Mazzei injector position vs back pressure

[tefsom85]

I understand that venturi injectors require a pressure differential inlet to outlet but don't quite understand how that should affect my installation position. For example, I have a Mazzei injector (384X) that I am going to be driving with an Eheim 2028. I believe if I place the injector close to the Eheim I will have more pressure on the outlet side of the venturi than if I put it up nearer to the the top of the tank. For those of you that have used venturis for CO2 injection, where have you placed your venturis?

I have seen pics of IUnknown 's venturi where it was right at the canister but in a recent thread he mentioned that getting the pressure difference inlet to outlet had caused him to place it nearer to the tank outlet (guessing this means higher up closer to top of tank).

Also, it seems the pump driving the venturi is a big variable in all of this since the stronger the pump, the more pressure on the inlet side. Is this more of a trial and error process or is there a BKM (best known method) established?

 

[Tom Barr]

Generally more flow is better, Ehiems are not that good for flow unless it's the new super one or the older 2250/2260's.

If you want more CO2 mist in the tank, place the venturi close as you can to the return outlet. Less distance and travel time in the gas phase.

If the tank is very large and you want a lot of dissolved CO2 quickly, then placing the venturi inside the sump with it's own dedicated powerhead(however large you need) and feeding the outflow to the return pump's suction side.

That (rather than pressure drop differences due to placement along the line) is more the issue.

Regards,
Tom Barr

 

[tefsom85]

OK.. I guess I misunderstood your comment in a previous post. For my 120G, I am going to have a Eheim 2028 and a 2250 for flow. I had thought you said that I would be wasting the flow potential of the 2250 if I put the venturi on it. What you are saying here is to put the venturi on the return of the 2250 close to the outlet?

I'm not trying to be dense but want to make sure I do the right setup for my tank. I do appreciate the help!!

 

[Tom Barr]

No, the 2028 ought to be enough flow for this tank.
Try and see, then try the 2250 as well.
Then see what you think.
There's no clear cut answer here.


Regards,
Tom Barr

 

[tefsom85]

OK.. got the 2250 delivered yesterday. Hooked it up and it definitely has alot of flow. That is, until I put the venturi inline with it. With the venturi installed, the flow slows to a trickle - but did put out mist. One thing I am concerned with is the fact that I got the 384x vs the 584. I'm gonna contact Mazzei and see if this is an inappropriate venturi for the 2250 (which btw is pretty much just an Eheim 1250 pump on a 5 gallon bucket - albeit a nice 5 gallon bucket ) Has anyone here used a Mazzei venturi on a 2250?

 

[Tom Barr]

Did you try a smaller pump with the mazzii?

The Ehiem giant filters are nice and worth it.
You can use all sorts of media.

Regards,
Tom Barr

 

[tefsom85]

Haven't tried a smaller pump. I was assuming, maybe incorrectly, that a smaller pump would have even more restrictions. I'll give that a shot as well. I know some people use Mag drives - maybe I'll try that. I have a note out to Mazzei to see if they suggest a different venturi when using the 2250.

WRT the 2250. It is a very nice filter with lots of room for media - only downsides are the thumbscrews and lack of disconnects. I'll add quick disconnects so that's no issue and I'm thinking about a tool for the thumbscrews so that shouldn't be an issue either. I'm happy you suggested this filter.

Also, for those interested, I found pump curves at ProCooling.com

Update: I got a response from Mazzei. Basically the response was that the 2250 did not have enough flow/pressure to drive any of their venturis. While I agree that it doesn't meet their specs, I would think that I can get the pump to work with a venturi as I was able to produce mist, albeit at a low flow rate. Also, IUnknown has gotten his venturi to work with an Eheim, after changing to a different venturi model. (I'm querying him for details in another thread over at APC. I'll post anything I learn here as I think this is a good methodology).

 

[IUnknown]

Tom, should we be concerned with tech bulletin #2 for any reason,
Mazzei Injector Corp. - Technical Bulletins

This was the response I got from Mazzei,

This pump is below our testing point of 5 psi of inlet pressure. Depending on you backpressure, which I'm assuming is low if you have the 287 working at 2 psi inlet pressure, you could possibly use a 584. Because this is below our testing points I can not tell you where exactly this will work but somewhere around 400 l/hr at 200-250 mbar is my assumption. You can get this model in either 3/4" (584) or 1/2" (584-C). If you have any questions, please do not hesitate to contact me.

