pic. PS les, system is still working a treat with no air bleed. ;)
Author:  RupertofOZ [ Jan 14th, '07, 10:35 ]
Post subject: 
How old is the bed AA and what have you had growing in it...

Was it always "flood and drain" with a siphon or just drained by flow through holes in the standpipe?

Were you pumping continously or on a timer cycle?
Author:  GotFish? [ Jan 14th, '07, 10:39 ]
Post subject: 
AA, How was your syphon set up? I'd think a root ball would just create more mass in the grow bed thereby less water would be needed to meet the syphon starting point.
Author:  Aquaddict [ Jan 14th, '07, 11:01 ]
Post subject:  Re: WARNING! Ebb and flow design flaw in slow flow in fast o
Here's a picture. It's just a looped auto siphon in a standpipe.

I wanted to use a small pump to conserve power.

This is a slow flow in, fast out, and fatally flawed for large plants.

Even without the standpipe, the siphon drains faster than the bed supplies the water, this then shuts off the siphon early, and the water level in the bed is nowhere near empty.

The problem isn't starting the siphon, it is that the siphon stops early, even no siphon, merely the remaining tube of roots, did not flow fast enough to keep the 13mm drain occupied. The roots slow the flow and it won't drain out fully, this causes stagnant water, lower DO in both bed and pond, and a whole bunch of what I really hope are wee mossies, not nematodes, in the remaining bed water.

Attachments:
Pumpkintakingover (Medium).JPG
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Author:  Aquaddict [ Jan 14th, '07, 11:02 ]
Post subject: 
No timer, I was trying to remove parts from the design.
Author:  GotFish? [ Jan 14th, '07, 11:03 ]
Post subject: 
OK I understand now.
Author:  GotFish? [ Jan 14th, '07, 11:11 ]
Post subject: 
My beds dont always drain out completly, (system design) its dependant on the timing of the header tank syphon start in relation to the grow bed syphon start. I flood around four times each hour so I think low DO and such is not a problem that I could have and for me a root ball would just add to the mass of the grow bed. (scratches head) In theory?
Author:  Aquaddict [ Jan 14th, '07, 15:33 ]
Post subject: 
My pond just cleared in... (checks time of warning post) 5 hours!

It was silty and a bit smelly. Now I can see the bottom and the fish are up waiting for food when I enter.

Go go continuous flow!

Another perfect day in AP ;)
Author:  Dave Donley [ Jan 17th, '07, 01:40 ]
Post subject: 
Hey AA:
Do you think adding compost worms to the grow beds would keep the roots at bay enough to function like it should?
Author:  Aquaddict [ Jan 17th, '07, 03:13 ]
Post subject: 
I hoped to find evidence of said worms (I've added earth and tiger worms) in the bottom, it is just roots. Roots so thick you can't see any gravel for the last 10 cm's where the standpipe slides in and out. Even the continuous flow had to be throttled back by half to stop the bed filling faster than the roots allow it to drain.

There was 1 cm water in standpipe constantly draining, and 20 cm's in the bed...
Author:  janethesselberth [ Jan 17th, '07, 03:33 ]
Post subject: 
If they are live healthy roots, the worms would not bother them anyway.
Author:  bhsx [ Jan 17th, '07, 04:46 ]
Post subject: 
What can be done to fix it?
Would a horizontal pipe at the bottom of the GB, attached to your standpipe help keep the flow going?
That's the first thing that popped into my head.
Perhaps even lose the stand-pipe and have a long horizontal pipe covering your siphon? Actually, I'd think a pipe cut vertically (half-pipe) covering the siphon might be a good answer, as you'll be counting on the downward force of gravity rather than path of least resistance for your waterflow.
Author:  Aquaddict [ Jan 17th, '07, 06:04 ]
Post subject: 
What would fix it would be slower flow out ie, the original ebb and flow like others do, I had to try, it might've saved us a lot of power.

I prefer continuous flow anyway, just fell in love with auto siphons they're so cool.

Continuous flow grows faster than ebb and flow, even Joel'll tell you that. Can't remember chaps name but 3 years research spent netted same result - continuous flow 20% faster than ebb and flow.

Now I'm in trouble.....
Author:  bhsx [ Jan 17th, '07, 06:24 ]
Post subject: 
I understand completely what you were going for with the fast-drain. It makes sense, and generally what I've been thinking of doing in an S&S style system, so I do hope a solution can be found. I wouldn't think that you somehow stumbled across a flaw that's unique to your circumstance, I agree it's a flaw in the design. Hopefully, it's a flaw that can be overcome. Good luck.

I got the bug pretty bad and have sooooo many designs to test out, and play with; but I love the "idea" of the S&S system, especially combined with low-power lifting.
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