Introduction: Making and Deploying a Check Valve for a Hydroponics Multi-tier Flood-and-drain Rig
This instructable describes how to:
- Make a “check valves”, like the one above, and
- Use it to construct a multi-tiered flood-and-drain hydroponics system that is served by a single pump.
A check valve is one that will allow liquids to flow in one direction only. We’ll make a special type of check valve that uses a floating ball as a component. We'll configure this valve so that it allows water to flow downwards, but not upwards. After you make the valve, you install it in your system, using appropriate adapters to make it fit.
Note that this instructable does not describe how to make any other components of a hydroponics rig, nor how to assemble one. There are many ways to build a hydroponics system. (Just search Instructables, and the Web!) The check valve is simply a component that allows one way of making a tiered flood-and-drain system. You can also use it to convert an existing system. For example, you can:
- Convert a single-tier flood-and-drain system to a multi-tier flood-and-drain system.
- Convert a multi-tier constant-flood system into a multi-tier flood-and-drain system.
Rig Design Requirements
The final rig design should have:
- Multiple (more than one) vertical tiers.
- A cascading hydration design, where the overflow from one tier serves as the inflow for the tier below it. (The check valves aren’t useful if your design has each tier drain directly to the nutrient basin.) The bottom tier overflows to the nutrient basin.
- A pump that allows water to flow backwards through it (by gravity) when the pump is off.
The parts requirements are detailed later, but in brief, the only unusual part needed for each check valve is a lighter-than-water ⅝” ball. I acquired a bag of 100 (including shipping) for $24.
Step 1: Review an Actual Deployed System
The image above shows my system. It has four 3” PVC pipe for planters. The three check valves are located in the yellow boxes along the right. (We'll be making these.)
- In this "version 1.0" rig, I placed the plumbing through the end-caps of the PVC planters. I don’t recommend this approach, since the pipe connections are difficult to position, clean, and make water-tight. Version 2.0 will be configured like the schematics in the steps below, where the hard plumbing comes through the bottom of the planters.)
- My own Web site is http://cadtogadget.com, which contains various notes on hydroponics and other projects. Feel free to subscribe!!!
- I’d like to thank Bruce Gee, whose A-Frame rig at the 2016 Maker Faire inspired this whole effort. See his Web site at http://waterworks-hydro.com/, in particular the design and parts list shown on page http://waterworks-hydro.com/a-frame/. (Bruce’s A-Frame system as shown there is non-cascading, constant-flood type, so check valves deployment wouldn’t be needed for it.)
Step 2: Review Single-tier Flood-and-drain Mechanics
This step describes components and operation of a standard (single-tier) flood-and-drain (a.k.a ebb-and-flow) hydroponics rig.
Note: The relative merits of a flood-and-drain vs a constant-flood hydroponics rig are discussed on the Web. (We'll review these systems shortly.) I initially made a multi-tier constant-flood system, but the flood-and-drain system seemed more natural for the plants, and a bit more maintainable. For example, in the "drain" state, planters can be more easily removed for cleaning or general rig maintenance. The check valves allowed me to easily convert my system to a flood-and-drain rig.
The first image above shows the main parts of a flood-and-drain system:
- The nutrient basin contains the nutrient solution, which I’ll call “the water” in the remainder of this instructable.
- The planter (orange box) is a "floodable" water tight container of arbitrary shape. Plant pots, or baskets, are either set on the bottom of the planter, or (as shown above) suspended from the top.
- The “dam” (in purple) is any device that begins emptying the water when it gets to high. This is commonly a PVC pipe, with an open top that serves as a spillway, through which the water is returned to the basin through the overflow return hose. This feature controls the flood cycle (pump on).
- The pump is a type that can pump water at least to the height of the spillway. It must also allow water to drain back through it when it’s turned off. This last feature enables the drain cycle (pump off).
- The pump turns on (second image). Water begins filling the planter.
- The spillway breached (third image). When the water starts spilling over the dam, the system is in a recirculating state. The planter stays in this this state for as long as the pump is on, perhaps several minutes, enough to soak the plant roots and media.
- The pump turns off (fourth image). Gravity pulls the water back through the pump to the basin.
It goes almost without saying, but you normally want to connect the pump of a flood-and-drain system to a timer. I have might set to run for 8 minutes at a time, 5 times a day.
Step 3: Review Multi-tier Constant-flood Mechanics
This step reviews the components and operation of a multi-tier constant-flood hydroponics rig, where the plant roots are continually immersed in a recirculating nutrient solution.
To make this, we can simply extend the model of single-tier flood-and-drain system, described in the last step, by adding several vertical tiers (extra planters) between the existing planter and the basin, as shown in the first image above.
The second image shows the water movement when the pump is turned on. The overflow of each of the top three tiers becomes the inflow for the tier below it. The bottom tier drains to the basin.
Step 4: See Why Last Design Won't Work As a Flood-and-drain System
If we turn off the pump of our multi-tier constant-flood system, we can see the top tier start to drain, as shown in the first image above. However, when the top tier finishes draining, the lower tiers remain flooded. There is no mechanism to drain them.
Of course, we want all tiers to drain. In the next step we'll see how this can be corrected with the use of our check valves.
Step 5: The New Check-valve (system View)
The yellow boxes in the image above shows new plumbing in under the lower three tiers. Each area includes a drain line that leads to the common drain line, plus our check valve (shown in red).
