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Fluval Diffuser Restriction

Henry

Member
Joined
20 Mar 2013
Messages
899
Location
Salford
My current setup consists of a disposable welder bottle and regulator from Machine Mart, AE needle valve, check valve and a Fluval 88g diffuser. I am wanting to increase the bubble rate, but I can't seem to get any higher than 2 bps. If I release the pressure in the line, I can increase it temporarily, shortly slowing to 2 bps again. Is this because of the small size of the diffuser plate?
 
I think you may be right. Luckily I've got another canisterin reserve so I'll give it a go when I get home.

How fine a mist is it supposed to give off? If the flow is switched off, a number of bubbles will reach the surface. Is this normal?
 
I've moved the diffuser. I've got it running into a Hagen Mini with the diffuser mod on it, the bubbles from that then go into the spraybar or the filter inlet. 100% diffusion!

I changed the CO2 tank over to a new one and still have the same problem. If I disconnect the line to the diffuser the bubble counter looks like a boiling pan! The only thing I can think of is the check valve isn't opening properly. If so, its able to hold back some serious pressure! I'll go over the whole system tomorrow and see.
 
You have helped, it's all a process of elimination with these things. I'm just pleased its not the cannister running out since its only been going 6 weeks. I presume I just soak it in bleach? Seems odd that it was blocked straight out of the packet (unless, of course, it is indeed the check valve).
 
Still having trouble with this. The check valve is fine, and I've cleaned the plate with bleach then glutaraldehyde. Is the plate just too small for the amount of gas I'm wanting to put through it?

The bubbles seem to be mostly coming from the edge of the plate.

Edit: I've just ordered a replacement plate, and another whole diffuser. If it turns out to be a faulty plate, I'll replace it. If it's a pressure issue because of plate size, I'll rig a second diffuser to the system.
 
I use the same diffuser and I purchased a spare ceramic plate to swap out when the one in use became grubby.
I noticed that apart from it being difficult to unscrew the bottom of the diffuser that after I changed the disc over as with you I only had large bubbles coming out or forming around the inside edge.
After I had tightened up the bottom of the diffuser with as much strength as I posses it returned to a nice mist again.
It may be worth checking that the rubber seal is not damaged and the disc and seal are seated correctly, I'm not sure but I think the rubber seal can go either way up.
I am pushing about 1 bar through it with at least 3 bps although it seemed to function fine with around 0.5 bar
 
I have tightened it to the point where I struggle for 10 minutes to open it again.
 
I've now tried 3 Fluval diffusers, all of which cause the same problem. This is incredibly frustrating, since a lot of people say these are the best. I can't get past 2bps which is causing algae in my tank!
 
I can get over 4bps with a coke bottle diy co2 reactor and my fluval ceramic difuser (and way more than that with my 2kg FE)

So theres insufficeint pressure in the bottle or the regulator is restricting the flow.
 
If the diffuser is detached, gas flies out at a high rate, it's only once it's reached the diffuser that I get back pressure. I refuse to believe that a ceramic plate can hold back pressure from a welding CO2 bottle!
 
Just an idea but what type of tubing are you using?
If its normal air line it may be expanding/leaking, I am probably clutching at straws mind.
I had a look and the ceramic plate and rubber seal only go in one way not either way as I said before.
 
It's strong black PVC tubing, so no possibility of it expanding. I've also eliminated any possible leaks. It's quite annoying. If I split the line evenly, the excess gas seems to find it's way to the second diffuser. grr
 
I only split the line as a solution to the original problem. It didn't work. I've since switched to feeding the CO2 hose into an Elite Mini via an airstone.
 
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