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.