Homemade Irrigation

Most important thing is the head difference between the 4000 L tank and the tubes with the holes.

If you want to make a mechanical system, you will need to work with equations where pressure, speed, and height are involved, such as the Bernoulli equation.

However, that open loop system would have poor performance as any of the parameters changes.

If you want to have a solution that will actually work, get an electromagnetic valve for each of the 80l tanks (small valves for small flow rates), attach some sensors to every tank to measure height or pressure (which defines the output flow) and use a controller for the system.

I would not be suprised if your idea was already implemented as a DIY project with a Raspberry Pi credit card size computer.

And as always, if you lack the experience and you can afford it, call a professional technician to do it for you.

Feed each tube from the middle, not an end.

Start small with the holes and enlarge as needed.

Same with the number of holes. It's always easier to drill more, larger holes than plug them if too big or too many.

You'll know when you've got it right on one tube then just duplicate the rest.

Forget about any fancy formulas and just wing it.

You have some good reply's so far.

I don't know how much investigating you've done so far,... have you considered a soaker hose?

Well in my opinion to do it right you'll need a feedback mechanism to measure the moisture level in your growing tanks...are you using a growing medium? or just spraying the roots....there are different methods hydroponics, so the first step is to identify the system type you want to use....then you can flesh out the supporting infrastructure...in any case the amount of water needed will vary over time, the feedback system should have some sort of alarm in case of system failure....and the water supply system should be controllable over a range of demand....You should also have a nutrient monitoring system or scheduled methodology of feedback testing...these demands may also vary....

...or you can just go with a complete kit...

...there's loads of videos online....

At some time you may want to incorporate fish into your system making it aquaponic ....

https://en.wikipedia.org/wiki/Recirculating_aquaculture_system

Couldn't you use a valve to adjust the flow rate?

Not knowing the design of the tank, that may change the head pressure and the tank drains, and change the velocity and pressure as it drains. But it would be a simple answer if the change is negligible.

• This installation is designed to be running unattended for a little under 4 weeks, according to those figures.
• 1.6cm³ per second onto what area? The larger the area the smaller the holes.
• What is the hydraulic head to be applied to the distribution outlets? The higher the head, the smaller the holes.
• How many holes are envisaged?
• If the plants were outdoors then the installation wouldn't be necessary, as it would likely rain in that time in most locations and only top-up watering would be necessary to achieve the volume criterion.

There are plenty of adjustable drip irrigation valves around.

A couple to consider.

Manifold type

Simple and cheap type to plug into poly pipe Put in more than you think and then throttle back until you get the flow rate you want or add more as needed. A cheap inline filter with these will prevent blockages.

Obviously flow rate will vary with head height as water is consumed or replaced, so expect a bit of irregularity or fit a pressure pump.

A liter is about 20,000 drops of water, so one liter per hour is a little less than 6 drips per second.

Why am I bringing this up? Because it isn't easy to drill holes specifically for drips per second. All kinds of factors that are negligible at higher flow rates start to come into play in the drips per second range and below.

Luckily as noted by other commenters there are cheap readily available solutions to be had. Flow regulators for drip irrigation come in standard flow rates in the ranges you are considering. Some are even pressure compensated (to some degree).

No need to reinvent the wheel. Use the expedient cheap resources available.

I'm curious, you a say a " few " tanks, how much is a few. If you use a 4000 liter tank and feed that into 3 tanks, with a flow rate of 6 liters per hour, is this to be at a site where the tank will only be refilled once every 9 days ?

What exactly will you be " growing " , that you need such an extended supply of water ?

If you are trying to grow plants, then you really need intermittent wetting of the roots rather than constant flow. The roots need to be exposed to air or else they will rot.

You might like to look up "flood and drain" systems or "nutrient film technology" systems for two different options. F&D re-uses the nutrient solution while NFT uses such a slow flow that all nutrient is removed by the plants and the outlet water is run to waste.

Your four week expectation is adventurous, as both F&D and NFT usually have a clean water flush once per fortnight to remove accumulated salts in the growing media.

There are many good studies/advice on how much water per plant per day and you need to adjust for plant growth with NFT, while F&D is far more forgiving.

If you are prepared for the risk of cross contamination, F&D with four beds with the nutrient moved in round robin is almost the right ratio for timing.

Good luck.

I hope you've remembered to allow for the weight of the full tank. You'll need a pretty substantial structure (or a handy bit of high ground) to support it!

Putting it All Together
There is a bunch of wisdom scattered through the various posts. Here is my take on which ones really matter to assemble into a coherent working plan rather than a setting up a disaster:

1. From Just an Engineer #12. "If you are trying to grow plants, then you really need intermittent wetting of the roots rather than constant flow. The roots need to be exposed to air or else they will rot."
For most plants this is a near certainty and will, if ignored, lead to a catastrophic collapse of the operation. A second attempt will collapse even faster since the flora and fauna causing collapse is nearly impossible to clean out of a site. Nature
loves diversity, not stasis.

2. From SolarEagle #5 post:
"incorporate fish into your system making it aquaponic ...."
Nature is flora and fauna. They originally evolved together and the beauty/complexity of that relationship is the subject of literature/poetry. Attempting to glibly reproduce the chemistry of that relationship is beyond modern technology. Even the most expert human is just a pathetic rerun of "The Sorcerer's Apprentice" when it comes to keeping a balance over the long haul. There is at least a chance if the human enlists a few fish in the effort. The smaller the operation, the faster the balance can evaporate.

