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Thread: Speed drain-fed scrubber

  1. #1

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    Speed drain-fed scrubber

    I know it is often encouraged that one use a dedicated pump for their scrubber, but I am running out of electrical real estate and I don't think my landlord would appreciate an overhaul of the wiring. So, I'm hoping that this is a good idea and that I can get some good insight into the whole thing by asking those who've already tried this. So, the plan is to feed the scrubber via the overflow. I know that the potential for clogging is a problem, but the new system I'm setting up (after being out of the hobby for about 8 months) will have a speed drain-style overflow. There will be 2 drilled bulkheads in a single corner overflow box. There will be a ball valve on the scrubber, allowing the water level in the overflow to rise to a certain, controllable level. As a safeguard, the extra unobstructed bulkhead fitting will be there to prevent any potential disasters if the scrubber were to clog and back everything up.

    The system in question will be a 40g breeder that I had before. I'm looking at a roughly 7-8" length of screen and about 8" or so tall, which should be more than covered by the added flow from the speed drain. I'm using a nice Tunze silence pump (the 600gph one, I think) that I had throttled on my previous small setup. I'll be using the previous little clamp-on fixtures and 40w CFLs that I had brand new in the box. This one will be a bit more modestly sized compared to my previous one, which was on the same tank. It did a little too well and I couldn't keep up with enough food to satisfy the needs of the scrubber.

    So, any input would be greatly appreciated. Please let me know if this is feasible or at least sounds reasonable, as well as any other tips, critiques, etc. In the meantime, I'll be looking at some of the designs so that I can implement some better splashguards, ease cleaning, etc.

  2. #2
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    What's a speed drain?

  3. #3

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    Oops, I should've clarified. Sorry about that. I don't know what they used to be called, as I used them many years ago, too, but they call them speed drains or "herbie" speed drains now. They were originally designed to feed more water into large skimmers and make a quiet overflow/reduce bubbles. Here's the general premise:



    When tweaked just right, the water level will be just below the safety drain and all the force of the water will go down into the scrubber (it also allows you to increase the flow from the return). If something causes a clog, the water is routed to the safety drain, which is the same size as the primary drain and can handle the water flow. These setups allow large quantities of water to go through the overflow, since they are considered full siphons.

  4. #4
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    I wouldn't have any drain at the bottom of the display.

  5. #5

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    Quote Originally Posted by SantaMonica View Post
    I wouldn't have any drain at the bottom of the display.
    It won't be at the bottom, but within a sealed overflow box.

  6. #6
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    I think he has it in the bottom of the overflow box.

    There is no big deal running a scrubber this way. I have not had a slot pipe get clogged. But theoretically, it can happen, if you have a fish/snail/anemone make it to the siphon intake and it gets sucked down to the scrubber. A snail could get wedged into any drain pipe for that matter and cause an overflow situation.

    A drain with an outlet that is open at the sump end does not have a worry for a (small) fish or anemone making it through - because it will make it through. The problem with a scrubber is that there is no large outlet - only a slot. So the fix is to not insert the screen all the way into the pipe. You need to suspend the screen from 2 points and make sure it only pokes up into the inside of the pipe a little bit. This will allow for room for anything that makes it's way all the way through to the slot pipe to get pushed freely to the end of the slot, leaving the water to pass through normally. This leaves you with the problem of how to get the buddy out of the end of the slot pipe, but leaves your tank not overflowing.

    For a non-siphon system, you can employ the use of a bypass standpipe such as this one that I proposed a while back:



    This type of arrangement, or something like it, allows for water pressure to build up over the slot, allowing the flow to keep under pressure and prevent algae from growing into the slot. But if the slot gets clogged, it backs up to the upper tee (right) and flows down a secondard outlet. The upper tee is near, but below the display tank water level, likely up the back of the tank. This does not work for a herbie / BeanAnimal full siphon line though as it breaks the siphon.

    Personally if I were to run a scrubber off a full siphon line I would make 100% sure that the second line could handle the full flow in a non-siphon mode. Better yet, run a BeanAnimal 3-pipe system and you're really safe then.

  7. #7

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    A third drain is doable. I may well incorporate one as a further failsafe, in addition to using some sreen to block potential unwanted guests from even making it into the overflow to start with. Even then, I wouldn't be shoving the large amounts of water through it you sometimes see. It would only be enough to power the scrubber.

    So beyond that, you think it should work out well enough?

  8. #8

  9. #9

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    Full beananimal design won't work for me, since I am restricted to a corner overflow box. A slight modification with an added third drain, however, should work well enough. 2 of these extra drains should handle about 600 gph, which is more than what I'd be running through it.

  10. #10
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    Here is how I do it to avoid clogging/overflowing of the tank using an ATS fed via the overflow. Nice to see my 'mentor' over here.


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