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.

[Soniq420]

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]

Originally Posted by Soniq420

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