Making a Venturi

[Stealthy1]

Ive made a few of these for my ponds a while back and they worked good so I figured I try to design one to work with my existing setup youll notice in my Hydro prototype I had a valve at the end of the line for this purpose.

First Ill go through the pros and cons of a venturi

Pros:
The bubbles are much smaller and the turbulence created helps dissolve the O2 better.
You recirculating the Rez water wich helps keep the O2 in it as opposed to a bubbler that the bubbles just rise to the surface.

Cons:
A poor venturi can reduce the flow by about 2/3rds
some are very noisy (not mine for some reason)

Ok so I used random spare parts I had around to design and build this one.
Ive never built one this small before and I am limitted by matterials but basically you want something like this

As you saw in my hydro setup im using 1/2" pvc so ill use that and I have some hard plastic spacers from lord knows what project and they fit right in, Bonus.
You can see here but theres a hole in the center of black spacer

Then I have to taper the inlet and outlet I used 2 of these spacers to give me the length I want.
Ideally the taper should be more gradual but I am limited but my dremel bits. (bad pic sorry)

I do this to both ends and insert so the outlet has more pipe after it. (not really enough here but I'm to lazy to cut another piece)

Notice Ive drilled a hole for the air line I got a little overzealous with the drill and made it a bit to big.
Here it is all together.

stupid me no pictures of it in action...
But its works good only thing is its too big....yes too big
usually with venturis it restricts the flow and this is a problem, but here there is not enough restriction. it simply lets to much water out so I will run it using another smaller pump as I dont feel like redesigning it when I have so many pumps around lol.

 

[tgadfgadgf]

So when are you going to get this bad boy up and running in the "grow journal" section?

 

[Stealthy1]

Might be a little while yet, have to wait till the contractors leave then build the cabinet when my tenant is not home.
So yah if the stars are aligned just right then maybe within a month but no date is set.

But I do have seeds germinating for an out door grow now. damn things are taking forever though.

 

[Keith Lake]

So only the motion of the water rushing by is adequate for drawing in the air - or you have to put a little positive air pressure on the inlet?

 

[PitViper]

I think your on to something very cool....but not for nothin.....I use 2 260 per hr powerheads and air stone.....43 bucks. ....my res bubbles like witchs cauldron

 

[Stealthy1]

So only the motion of the water rushing by is adequate for drawing in the air - or you have to put a little positive air pressure on the inlet?

Right same idea if you have a garden hose running and you pinch the hose in one place it will usually keep a somewhat pinched shape when you release it.
When you pinch it, It creates a restriction the water running through this restricted area has to speed up which creates a vacuum.

This is the principle the trick is tuning the restriction to get enough vacuum to overcome the water pressure while not reducing the flow to a trickle

You can apply an air pump to it if you like but you want just enough to overcome the pressure from the water in the rez. and let the venturi suck it in if you just put a pump on it will work but the air bubbles will be big and just float to the surface (like a bubbler) The venturi effect creates a fine mist of bubbles that stay in the water because of there small size and are more likely dissolve in the water.

This is more useful for ponds and fish tanks than hydro setups though and if you have a air pump why not just put an airstone in there and be done with it.
They're not that common in hydro systems because of their quirks and the inadequate size of most hydro pumps

In retrospect this was more my inability to do what others do than a solution thats practical for everyone...lol

 

[Stealthy1]

Thanks Shadow for bringing this back from the dead...
Ive finally got this thing in action!
Check it out in my journal

 

[Stealthy1]

Weird how members dissapear along with all there posts...

Anyways I used the venturi on a 400gph pump 15min on/15min off and my root structures improved immensely over just having air stones. and the airstones eventually clog up the venturi works every time you turn the pump on.
I had a huge healthy root ball the likes of which Ive never had on any of my plants.

Next time I do DWC I will use only venturis with the pump out of the solution to keep it from getting the rez too warm.

 

[Kotton Mouthe]

Stealth, great idea using a Venturi style setup on the hydro system! I never thought of that. Have venturi systems on my saltwater tanks. It now make perfect sence to me. What strains are u planning on growing in this bad boy? I will be keeping my eyes on this one. Count me in for the long ride. Goodluck

 

[OutdoorHydro]

For me venturi pumps are superior to airstones. I'm not sure exactly what it is, but there's something magical about keeping the nutrient circulating at that speed, plus more oxygen is always better. The size of the bubbles and the fact it keeps everything flowing is probably what makes it work so well. With airstones, you break the surface tension of the water a bit but there isn't enough agitation the way most people have them set up. I kind of overdo it with oxygen anyways, I'll put like 3 airstones in one 10 gallon DWC and hook up a pump made for 4 and think it's not enough.

I've had great results with venturi pumps so far. Maybe you guys can help clear up a debate I am having in another thread about venturi vs. Airstones:90F Rez Temps No Problem