Backyard Aquaponics
A place to discuss aquaponics

Can some one explain a venturi drain system to me? I've heard it mentioned several places but I'm not sure how they are supposed to work or how to make one. I know about venturis that you attach to a pump to add air into a tank or increase the amount of water being moved around but what is a venturi drain?
Does it require a pump or air pump or can it function with gravity?

TC, AFAIK imagine a pipe in pipe siphon with the cap taken off the top. The outer pipe has holes at the bottom so that poo goes in, up the outer pipe, then overflowing into the center (stand) pipe. The idea is to pull solids from the bottom of the tank using the outer pipe and still setting the tank level with the inner pipe's top.

If your tank doesn't have a bottom drain you can get a similar effect by having a vertical pipe go to the bottom (with holes or crenellations to let the poo in), then up to a tee, then over to the tank's side and out. See Joel's CHIFT PIST system for this (or my system ala 2007's thread).

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I changed the bottom of my pipe recently as at least two fish got cut by the crenellations because my pipe didn't quite touch the bottom of the fish tank. I cut slits into a smaller diameter pipe using a miter saw and dropped this down into the vertical pipe. The slits let solids in without being a potential hazard for the fish, and it automatically adjusts to sit right on the tank bottom.

Ok, I guess I had the idea all along but was having trouble believing that what I was picturing would actually work to get the solids out. So here are some pictures gleaned from other threads.


Kinda hard to see with the green water.

I suppose in a way this is what I want to do in my waterfall tank. I need some sort of divider that can block water flow across the upper portion of the tank and force water from the bottom of the tank up and over the waterfall carrying solids with it. I just have to figure out where to get something like a giant cutting board that I can use for the purpose, then I need to figure out how to secure it into the tank so it doesn't move.

TC, here is a pic of Michael Ferrini's drawing...might help in showing you

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I have my 2 fish tanks set up as a venturi drain type and it is excellent....better to use in a round tank so that the swirling action will move all the crap into the centre and sucked out the drain...Mike had a hole in the side of his tank but I put one in the base...just an improvement on his design

If you want more pics, I can toss up a few of mine to give a better idea

Heres my versian of the shift pist or venturi drain its in the new square tank i am setting up its in 50 mm you will notice the elbows this always allows the vertical pipe to stay on the bottom and the tee piece is for overflow if the strainer at the bottom gets blocked

What sort of tanks could you use a venturi drain in?


It seems to me the Chift Pis system is one of the most foolproof and easiest to set up systems (comments disputing this are welcome).

Could you use a venturi drain in a bathtub or would the shape of the bathtub not be condusive to removing the solids?

I am guessing that at its worse it would be no different from having a pump in the fishtank, as that wouldn't pick up all the solids, would it?

In the aquaculture world, venturi draims are very common, particularly with circular tanks but I have seen them with hatchery raceways as well.

These are a few of the photos I took when I visited the Coleman Salmon Hatchery in Anderson, CA. They allow the public to visit but I went off-season and received a personal tour. They breed, raise the minnows, release and harvest the returning salmon, year after year. They also raise steelhead trout here as well. Interestingly enough, they have to use a reverse osmosis plant to clean the water before using it in the hatchery. I wanted to go in that facility but no one was available- perhaps next time. The water is actually cleaner after leaving the hatchery than when it enters the reverse osmosis system- this is mainly because they eliminate all viruses and bacteria but in addition, they remove heavy metals which are prevelant in Northern Calif. from the gold mining and logging operations. You would love their back up generator too- a steam locomotive. Unfortunately my camera's battery died before I could take a picture of it. I incorporated some of their techniques into my system, after all I already know it works.