Venturi Fertigation

[Beil]

Has anyone successfully made a venturi fertigation system with drippers?
I got a 3/4" venturi and set it up for my fruit trees (adding granular fertiliser and watering it in with drippers is a PITA). Was only after that I found out that back pressure (like that from drippers or even sprinklers) nulls the effect, so instead of sucking, the water goes out of the unit.
I've heard that I maybe should have gotten the 1/2" version, for it to work better.

I CAN get it to work with the flow turned right down, but the bottle of fertiliser has to be raised about 1.5m, which is fine as it works, just annoying getting the ladder out. I'll build a dedicated stand if I can't get it to work ground level. Don't really want to buy another unit and it not work anyway.
Tried adding a backflow preventer on the outflow, but that doesn't help .

 

[Madmick]

I don't know if it will help but on my misting kit out the back , after it gives a 30 sec mist , the timer cuts of the water supply

Rather than it just draining the rest of the water in system out of misters it has a relief value that opens when the water goes the other way and releases excess onto a few plants ,

That way there's no pressure in the pipes it stops at the timer until it re opens

 

[Aye Shroomer]

This is why I like passive watering like sips. Simply fill and forget

 

[Beil]

I don't know if it will help but on my misting kit out the back , after it gives a 30 sec mist , the timer cuts of the water supply

Rather than it just draining the rest of the water in system out of misters it has a relief value that opens when the water goes the other way and releases excess onto a few plants ,

That way there's no pressure in the pipes it stops at the timer until it re opens

Kind of applicable, if I don't block the end of the drippers it pulls the fertiliser at full flow, as there's no back pressure.
I wonder of some kind of release valve at the end would help, so it's not just open but it can vent, along with the back flow preventer

 

[Beil]

This is why I like passive watering like sips. Simply fill and forget

Is this them?
That'd be OK for small veggies, but the trees I'd like to fertiliser along the root spread (albeit the drippers just run both sides of the trees, so about 1/2 the roots by the time the warer spreads underground.

My technique ATM is to add the fert at low flow and when it's drained, turn off the venturi and turn up flow to water it in and run as normal.
Only about 5 minutes of actual work, just the effort of getting the ladders out.

I'm planning on extending the drippers out the front to the roses running off the same line, so I should be able to reduce back pressure there with 40m of poly and another 12m of drippers, but that's down the track with life.

 

[The Happy Camper]

Could it be that the venturi needs more pressure so as not to need the ladder?

The start of your video shows you turning on the splitter at your mains tap a tiny bit. What happens whith the splitter fully open?
Might need a regulator somewhere in there.

I like little projects like this.
Gets you outside, doing and learning.

More questions than answers. Haha.


Good stuff.

 

[Beil]

Could it be that the venturi needs more pressure so as not to need the ladder?

The start of your video shows you turning on the splitter at your mains tap a tiny bit. What happens whith the splitter fully open?
Might need a regulator somewhere in there.

I like little projects like this.
Gets you outside, doing and learning.

More questions than answers. Haha.


Good stuff.

Nah, when there's more pressure it pushes water out the venturi regardless of the height.
There's a 100kpa pressure reducer at the tap, my mains is 550kpa. So even though it's reducing the pressure, the flow is is high, so theres more back pressure when it cant get out of the dripper, hence just opening the tap slightly so the flow is low aswell (I think, not 100% on the theory of it)


Aye, I like building stuff and figuring out how to do it, especially on the cheap. Pisses my wife off when I get deep into researching something and can spend weeks just reading up on stuff though lol

 

[Pikey]

Are you sure the pressure reducer is working correctly? I know @Rocket had an issue with some and found them to be unreliable

LINK : https://www.theserratededge.com/forum/threads/next-grow.1060/post-91056

 

[Beil]

Are you sure the pressure reducer is working correctly? I know @Rocket had an issue with some and found them to be unreliable

LINK : https://www.theserratededge.com/forum/threads/next-grow.1060/post-91056

I'll have to borrow BIL pressure tester to check. Worth checking it like.

 

[Aye Shroomer]

Nice mate.

I’m using 40L greensmart planters

I’m in a rental though so I’m hesitant to put down large garden beds. I have one now but it will be a pain if we move. Not that we have to move but if.
Also want to make an Ibc wicking bed.

If I had my own place i would certainly set up something bigger and more permanent

 

[Beil]

So behind this (see photo) , there is supposed to be a spring ball gasket, the one I set up didn't have it. Only found out coz I decided to buy a 1/2" instead of a 3/4" to test out if the sizes made a difference (I doubt it will as the bore is the same size :/ ). But when I opened it I noticed a little ball behind the rubber washer. Looked at the one I had set up, not there. So put it in and it worked a treat, with the Venturi and bucket on the ground, not raised 1.5m!
Used my second pressure reducer (as the micros on the same line didn't work with the first one) and when the Venturi isn't in operation the micro sprays still work (which isn't an issue as I don't mind doing the shade/hanging basket with liquid by watering can, and I can just put pelletised in the pots and the most will get it down).
There's a video of it working but too large to upload

Chuffed

 

[benn0]