The thing with having the mazzei close to the cannister filter is that 1' of head pressure (pressure from gravity pulling on water) is a lot for the injector. It works, but it works better the higher up you install the injector. Basically we are aiming for 0 pressure on the outlet of the injector, and a lot of pressure on the inlet (water going into the injector).

You can give the pumps a try. From my experience they are not engineered to deal with the backpressure. Here are my older post,

DIY In-Line Micro-bubbler - Page 6 - The Planted Tank Forum

Also, it seems the pump driving the venturi is a big variable in all of this since the stronger the pump, the more pressure on the inlet side. Is this more of a trial and error process or is there a BKM (best known method) established?

The thing is some pumps are engineer in a way that they can't deal with back pressure. They could have a flow rate of 1000gpm, but you add a restriction, and the impeller doesn't move any water.

 

[Tom Barr]

The issue with asking them is for our application, it is much different from the normal stuff, these are used on huge systems typically.

They have high flow and head pressures etc.

I use the sump drive and feed into the return pump, I've done this since I guess, 15 or more years ago. I used reactor tubes then.

I think if you look and think about those venturi aspirators you see on powerheads, do they resist flow as much? No.
Where are they placed though?

I think placing the venturi near the top, within 1 ft or less, a few inches would be even better, would be ideal and better.

Canister filters are designed to be less influenced by head pressure than sump pumps. They are more efficient in terms of less noise, heat and electricity for this reason.

The Rio HP pumps I've used for 4 venturis I've done for 2 different tanks, they work fine, then the bubbles are ground up secondarily by the return pump and
there is no head pressure other than the venturi.

You can use the larger canister, But it might be better to use a dedicated pump.
I think you will lose the benefits of the venturi at lower flow rates/pressures, and at higher levels, this may only be suitable for sump driven systems.
For low flow, the Cal lab's in line bubbler might be a better solution(but only 160GPH max flow).
But it's all glass, breaking easily, and DIY is not as simple, then you need to clean the disc as well.

I think you are going to find trade offs here, whether they are good or not is really your call, I like the venturis a lot for larger systems.
Much better than the disc. You can use a disc in a sump by feeding ti directly into the return also.

One area that venturis and the like have been used a lot to drive more gas in water: marine skimmers, they have spent a lot more time and resources in that area, but realize you will never sell a CO2 item for 400$ to diffuse into a 100 gal tank either.............and they typically have massive pumps driving them.

Still, a needle wheel powerhead would be a nice very simple internal version or sump method.

In line methods are another matter.
Amano went with the disc for this reason I believe and so he could watch the mist and it's effects in the tank.

He never said this, but based on observing a tank and playing with a few different methods, it's easy to justify such a conclusion.
For a tank in the 80 gal and up range, sumps are nice items.


Regards,
Tom Barr





Regards,
Tom Barr

 

[tefsom85]

Restriction sizes on Mazzei

I am curious about the flow size restrictions on the different models of the venturi's. I measured my venturi's restriction to be 7/64" which would explain the severe drop in flow - ~1/2" tubing size restricted down to ~1/8". I'm guessing the larger models, such as the 584/684/etc have bigger restriction sizes which would have less impedence to the natural flow through the venturi. I queried Mazzei about this and they are unwilling to give the restriction sizes of their various models as it's proprietary (don't know why as a serious competitor could easily just buy them and measure). I know Iunknown has ordered 584 and 684 models - I'll ask him about the sizing of those models.

My assumption is, and maybe I am incorrect, is that if I find a venturi with the restriction closer to the tubing size, flow/performance will be much better. Flow will be better due to less resistance and performance should be better with much greater flow to shear the CO2 (assuming that the injected CO2 does not limit the flow significantly). Are these fair assumptions?

 

[Tom Barr]

I have no doubt at all with some testing and tweaking, various venturis could be utilized for aquarium CO2 injection.

That said, tweaking these to work well for the various sizes we might need for our application is another matter. Generally we are using their application(higher flows/aquaculture etc) and adapting it to ours which tends to be much smaller.

The idea is a worthwhile one.
No crap in the tank, in line, no maintenance, highly effective as well as directional.

The economics are also good if a more market focus product was produced specifically for the hobby. Running maybe 20-35$ for sm/med/lg.

That's where the future should likely end up here.

Regards,
Tom Barr