VENTURI QUESTION, HELP NEEDED

[Mmathis]

I have the water from my pump entering the SKIPPY from the top. Have a "Y" fitting where the tubing enters the down-pipe. Thought I would make a Venturi, so drilled a small hole in a cap and inserted a piece of smaller diameter tubing (don't know the measurements, but is about the diameter of a jumbo-sized straw). Have the tubing inserted past the point where water enters the main tubing.

Well, not sure I've done it correctly, as there is frequent "burping" of water back up the "Venturi" tube -- that's the best way I can describe it, 'cause it looks & sounds like a burp! Even without the cap & small tube, when I leave it 100% open to the air, it still does this.

I don't think this is normal for it to be a Venturi, as it should be sucking air in, not spitting it back out. So what have I done wrong & how can I fix it? And PLEASE don't refer me to a jillion sites, 'cause that's where I came from and I obviously have missed something important along the way. I have a VERY BASIC grasp of how this is supposed to work....

 

[multifasited]

BEEN THERE DONE THAT GOT THE TEE SHIRT,LOST THE HAT ,What size pipe are you using ,how far are you trying to go after the venturi? What size pump ? Your trial method works ,marginally on small pipes 1/2"-1" I perfer to take a short pc. pipe 3" long ,filled solid w/bondo .,runny ,to get the air bubbles out ,seal bottom ,set on plastic bag fill up leave slight dome on top,let cure , drill a 1/4" hole 1 3/4' down the pipe 1/2 way [only] thru the pipe,use step drill centered from both ends ,after you trim sq.both ends,w/ drill press,want to create funnel ,on both ends ,tapering to center and merging w/ 5/16"to 3/8" hole thru both funnels [looks like a hour glass,now ,w/a 1/4'hole for a 1/4" tubing slip between two couplings ,now you have very powerfull venturi ,I keep mine horizonal hole pointing up ,if you don't like it it's easy to remove replace w/3" pc pipe move to new location ,tests and trails a pc. of cake .

 

[sissy]

I have venturis that came with my pumps Not sure if seeing one will help nut this one is very small and a hose to go on it needs to be 1/16 size if I remember and in the elbow coming out of my one filter tank I drilled a hole to make on and it had to be an extreme angle .I saw it on you tube ,how to do it .But his did not burp but mine does a little

 

[Mmathis]

BEEN THERE DONE THAT GOT THE TEE SHIRT,LOST THE HAT ,What size pipe are you using ,how far are you trying to go after the venturi? What size pump ?

Whoa, Multi, you've already lost me. I'm using 1-1/2" PVC pipe, but will have to go out and find/measure the skinny tubing (or find the drill bit I used to know what size it is). My pump is 3600 GPH, but I have it cranked way down going into my SKIPPY.

One site I read (and watched a YOUTUBE video) made it look so very simple -- just drill a hole, stick in a tube and you've got a Venturi. But then everything else I read got more technical, which made me wonder what part of "physics" was I not comprehending. Guess I need to watch some more BIG BANG THEORY episodes

 

[sissy]

Guess you are not the only one ,but mine has worked pretty good and it is a 2 inch abs pipe and I put a hose in it and I really see alot when I add the aerator hose in the tubing with the air pump going it really makes the thing bubble alot .I did put a back flow preventer on the air line just in case

 

[multifasited]

Venturi is a compromise ,venturi sucks open air into water stream .putting an air pump line into a water flow is a totally different animal ,loses occur in both ,cases ,you have to pick you poison ,in some cases flow losses are ok and added air is beneficial .head pressure changes ,really very selective of where and how to use .venturi as described reduces the flow from 1/2" to 3/8" pressure increases creates vaccumn suchs in air replacing water ,the one I talked about should create about 12 psi of vaccumn very strong for its size ,most like your discribing create may be 2 psi at most larger pipes larger tapers like 1 1/2" taper to 3/4' hour glass shape longer taper pc would probably 8" long w 1/2" air inlet drilled at begining of expanding past center ,fun to play with,funtional in the right place w/ the right application .

 

[Mmathis]

Never got around to investigating the size of my tubing, but think it's 3/8".

But, left for a week, and since I've been back I haven't noticed the burping at all. And a periodic check of the tubing and I'm not seeing any moisture or indication of recent moisture on or around the tube or fitting like was happening with the burping.

 

[sissy]

When i drilled my pipe out I just drilled it at a 45 degree angle

 

[koiguy1969]

for a venturi to work best you need to match flow with venturi pipe size... you want a smaller pipe so the water is flowing thru with more pressure. this creates more vaccuum to pull in air. the less flow the smaller the pipe. anyways here is my thread on easy to make venturis. experimenting with size/flow ratio can get you the results your looking for. remember the further down your trying to push that air the larger the bubbles will be as they combine in the piping. this may help you...
http://www.gardenpon...enturi-t-style/
i would like to add that a venturi installed on a downflow filter is likely much more effeicient. since the majority of aeration takes place at the waters surface.