Backyard Aquaponics
A place to discuss aquaponics

Could be the elbow - I've found with the elbow in the wrong place it works and then doesn't work - experiment

I haven't read the tread so sorry if this is not relavent. But a ball valve going straight into a T causes a venturi, one end of the T is above the water level and the other end below.

I've changed tips (yes, it was pointing in the right direction), I've moved the elbow and created a really long pipe to feed into the venturi and still just not there. I've ordered a venturi and we'll see if that fares any better. I should get it in about 36 hours so I'll have to wait and see. For now I put an airstone and pump to circulate the media.

Just installed the professional venturi and while it produced air it just isn't enough to move the biomedia. I'm going to stick with the airstone until I learn more about what I'm doing.

Not sure if it's related to the water, size of the venturi or something else.

Thanks everyone for your help.

Trust me it is related to the venturi

Stuart, have any recommendations or a link to someone in the US? I'm looking at the one mentioned in RobBob's video now.

For a lot of these things you can take your lead from the RAS industry. They do use venturis but their application is limited to specialised roles or for particular reasons due to something specific about a system. Watt for watt you get better O2 transfer with air stones, trickle towers, baki showers or many other methods or components.

For a backyarder the only advantage I see is the capital cost in not having to buy a second pump, a larger pump or an air pump. Having said that the extra electiricity costs generally (not always but often) eat up any savings with a couple of years.

bdornis,

From what i can see the only problem you have is that your air intake hose is way way to big,
i think you need to reduce the size of the air intake hose by at least half.

Do that and i am pretty sure you will achieve what your looking for, if you have a close look at Rob's its only a very small diameter air hose.

Stuart, the primary reason for going with a venturi was to keep the neighbor happy. I bought a couple quiet pumps that didn't output enough air. One that actually works is a bit loud. He says it's fine but I was hoping to be a little quieter. I'm quite hard of hearing so if I can hear it then it's probably pretty loud. (the airpump sits on a soft sponge to prevent vibration rattling) The venturi was silent (both professional and home made) which was a huge plus in my book.

Porter, the professional one I bought has a small diameter intake. It worked but didn't provide the air volume I was hoping for. I might look at some others or just play around some more fiddling here and there but for now I'm going to use the airstone.

There is another reason I hadn't thought of.

Joel had a silencer for his FT inlets. From memory it was a smaller delivery pipe jetting water into the FT which entrained a lot of air into the tank. This was surrounded by a larger pipe which cut down the noise.

If you got the relative sizes of the two pipes right with the flow the entrained air would be taken down the larger pipe and expelled at the bottom of the FT. You would need enough velocity in the larger pipe to overcome the boyauncy of the air bubbles.

For an moving bed filter you could use a water pump to push water up through the filter and then down through another trickle filter or baki shower.

all good mate, no worries.

I'm only guessing as I don't have a venturi.

But as I understand the reduced pressure caused by the increased velocity causes the air to get "sucked in".

if you have a high pressure in the pipe like going from a pump to the bottom of the tank the reduced pressure in the venturi may still be higher than atmospheric pressure so the air may not get "sucked in"?

So if the pipe went up so the venturi was at a higher level (thus reducing the static head) and then down to the RFF maybe the venturi would suck?

proper venturis have a specific shape thus increasing efficiency.

slowboat, yeah. I've been debating whether or not to move the inlet a bit higher.

I am using a lasco spa jet venturi plumbed through the bottom of my media filter via 3700 liter pump. It had half a meter head to the venturi, but was unable to create the pressure differential need to pull air into the line. I ended up plumbing up and over the the filter, 1.5 meters of head, and was able to get a decent amount of bubbles and movement in the filter. Of course my LPH dropped to about 1500, which worked out great in regards to retention time in my settling tank. I ended up having to add an airstone to get enough movement to slough off old bacteria. I will try plumbing through the bottom again when the funds for a larger pump presents itself. I am thinking it will probably take a 20000LPH pump to do the job.