As mentioned earlier, the check valve:
- Prevents water from flowing up, and...
- Allows water flow down. (The water flows down, if the top-side water pressure is greater than the bottom side water pressure.)
In the next couple of steps, we'll see how it works...
Step 6: Check Valve Mechanics -- Ball-down
The check valve comprises a lighter-than-water plastic ball that shifts between:
The perforated top end of a pipe, as shown above, where water is allowed to flow down, and ...
Step 7: Check Valve Mechanics -- Ball-up
... the smooth bottom end of an adapter, as shown above.
- The ball-down position occurs when water pressure above the ball is higher than the pressure below it. Water is allowed to flow down.
- This ball-up position occurs when water pressure below the ball is higher than the pressure above the ball. In this case the water is prevented from going up.
Lets see the check-valve system in action...
Step 8: System Action With Check Valve: Power On
We turn on the pump. First, the ball in the tier-one valve floats up, blocking water from entering the tier-one planter.
Step 9: System Action With Check Valve: Top Tier Filling
The check valves for tiers 2 and 3 engage next, and water is forced to the top tier planter.
Step 10: System Action With Check Valve: All Tiers Flooded
Soon all tiers are flooded. Note that the system now resembles the multi-tier constant-flood case described above.
In the flood stage, all valve balls are in the up position, since the pressure on the bottom pipes is greater than the pressure from the top pipes. No water flows through the valves, ensuring that all water flows to the tier below, through the local spillway.
Let's shut off the pump...
Step 11: System Action With Check Valve: Top Tier Drains
If we turn the pump off at this point, the top tier starts to drain through the main supply line to the basin (though the pump).
Step 12: System Action With Check Valve: Third Tier Drains
Now, when the water level in the main drain line goes below the level of the third-tier water, the ball in the third-tier check valve drops, and the third tier starts to drain.
Step 13: System Action With Check Valve: Last Tier Drains
The process continues until the bottom tier drains, and the drain cycle ends.
Step 14: Making a Check Valve: Collect Required Parts
The following are the most effective combination of check valve components I’ve found so far:
- A 1/2” PVC pipe (at least 1.5” long)
- A smooth lighter-than-water ⅝” ball
- A ½” slip to ½” threaded female adapter
- A ½” male threaded to ½” slip adapter
The pipe and adapters are readily available at major hardware stores. A floatable ⅝” ball (part #2 above) was harder to find. After much searching, I bought a batch of 100 balls for $12, plus another $12 for shipping, from US Plastics. (Please let me know if you can find a cheaper source.) Here’s a link information about their 5/8" polypropylene ball. I chose polypropylene because this material floats. Polyethlene also floats, as should some hollow balls. Find ones whose specs indicate a "specific gravity" of less than 1.
For part #4 (½” male threaded to ½” slip adapter, at far right in image above), take the time to shop for ones that have smooth, round openings to the threaded male end, free of manufacturing burrs. This will ensure a tighter fit when the ball is at the top position preventing water flow.
Step 15: Making a Check Valve: Find a "notching" Tool
The only tool required is one that will help you make the notches at the end of the PVC pipe (part #1). I used a Dremel tool with a rotary wood carving bit, as shown in the image above, but you can use a jigsaw to make triangular notches, or even a manual file.
Step 16: Make a Check Valve, Step 1: Add Notches to One End of the PVC Pipe
Secure the pipe in a vice or clamp, then cut three or four notches in one end of the PVC pipe (part #1). The above shows the result of using the Dremel tool.
Note that the notches don't have to be neat, just positioned so that ball rests nicely on the ridges between the them. Try to make the notches about as deep as shown.
Step 17: Make a Check Valve, Step 2: Assemble Pipe and Ball
Stand the PVC pipe on its smooth end, and place the PVC ball on the notched end.
Step 18: Make a Check Valve, Step 3: Add the Slip-to-female-thread Adapter
Press slip side of the ½” slip to ½” threaded female adapter (part #3) onto the pipe, such that the notches in the pipe are just covered. IMPORTANT: don’t press the adapter down as far as it will go, otherwise, there won’t be room for the ball to move.
Step 19: Make a Check Valve, Step 4: Add the Male-thread-to-slip Adapter
Screw the ½” male threaded to ½” slip adapter (part #4) onto the female threads of the first adapter until snug.
That's it! The check valve is made. Not much to it.
Step 20: Deploy the Check Valves
At this point, you deploy the step valves to your rig using appropriate adapters. The above image shows one of the adapters on my system.
Step 21: Final Notes
- Valve not watertight. When the check valves are blocking flow (the ball is at the top of the valve), it won’t be 100% water tight. You’ll likely be able to see a bit of water entering the lower tiers’ planters as higher tiers are being filled. This is OK. The idea is to keep the pump line pressure high enough so nearly all of the water makes it to the top tier.
- Optional: Glue parts #1 and #3. My experience is that components #1 and #3 fit snugly enough together, even though they’re not pressed together as far as they can go. (Remember, this is very low pressure here.) But if you find the connection is too loose for comfort, you can simply use standard PVC pipe glue to connect them. Take care not to allow the wet glue to contact the ball.)
- Ping pong balls. I considered using ping pong balls for the check valves, however, the required PVC components were much bulkier, and anyway I couldn’t readily find a combination of correctly-sized adapters that would work. It could be done I’m sure with the use of washers and further experiments. A ping pong system would actually be ideal if the planters were large.
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