5 Drip Irrigation Mistakes to Avoid 

Glad you're enjoying your drip system! I got semi-addicted after my first one and kept finding excuses for more beds lol. If I'm understanding correctly, I believe you'll be good to go as far as length goes, as you do have the right of it, the 200' limit is for a single run. Make sure to account for the flow rate as well, 1/2" tubing is good for up to about 200 GPH, after that the friction loss curve can get pretty steep, particularly on long'ish runs. To calculate the flow rate of the system, just add up all the emitters you have operating on it -- for example, 300 0.5 GPH emitters (whether button drippers or in drip line) will have a system flow rate of 150 GPH. Include any you'd like to add to the system to get the proposed flow rate. If it goes over 200 GPH (or gets really close) it may be worth zoning the system -- fortunately for hose bib systems, zoning is pretty straight forward. You can use one of those faucet Y's to easily create a second zone, or a two-outlet timer if you're automating the system :) You're welcome to reply here with any follow-up questions!

How long are each of those separate runs going to be to get to the in ground bed and separate raised beds? The reason I ask is the main thing to consider where you're at in the process now is the size of line to use from each split -- the primary consideration in sizing a mainline is friction loss. Friction loss (pressure lost from friction) is a mechanism of the material of the line, diameter of the line, the length of the line and the flow going through it. Unless the distance is far (greater than 200') you'll likely be able to use 1/2" tubing here. 1/2" tubing is generally good for up to 200 GPH in flow and 200' length -- I can't imagine the raised beds or in ground beds getting anywhere near 200 GPH, so line length is going to be the primary determiner of what size line to use there. That's a bit of a long way of saying it's highly likely you'll be able to use 1/2" :) If any questions come up while you work out your system, don't hesitate to reach out!

Good question without a completely clear answer, but I'm going to tentatively say yes due to my understanding of the physics of such a method from larger systems. The physics suggest that when you have it connected to the mainline on both ends like this, you've essentially split it into two smaller portions. Though in practice it's unlikely to be a perfectly even split (meaning I wouldn't exceed the maximum by too much), it should provide enough flow from both sides to essentially be two separate runs. This of course assumes other factors are accounted for, such as the mainline being within acceptable limitations in regards to length and flow, and sufficient pressure and flow from the source to begin with. Basically, if you're not overtaxing the source or suffering too much friction loss in the main, it should be able to feed ample pressure and flow into the 1/4" line from both locations where it connects. Very good question, normally I recommend to avoid loops or similar on smaller systems since there is typically not much benefit, but when exceeding a maximum recommended length there can be some benefit as described here. Thanks for the great question!

@@dripdepot thank you I guess I’ll have to try in the spring. I can always shorten the length of the 1/4” drip line if the middle emitters don’t work

@@tobruz You bet -- do you know about how much total flow in emitters you'll have in that line? If the flow demand (the sum of all the emitters there) isn't too high, I think the odds of success go up pretty significantly as well -- between low flow and being connected to the main on both sides, I think you'll be looking pretty good :)

@@dripdepot I am super impressed with the quick response time and detail answers to my inquiries- BRAVO!

There are actually two separate things, though sometimes they are referred to by the same names. Drip line comes with predetermined spacings -- there are multiple spacing options available, however, typically 6", 9" 12", 18" or 24" (depending on if 1/4" or 1/2" drip line is used). Poly Tubing is just blank tubing, often used as a water carrier to feed other emitters or drip lines. Emitters can be punched directly into poly tubing, however, and in that case the spacing can be whatever is desired. That's for 1/2" or larger tubing, for 1/4" tubing inline emitters can be used to provide any spacing desired. There's also a third item called Drip Tape that is very similar to drip line -- it also has predetermined spacings, but there are a lot more spacing options and emitter flow rates available, even up to 60" spacing. In 1/2" drip line, additional emitters can be punched in, just like you can with Poly Tubing (1/2" drip line is essentially 1/2" poly tubing with integrated emitters). 1/4" drip line and drip tape cannot have additional emitters added to them.

