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Sunday, September 11, 2011

10 - Pumps, Plumbing, and Timers

How one pump can feed four growbeds

The only appliances you need in your aquaponics system are a water pump to circulate water and an air pump to keep up the levels of dissolved oxygen. I’ll discuss electrical pumps, since most folks have access to electricity, whether delivered by the power company or generated at home in some manner.

The water in your system should circulate completely once an hour. So if I have 200 gallons in my system, you might think a 200 gallon per hour (gph) pump is enough, right? Unfortunately, the flow rating on the box of a pump assumes there are no significant friction losses in the pipes and the water is only being pumped 1-2 feet up hill. Since I have 200+ gallons in this 365 Aquaponics system, I’d want at least a 500 gph pump. I’ve used 800 and 1000 gph pumps, which gives me plenty of power to overcome piping loss, intentional throttling, and bio-fouling (e.g., leaves and algae gumming up the works).

Most systems I’ve seen use plastic pipe or tubing to carry water from the pump to the grow beds and tanks. But these tend to be expensive and/or complicated. As someone trained in the physics of fluid flows, it hurts my soul to see right angles in water pipes. Right angles create friction losses and invite blockage.

Turns out there are all kinds of manifolds with valves designed for garden hose. You can buy them at your local hardware store. And they’re cheap, because tens of millions of people buy them. So far, so good. Regular garden hose, however, isn’t safe for drinking water due to the amount of lead it can leach into the water. Call me silly, but I don’t like leaching lead into the water my fish drink and breathe. So I use special ‘garden hose’ that is specifically designed for drinking water. If your local hardware store doesn’t have it in stock, you can special order it, or order it online. It’s not much more expensive than the stuff that leaches lead, and you can usually get it shipped for free if you shop around.

Draping the hose between the pump and grow bed is trivial for the growbeds on the same side as the sump. But it’s a bit more complex for the beds opposite the sump. Below is how I drape the hose, to ensure I don’t kink the hose, don’t block access to the garden, and put the hose opposite the end of the grow bed that drains into the sump or fish tank. Here is a video clip showing the water pump and hose installation.


Timers - If you have functioning bell siphons, you can leave the water pump running continuously. But there are reasons to have a simple timer to turn the water pump off and on:
  • Stopping water flow at night. You may do this because it's cold weather, and you want to conserve thermal energy rather that spending energy to "cool" your water by circulating it during the dark nights. Or you might just want to keep it quiet for your neighbors. Since I turn my pumps off at night, I have drilled a small hole in the standpipe of my bell siphon so any excess water remaining in the grow beds can drain when power goes off for the night.
  • You don't want to deal with bell siphons. In this case, you can set the timer to turn on for 15 minutes every so often (say once an hour). As long as you have a standpipe with a small hole at the bottom, your beds will fill while the pump is on, then slowly drain when the pump is turned off.
  • Even with functioning bell siphons, you can throttle back on power requirements by turning the power off intermittently. This can be particularly important if you have an extended power outage, and are trying to maintain your system off a small solar array.
There are any number of timer systems out there, but I believe a simple timer like the one pictured above will take care of most needs for an aquaponics system.

14 comments:

  1. The timer is used on the circulating pump when you know instant hot water will. The timer is used on the circulating pump when you know instant hot water will not be required. It save energy and money by not putting hot water into the line to cool off when it will not be used.plumbing company manchester

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    1. I love a semi-plausible spambot. Irene wasn't really credible, but she was sufficiently close I approved her post. Although the link to a plumbing company in manchester was a hint that this wasn't a standard post from a curious gardener.

      For those of you who are curious gardeners and who don't already know, I ended up getting tapped to write The Complete Idiot's Guide to Aquaponic Gardening for Penguin Book Group. The book is now available for purchase at Amazon.com. It includes lots of DIY plans as well as everything I wished I could have found in a book back when I was starting out (which wasn't very long ago...). So far the reviews are good!

      One of the things I put in the book is a DIY plan for creating a 15 minute timer using two inexpensive 30 minute timers (that is, timers you can turn on and off in 30 minute increments). Enjoy!

      Delete
  2. I think Irene Maranto is a spambot. At least I'm not sure how anyone who actually read this post could think I was talking about a pump in a hot water heater.

    On the other hand, I have been thinking about how to plumb up a solar hot water heater for the winter, using convection to "pump" the sun-warmed water into the fish tank, then a check valve to prevent the night-cooled water from siphoning back into the tank the opposite way. I've decided I love sharkbite plumbing fittings, copper tubing for the sun-exposed piping, and pex for the piping that runs through the fish tank... For fun!

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  3. Hi Meg. Copper is toxic to fish. ;-)

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    1. But pex is not toxic to fish. Neither the copper nor the fluid running through the copper would ever be in contact with the fish. The hot water would flow through pex tubing that loops around in the tank, then back out to the inlet of the copper tubing inside the solar heater.

      I suppose I should do a post about it with pictures and all, so folks don't get confused.

      Delete
  4. Could you explain your air pump system a little more?

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    1. Hi John,

      You can use an air pump to pump water by:

      1) Having tubing through which the air is pumped and

      2) Allowing water to "leak" into the air tube.

      With a small window farm, you can use a standard aquarium air pump and tubing looped down into a fish tank. Simply insert a plastic T-fitting near the bottom of the fish tank. As long as you have several inches (preferably a foot) of water above the bottom of the T-fitting, the water droplets will be shot up the tube several feet above the fish tank.

      Glenn Martinez in Hawaii uses a 40 watt air pump to push ~1000 gallons per hour in systems he's installed. He uses a 2 inch flapper valve to keep the water in place so the air coming in via a 1 inch pipe can propel slugs of water up the pipe. When you submerge this contraption by a couple of feet further below the surface of the water, you can get the slugs of water to shoot up tens of feet, allowing you to use a system like this to add water to a elevated water tank. Very cool stuff, actually.

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  5. Hi Meg, i've been bitten by the aquaponics bug, lol, i've just ordered that book off amazon. I'm looking to do a small scale one then go commercial somewhere in africa.

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    Replies
    1. Jay -

      Congratulations on getting bitten by the bug, and may you never fully recover :)

      Good luck with you dream of going commercial somewhere in Africa!

      Delete
  6. In as much as photosynthesis doesn't happen at night, is there any reason to circulate the water at night?

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  7. The reason to circulate water at night would be to oxygenate the water for the fish. As it happens, I keep my fish density sufficiently low that I don't worry turning the pumps off at night.

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  8. Please what pump model/make do you use or recommend

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  9. Where can I buy the four groebeds Pumps sockets? I need it fast. I stay in Malaysia, how it ship and payment?

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  10. Hi Loong Gor,

    If you're looking for pumps, I would suggest you check in stores that carry equipment for ponds or hydroponics. If you're looking for sockets, I'll just say I've used standard garden hose fittings, though I have used a special hose that is safe for potable drinking water.

    ReplyDelete