Irrigation, Drainage, and Sump Setups for Aquaponics Systems
Today we’re discussing irrigation, drainage and sumps systems: design philosophy, techniques, and materials used in these systems.
Irrigation, drainage, and sumps are often overlooked in system design. People think about how they will be growing plants, but not so much about how they’re going to plumb everything together. Your plumbing is crucial to keeping oxygen flowing through your system, keeping healthy nutrients in your system, and delivering waste to your plants to be processed.
If you’ve listened to this podcast be fore, you probably know that our design philosophy centers around a split flow or “CHOP” design, with a sump in the ground and an inline pump beside that tank that pulls from the bottom of that sump tank. The pump send some of that water to the plants and some to the fish- split flow. Everything drains back to that sump tank. At the end of an hour, the water has been turned over twice, part sent to the plants and part sent to the fish. This ensures that most of our water has been filtered by the plants before it gets sent to the fish. If you are still confused about split flow, definitely look it up and listen to some previous podcast episodes.
Our second design philosophy is that everything operates better under pressure. If you have enough pressure to blow lines out and to introduce fast flows, you will keep your fish happy and make it easier on yourself.
The last thing to know is that drainage systems and irrigation systems are as much an art as they are a science. If you’re doing this on a budget, you will probably be designing this system yourself. Because you don’t have a team of engineers crunching numbers, determining pump size and pipe size for you, and a lot of these technical chores, you’ll basically be guessing a lot of the time. There are some rules of thumb, however, that can help you be successful right off the bat.
In irrigation you can use timers, solenoids to determine when and where the water is going, how much of it is flowing, etc. On thing to remember with timers is that pumps do not like hard starts and stops. Especially in inline pumps or larger pumps, sudden starts and stops can be really hard on a motor and cut down on it’s lifespan.
Pressure is really important. If you under-deliver pressure, there’s not much you can do. If you over-deliver pressure, you can use regulators like fittings and valves. These don’t have to be high tech. I will say this with the caveat that a lot of people really oversize pumps, and while a little bit of extra pressure isn’t a bad thing, a lot of extra pressure means that you’re spending too much money on your pump, and way more money to run it.
The extra pressure applies also to the sizing of your pumps. Sizing down a little bit is ok, but sizing up is not a good idea. You’ll have higher flow rates through larger diameter pipes- there won’t be a cap on flow.
In our system we have 1 inch poly pipe that’s the main and off of that main we half inch risers. Each riser serves a zone. It has a valve on it to adjust flow. We use fittings to direct water to the tops of our towers. With hard PVC they’re usually slip fittings, which are durable and easy. For poly tubing, we use barbed or compression fittings. With compression fitting, the pipe is squeezed as is goes through a collar, and then when the line is pressurized is secures the fitting. Barbed fittings are punched into the inside of a pipe. We secure barbed fittings with pipe clamps. The reason for this is that poly tubing is black, and it tends to heat up in the sun if water isn’t flowing through. You can turn off a zone and leave it for an hour, and the heat from the sun will heat that line up and kill anything in it. The downside to this is that as the tubing heats up it softens, and there’s a chance that under pressure, the line could pop off and spray water everywhere. (That has happened to me several times.) It took a couple of disasters for me to learn to use hose clamps on everything. One thing to keep in mind is that every time you have a hard turn, a T or and L in your line, you’re losing friction, pressure, and you’re losing flow at the end of your line. That reduces the efficiency of your system. So whenever possible we curve that tubing using a heat gun and molding it into a softer angle to reduce our friction loss.
Most systems are gravity-flow drainage. Probably 95% of systems out there use pressure in irrigation and gravity flow in drainage. People with multiple pumps or undersized pipes usually have some kind of assisted flow. If you don’t have enough elevation between the point you’re draining from and the point your’e draining to, then you often have to use assisted flow. We avoid this because it introduces another point at which your system can fail.
We drain out of our fish tanks using an SLO. I highly recommend using an SLO. (We have more information on SLOs if you’re interested.) A covered SLO is essentially a siphon, which uses the weight of the water to pull water down the pipe. A lot of people use siphons in ebb and flow or to drain media beds. You have to be really careful of siphons because once they form they will drain your tank.
We use hard PVC and polytubing as much as possible because it’s cheap, flexible, and allows us to do a lot of things we can’t do with PVC. Hard PVC is good when you need pressure or when it’s going to be treated roughly (get stepped on, etc.). The one thing I will say is that a lot of people have started using white poly. Black poly is still a lot cheaper, and the heating up aspect is something you want to keep for sanitation reasons.
Sizing your pipe can be an issue when you’re starting. Start with the diameter that your pump is built for. For example, if you have a 1/2 horse pump it probably comes with a 2 inch inflow and outflow. So you start with a 2 inch outflow and you split it. You can stick with the 2 inch to the fish, then split it to 1 1/2 inch to each individual tank. We deliver with high enough pressure that we don’t have to go much smaller. On the other side we split it to three 1-inch lines.
Sizing a pump to your system can be a tricky task. You will need to know how often you want to turn over your system, the number of gallons in your system, and of course your head height. There area lot of pumps like diaphragm that will deliver low volumes at high pressure, more traditional pumps that will deliver high volumes at low pressure (these are your inline pumps or submersibles) and pumps that are right in between. Match the pump to the application- know what you need.
Most people operate in 110, 120 volt service, so you’ll be plugging the pump into a outlet probably. If you have the option for a higher voltage, go with it. It can be really nice, especially if you are using a bigger pump.
Plumbing is hard to talk about since it’s a visual topic, but if nothing else, hopefully this has given you a good introduction and a good point to start from so you can go look up these topics.
Thanks for tuning in. Don’t miss our next episode, in which we’ll be talking about the basics of the nitrogen cycle in detail.
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