Sorry to bump an old post but I'm currently exploring venturi for my irrigated garden this year, does the venturi and valves and what not have to be above the pot/bucket of nutes?
Also did you end up getting it working well with drippers? I'm worried there wont be enough flow through my drippers to pull solution from the fert tank/bucket/pot

 

[Beil]

Sorry to bump an old post but I'm currently exploring venturi for my irrigated garden this year, does the venturi and valves and what not have to be above the pot/bucket of nutes?
Also did you end up getting it working well with drippers? I'm worried there wont be enough flow through my drippers to pull solution from the fert tank/bucket/pot

I got it working, the missing ball bearing in my last post was the issue. My Venturi is set up on a start dropper with the bucket on the ground. Roughly 40-50m of drip line, plus about 20m of black poly to connect it from the back yard trees to the front years roses. Along that route is a side section for my hanging baskets with micro sprays that is rigged with a valve to turn them off (this section is the key as it turns out...)

The only issue with drip lines is that the very nature of the drippers causes back pressure, there's no free exit for the water as it's forced out the holes. So there isn't enough of a drop in pressure after the Venturi to cause suction.. due to the... Back pressure the drippers cause.

My accidental solution was that when the hanging basket section was opened and there was more of an open pathway for the water to escape through the micro sprays, it reduced the back pressure enough and it sucks the nites up straight away... If I close the micro sprays off and it's just the drippers... No suction.
The micros don't put out a proper spray when the Venturi is open though, but the Venturi works so that's the main thing.

So, if you're going to do it, you could just add 6 micro sprays (the number I have in my hanging basket section) either plugged right in the drip line, or route off a section to an area where micro sprays will be ok and have them working the whole time.... This is what I'll eventually be doing as the hanging basket section will be getting removed in a year or so.

Also, just buy the Venturi with the 1/2" thread, getting the 3/4" one like I did, just makes making the rig more of a pita and from what I read it doesn't make a difference on a domestic scale, especially as you'll be using either 13-19mm poly (or hose) to connect to mains and then it'll be going I to 13mm drip line.....


Also, make the rig out of PVC fittings and glue, not poly like I did, it's so tight to tighten them it's annoying and mine does have small leaks, even with clamps... Make it with PVC and glue, it'll be more rigid and less prone to leak.
I did poly as it was cheaper ($30 in fittings plus the Venturi) as a proof of concept, but haven't got round to making the final solid PVC one

I also don't use a pressure reducer, it comes straight from the mains tap to the Venturi. No issue as far as I can tell with the drippers.
Didn't make a difference to the Venturi working or not with the micros on/off with a pressure reducer either.


I think that's everything I learnt from this lol.

 

[benn0]

I got it working, the missing ball bearing in my last post was the issue. My Venturi is set up on a start dropper with the bucket on the ground. Roughly 40-50m of drip line, plus about 20m of black poly to connect it from the back yard trees to the front years roses. Along that route is a side section for my hanging baskets with micro sprays that is rigged with a valve to turn them off (this section is the key as it turns out...)

The only issue with drip lines is that the very nature of the drippers causes back pressure, there's no free exit for the water as it's forced out the holes. So there isn't enough of a drop in pressure after the Venturi to cause suction.. due to the... Back pressure the drippers cause.

My accidental solution was that when the hanging basket section was opened and there was more of an open pathway for the water to escape through the micro sprays, it reduced the back pressure enough and it sucks the nites up straight away... If I close the micro sprays off and it's just the drippers... No suction.
The micros don't put out a proper spray when the Venturi is open though, but the Venturi works so that's the main thing.

So, if you're going to do it, you could just add 6 micro sprays (the number I have in my hanging basket section) either plugged right in the drip line, or route off a section to an area where micro sprays will be ok and have them working the whole time.... This is what I'll eventually be doing as the hanging basket section will be getting removed in a year or so.

Also, just buy the Venturi with the 1/2" thread, getting the 3/4" one like I did, just makes making the rig more of a pita and from what I read it doesn't make a difference on a domestic scale, especially as you'll be using either 13-19mm poly (or hose) to connect to mains and then it'll be going I to 13mm drip line.....


Also, make the rig out of PVC fittings and glue, not poly like I did, it's so tight to tighten them it's annoying and mine does have small leaks, even with clamps... Make it with PVC and glue, it'll be more rigid and less prone to leak.
I did poly as it was cheaper ($30 in fittings plus the Venturi) as a proof of concept, but haven't got round to making the final solid PVC one

I also don't use a pressure reducer, it comes straight from the mains tap to the Venturi. No issue as far as I can tell with the drippers.
Didn't make a difference to the Venturi working or not with the micros on/off with a pressure reducer either.


I think that's everything I learnt from this lol.

Absolute legend mate, great write up, this helps so much, thank you!
Was a bit worried about the back pressure of having just drippers and ill be sure to grow some friendly flowers somewhere under sprays!

 

[Beil]

Absolute legend mate, great write up, this helps so much, thank you!
Was a bit worried about the back pressure of having just drippers and ill be sure to grow some friendly flowers somewhere under sprays!

No worries. It was something I wanted to rig up for ages so spent a lot of time trying to suss out what issues I had and how to over come them once I made it... Just don't lose that ball bearing if you open the suction bit!