3. From Ivanov327950 #2 post:
" implemented as a DIY project with a Raspberry Pi credit card size computer." This little yeoman can keep detailed records of "what happened when", an essential element of long term farmer success. You can write your own scripts for what to do next time and it will dutifully carry out your marching orders, on time every time. You can add sensors and actuators over time to sense and react to any situation.
The Pi runs Linux(raspian is a dialect) which is hands-down the most capable, ubiquitous, and flexible(open source and free) system there is on the planet. It probably runs your TV, refrigerator, and cellphone and as the poster comments there is likely an app for your project.

4. From Just an Engineer #12:
"There are many good studies/advice on how much water per plant per day and you need to adjust for plant growth with NFT, while F&D is far more forgiving."

F&D is far more forgiving especially, if F&D implements an aquaponic system.
Fish activity is a canary in a mine for your plants. Healthy, active fish will become lethargic and show signs of stress well before your plants decline. Fix the problem and your fish will likely recover but fix the problem after you notice plant decline
and the plants probably will not recover.

5. Fresh material:
The pi is great at keeping temperature records, do it, and log your observations regarding the activity/appearance of your fish with the time. The pi can run a big, beautiful, used(cheap) HDMI monitor. There are native editors(gedit,vi,..) which you should use to keep all your notes and when you made them. It can control your irrigation rates if you build/buy a pi interface to do it. Now you are fully flexible with your flow rates and not locked in because you drilled a certain number of a certain size hole. You could control salvage washing machine solenoids for a cheap, fully flexible DIY irrigation system with an OTS relay driver card. Use the pi to change things up and watch carefully the results. Make your setup a big science lab. Repeat your experiments to see if they are reliably repeatable. Learn from your farming and become a recognized expert. Eat a fish with fresh veggies once in a while. BTW, city water is full of poisons(fluoride and chloramines) so you should add water from highly filtered vending machines or distilled when you need more water. Avoid "natural" water sources as well to keep poisons, parasites, and pathogens
out of your closed system. Have fun !

thewildΩtter

Your response (and other's) reminds me of the saying "ask an engineer what time it is and they will tell you how to build a watch." And a digital watch at that.

"What would be the best way for me to calculate the right number and size of holes needed for a specific flow rate. I want the flow rate very slow, at around 6L/h," has morphed into a complex, not so cheap, hodge podge of "here's the way I'd do it" instead of helping the OP figure our the size and number of holes to drill in his tubes.

Yep, you are right again. Start small and few, and add/increase only as needed.

Anyone should be surprised how fast 6L/hr shows up, with not much over a drip tock of the clock.

That'll teach him not to bring that kind of stuff here... because before you know it... we'd solve it for him...

and here it is.

Now THAT is an irrigation system. Sorry for shouting, but I just had to.

Wow, that useless gadget thread got shut down, didn't it?

My question: Why is so much water going over the spillway of this dam? Is it flood season? Why isn't that water (head) being used for electric generation?

Why aren't the fish jumping and cavorting on the water?

...we're homeward bound from the Arctic Round, rollin' down to old Maui.

Why is so much water going over the spillway of this dam?

Flow regulator broke...

Is it flood season?

Maybe its only half time at the football game.

Why isn't that water (head) being used for electric generation?

Jim: "Fred, didn't you install the generators?"

Fred: "?"

ROFLMAO!!! Nicely done!

Geepers, Lyn, you had already done that in post #3 by saying "wing it", which, by the way, for the stated request was exactly the right answer and would have worked even on twitter without straining the medium. Why did you say any more ? Maybe you too have at least the soul of an engineer.

Now, did you say you wanted to know how to build a digital watch...?

thewildΩtter

No offense meant but the forum members, myself included, seem to have a tendency to go off on the "that's not the way I'd do it" tangent too often. All well meaning, I'm sure.

From 1969 through 2000 I held titles with at least the word "engineer" in them. But, all through the years I've subscribed to the KISS principal. That came from growing up in a poor farm family in central Arkansas where we didn't know any other way.

"Have gun, will travel"

You sure that wasn't "have gum will travel"? At least we had choppers back then to chew our food (and gum) with back then. Now having to gum that gum by gum is not fair dinkum.

Some good points brought out by Lyn and Solar Eagle below.

You should go read about the design of the gardens at the Taj Mahal. The engineers on this project solved it elegantly to have the same fountain height at each nozzle. You can also do this in a similar way as they did.

Obvious answer: same (low) dynamic head at each nozzle opening. I will not give the secret away other than to say that.

"Some good points brought out by Lyn ans Solar Eagle below."

...

I am uncertain if you are seeing into the future or just have your screen upside down.

That is probably not all that is upside down in my world right now. My associate blew up our experiment last weekend, and I am still waiting on him to report the details, and data files back to me as to root cause. (I already know he forgot to enable the water pump that refills the reactor, so once again it is lack of coolant/reactant, leading to rapid overheating at the last.

Pressure ballast volumes and the fountains of the Taj Mahal

This is all you need to know:

(1) the supply to the pots below each fountain were larger than required so pressure was constant inside each pot

(2) the nozzles were all then the same identical nozzle, so it follows that the sprays were uniform.

very simple, very elegant solution to an age old problem.