If you’re at all familiar with cannabis cultivation, you’ve probably seen an irrigation manifold before. Sometimes they’re called by brand names, other times they’re called by nicknames like “octopus heads” or “squid heads.” Those monikers are well-earned, as manifolds do look like octopi reaching their tentacles out to tend to your weed plants. They don’t only add that deep-sea element to your grow, though. Manifolds are a cost-effective way to centralize your irrigation and keep your garden tidy. As great as manifolds are, there are some situations where you would be better suited using a different system. So, when should you be using a manifold and when should you avoid them?
Before we get into that (don’t you just love hearing that?) it’s important that you know what a manifold does and how it works. Say you have 12 pots, and you want to run one dripper to each of them off a piece of drip tubing. To do so you’d need to punch 12 holes and use those to run your smaller tubing to your plants. Now imagine if you have 72 plants on a bench with only eight feet or tubing to service all of them. That’s a lot of holes and barbs for one piece of tubing!
A manifold essentially takes the place of the tubing: it gives you somewhere to plug the smaller pieces of tubing into. The variety we sell, 12-outlet manifolds made by DIG, come with pre-installed drippers as “full” manifolds or without any drippers as “empty” or “body only” manifolds.
A manifold offers a lot of benefits over a piece of drip tubing. For starters, it’s designed to be re-usable. Drip tubing is resilient, but after a while it succumbs to wear and tear. Holes get worn out, kinks refuse to come out, and mistakes cause cuts and holes where there shouldn’t be. If you consider our earlier example, punching 72 holes in close succession can cause issues. If the holes are too close, the drippers may not fit. Two holes accidentally punched too closely can also just turn into one big hole, resulting in leakage. The reusable nature of manifolds also means that they’re ideal for areas with changing plant counts, such as a room doing double duty and cycling through both veg and flower plants throughout the grow cycle.
Another big benefit of manifolds over tubing is flow capacity. While you can technically run manifolds off of drip tubing, they are most often fed with PVC. PVC has a much higher flow capacity than drip tubing. For example, standard ½” (.700) drip tubing has a flow capacity of 220 gph, while a piece of ½” PVC has a flow capacity of 840 gph. You can fit almost four times the water through PVC as you can through drip tubing, which means you can water a lot more plants before having to add another line. This is most noticeable when using high flow rate products such as spot spitters or 4 gphdrippers, and is amplified when dealing with large numbers of plants arrayed in long rows. Considering how difficult it is to get tubing into PVC without leaks, using manifolds is an easy way to expand your watering capacity.
Now that you have a good idea of what a manifold does and why the ones we sell are the best (did you think this wasn’t at least partially shameless self-promotion?), let’s get into when they are appropriate and when they aren’t.
The basic rule when it comes to manifolds is this: manifolds are best when irrigating high-density, individually potted plants. The inverse to this is, of course, that manifolds are worst when irrigating low-density plants in beds. This often means “don’t use manifolds outdoors,” and while that’s not always the case I promise I won’t tell anyone if you want to use that heuristic.
The natural question here is “why?” Why are manifolds great for high-density, individually potted plants?
The density issue mainly has to do with the length constraints small tubing has due to friction pressure loss. 12-outlet manifolds work with 1/8” tubing by default, which has a maximum run length of 10’. They can also use ¼” tubing with the help of a converter barb, giving them a reach of 30’. Either way, this isn’t remotely close to the 400’+ that larger tubing sizes offer. The 30’ reach offered by ¼” tubing may sound like it mitigates this problem, but you also need to consider efficiency. It can be hard to find an area where 12 plants are at most 30’ from the manifold when dealing with low-density areas like outdoor fields. This means using manifolds to water less than 12 plants at a time, which ends up costing more money than the alternatives.
But why are manifolds better with individually potted plants? Using manifolds for plants in beds or rows has the same downsides as using them to water low-density plants. Plants in beds or rows, even with a high density, tend to be best watered by “bulk” methods like sprayers or dripline. Each port of your manifold may be able to water 5 plants with a sprayer on the end, but you still run into the same issue of having to find 60 plants within a 30’ radius of your manifold.
Manifolds shine in high-density areas with individually potted plants (read: commercial indoor grow operations) because they can move far more water to a larger number of plants than the alternatives. Despite the high density, bulk watering of potted plants doesn’t work well, especially with plants like cannabis that don’t like water on the leaves, stems, or (Cheech forbid!) the buds. This means plants need to be watered individually, and 12-outlet manifolds are great at that. The standard layout is one port per plant, but in propagation areas with extremely small plants a 1/8” tee can be used to let each port water two plants. In larger pots that require multiple drip points for adequate root coverage, a tee can be used in the same fashion but with both drippers going into the same pot. The large amount of water needed for 3000+ plants in a small space can be carried more efficiently by PVC than drip tubing, leading to fewer zones and less money spent on valves, controllers, and redundant tubing.
Irrigation systems like these usually end up costing around $1 per plant. Yes, one single dollar per plant. Don’t you wish your lights cost that much?
All in all manifolds are an efficient and cost-effective option for grows of all sizes, assuming the circumstances are right. As with any tool, knowing when to use it and when not to is essential to using it effectively. Irrigation systems are no different. The process we’ve gone through to discuss when and when not to use 12-outlet manifolds in this article are not only applicable here, by the way. You can use the same parameters to evaluate other irrigation products. Consider their limitations and their strengths, compare them to other products, and consider what you’re trying to accomplish with them. Or you could just call us at 844-420-4100 or email at firstname.lastname@example.org and let me do it for you :)