The size of drip line to use would be more dependent on how long your rows how -- if they're shorter than 30', 1/4" drip line can be used -- if they're longer than 30', you'll want to look at 1/2" drip line or 5/8" drip tape :)

Ok thank you! One more simple question, when choosing between a 10 PSI & 25 PSI Pressure Regulator, what am I looking for to make sure I choose the right one?@@dripdepot

@@911ThaSwitch You bet! Which regulator PSI to use comes down to which emitter you use -- if you'll be using drip tape, 10 to 15 PSI is the best bet (with 15 PSI for 15 Mil thick tape) -- if you go with 1/4" drip line, button drippers or 1/2" Poly Drip line, 25 PSI will be the optimal operating pressure. Most drip irrigation operates best right around 25 PSI, with the big exception being drip tape at 10 to 15 PSI :) If you have a mixed system, regulate down to the lowest PSI emitter -- for example, if you had both 5/8" drip tape and 1/4" dripline, run at around 15 PSI for the drip tape, as most 25 PSI emitters will still work great at 15 PSI.

Very good question here -- and you do have the right of it, the recommended maximum is largely due to friction loss (velocity also comes into play in wanting to keep water velocity at less than 5' per second). Your proposed solution, if I'm understanding correctly (let me know if I'm not!), sounds about like how we'd do it -- using a tee or similar to create more lines where each one is less than 200' rather than longer lines of 200' +. If it's not too inconvenient, your plan is definitely sound -- if it would be a pain to design/install it that way, how long over 200' would your runs be? The reason I ask is that the manufacturer of that drip line does allow for it to go over 200' in length with the 18" spaced drip line (by a good bit, even), so you may have some design flexibility here. And the 600 GPH at the spigot versus the 480 GPH in flow demand looks good -- always good to have a cushion between flow provided and flow demand as you have here. If you'll be running it all as one zone you'll likely need 3/4" mainline (possibly 1" depending on how long it is) to keep friction loss to a minimum, but the healthy flow will serve the system well :)

I think you understood my proposed layout. Basically I want to run 1” main line like 200-250’ to each valve. Then from the valve I’ill run a line down the hill with 12, 100’ drip lines branching off of it. So no brown 1/2”, built in emitter 18” apart, would have a run over 200’ (as each bracket or Tee, is only 100’). Water rate would be 1200 feet of tubing/1.5’ between emitters *.6 g/hr or 480 g/hr (and my spigot flow is 600 g/hr at 60psi static). You said above my flow demand looked good, but maybe I didn’t say enough. BUT, BUT when I spoke to rainbird, they said the drip lines can’t do more than 220 g/hr. Is that true? So I I have 12 Tee’s, each having a 100’ branch, so 12 100 foot runs, I can’t over 220 g/hr so my idea won’t work? Also how do I know what the velocity is? By putting so much tubing am I increasing the velocity? Thanks.

​@@wstt4 I suspect what RainBird meant was the same general rule we have in our literature -- ours says not to put more than 200 GPH through 1/2" tubing or drip line, sounds like they went with 220 GPH -- this means you'll still be ok, as it is similar to the general rule regarding the 200' length (it's all about friction loss and velocity) and it only applies to a single length of tubing or drip line. This means your 100' lengths should only have 40 GPH going through them (100', 18" spacing, 0.6 GPH emitters, double check my math though), well below the 220 GPH recommended maximum flow rate. and 200' recommended maximum length. In regards to velocity, if you're under the recommended maximum flow rate (for a single run) you'll be under the 5 ft per second -- meaning each of your 100' lines will be well under 5 ft per second in regards to water velocity :) Great questions and great planning you're doing!

@@dripdepotthanks for the amazing help. Final questions here. If I run 1” main line 200-250’ to each valve and then run from the valve, a 50’ line down the hill where the 1/2 tubing branches off 100’ from this 50’ line’, 12 times, so twelve 100’ drip lines off it, I assume that line down the hill can’t be 1/2 poly line bc then too much flow is needed to feed the twelve 100’ drip lines, like 450+ gallons, which is too much for a 1/2” 50’ tubing down the hill. Would I just use 1” pvc tubing for the 50’ tubing down the hill and connect the 12 drip lines to that 1” PVC tube? I was running a 1” pvc tube is needed to keep the water flow up. Can PVC tube be above ground? Also, Where would I put a pressure limiter and how much should I reduce the pressure to? Thanks so much. You guys are excellent.

Or rain bird QF Dripline Header 1” tubing looks like what I need. Assuming it is reliable long term, which I can’t seem to find solid reviews of it. And I also cant find maximum flow rates and PSI for it.