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26 Posts
Discussion Starter · #1 · (Edited)
I have updated my overflow siphon. Here is what it looks like now:

It looks better in the water:

I decided to do away with a self priming venturi because it would spray bubbles into the tank every few seconds. It has run several days without any bubble accumulation, but i must admit I've only tested flow ranging from 100-150gph for extended periods.
I made the intake height and tank hook height adjustable with a nylon set screw. This lets me tweak the water level without excessive air being sucked down.

Here is my biggest change:

I took a lesson from dual stand pipes to completely eliminate the "glug glug" or toilet flush noise. I just close down the gate valve until the lower pipe no longer sucks any air.
You can hear how quiet it is here:
The trickle you hear is just the water falling about an inch down the pipe inside.

I am pretty happy with my results now and am going to look into putting it on a tank. I wish I could have made it a little more compact and keep the same flow capacity, but this is as tight as I could manage to push the bend radius of acrylic without creasing.

Here is the old post:
I don't even have a tank with a sump, but for some reason I became fixated with trying to make an overflow siphon that would look presentable in a rimless tank. Here is my DIY Mame overflow ripoff attempt:

And here it is in action

I will do some more fiddling, because right now I need to pump about 100gph for the venturi to self-prime the siphon but the it maxes out at about 150gph. I would not trust such a small window of flow to not dump water all over my floor. I also need to cut down on some of that noise on the siphon break.

Here's how I made it:
I started with 1" acrylic tubing. To keep it from collapsing while bending I stuffed it with 3/4" silicon tubing. I then filled the tubing with sand to make it a little more rigid.

From there I would heat the tubing with a heat gun and carefully bend it. The tightest bend radius I could manage without the pipe getting creases was about 2.5" on center.

And here is is with all the main bends done:

I untied the end of the silicon tube and dumped out all the sand so I could pull it out. Well that is what I was hoping anyway. The tubing would not budge until I worked some mineral oil in there.

Here we go, finally got it out:

From here I started to drill a hole in the top of the loop for a siphon break. Of course, cracks started to form. In an attempt to salvage all the time I spent bending the tube, I heated up the pilot hole and stretched it out enough to fit 1/2" acrylic tubing. I glued the tubing in place with some number 4 cement, then reinforced it with a little bead of number 16 cement.

I had originally planned to have some airline feed through this half inch pipe up to the top of the siphon for priming like this:

But air bubbles liked sticking around just downstream of the opening of the tube, so I decided to feed it in the intake side.

On the intake side I had a problem with air getting dragged down the pipe. I found flaring the end like a blunderbuss helped with that.

From here I plan to work on:
a more elegant implementation of the priming tube
less return flow required to self prime
a better placement for the siphon break
tighter pipe bend radius or less deformation on the bend

I would appreciate any input on the design or advice on making acrylic bend to my will.

26 Posts
Discussion Starter · #4 ·
I depending how busy I am with work, I might be able to build a better version within the week. I'll keep this thread updated.

As for the picture in my car. I have some driveway moments when I want to finish listening to a radio broadcast. I'll usually fiddle with something at the same time.
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