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This is my 1st system and its been fun getting here. Still a lot to learn.

I'm using a 140 gallon feed tub as a FT and 4- 2 x 3 ft mixing trays as GB's. The media is cinder(lava), there's a lot of that here in Hawaii.

I've ganged the 4 GB together with 2" PVC with drains at the bottom. The drains are 2" shower drains. The system completes with an external siphon dumping back into the FT. The system cycles every 15 minutes and hasn't missed a beat for 2 weeks now(knock on wood).

I'm about done with the fishless cycling, just waiting for the nitrites to drop before adding fish.

Criticism and advice are totally welcome.

I'm trying to post pictures as well. Hope they show up.

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Hi Averan,

The bottom of my barrels are curved,so i put a pipe fitting through the base(male to female adapter) and glued a 4" pvc flange fitting which serves as a base for the bell siphon. This means that my siphon drains all the way down to its base but 2" of water remains at the bottom because of the height of the pipe fitting. You can make a raised base for the bell siphon even if the base of the bed is irregular.

Your barrels are probably level though.  ;)  Any standpipe I insert into the drain outlet inside my bed won't be vertical.

Hi Averan,

Actually one of my barrels is slightly tilted to one side, so i heated and bent the bed fitting about 10-12 degrees to get the base mounted on it to a vertical position. I did overcompensate the bend and my siphon leans as a result but i left it that way because it still works fine. PVC is fairly easy to heat, when you heat it stick a pipe into it and get it vertical with a level on its side. Mount the base at the lowest vertical point and build the siphon to fit. Or you can fly down here, grab some vacation time and have a visit


I reread your reply this morning and I noticed you are outside the parameters I recommended. The pipe size of the outer pipe should be twice the diameter of the siphon tube. If you want to use a 3/4" siphon tube use a 1-1/2" outer tube, not 2". It does make a difference. If you have the patience to try again this may work for you. I just built and tested a siphon using the pipe sizes you used and it's very inconsistent.

Averan said:

I just tried this external approach, but can't for the life of me get it to work.  I should have just stuck with my functioning loop siphon instead of trying to improve things!

In my setup I have 1" drain lines from the beds feeding into the 2" T of the external siphon, which empties through a 3/4" pipe.  I've gone through a zillion variations and configurations, affnan mods, etc, but the darn thing refuses to start and when I start it manually it refuses to break.

This week-long ordeal has left me wondering whether siphons really work!  What at first appears to be a simple science of simple technology turns out to be a complex art that might take a lifetime to master!!

I think I might have to start over from scratch with my plumbing....maybe a clean slate will help.

Hi Averan,

I too realize my post may have given the wrong impression,sorry. I meant at some point near the base of the pipe entering the GB, establish a plate fitting horizontally on the pipe to act as a base for the bell. In this way, no matter what angle the pipe is you'll create a level surface for the siphon to stand on.

Well, I tried the 1.5" T w/ 3/4" inner tube and while I can sometimes get it to start on its own, I can't for the life of me get it to stop!  I cannot afford to reduce the inflow coming into the bed, this will happen naturally over time though.  With all the difficulty I have had for more than a week now, I am having trouble believing that anyone can get a siphon to work.  And this isn't my first time!

What really confuses me, is that if I leave the cap off the siphon, it pulls/drains really really well.  Of course that's just an equilibrium overflow, but it seems to need a lot of air to achieve max flow rate.  If I let it fill up with the cap on, it doesn't want to start.  If I let it start overflowing with the cap off and get a good flow going, then as soon as I put the cap on the siphon starts.  I'm pretty sick and tired of fiddling with how much air space is at the top!  I've tried different heights for the inner pipe, I've tried different caps, I've tried adding 3/4"-1" flare at the top, I've tried adding a snorkel tube to the cap.....but nothing I've tried works.  I also revamped the rest of my drain line going to the sump to ensure it was downhill all the way.

I'm excited about the possibilities with this siphon design as it seems more precisely tunable and it drains very strongly and completely empties the bed.  The only thing I haven't done is to increase my drain lines from 3/4" to 1".  I have this thought that siphons should have a decent range of conditions under which they function, but this experience is teaching me that the opposite is most likely true!  For a given system, there seems to be only one specific siphon setup that is going to work.

That seemed to do the trick!

I've figured out that what is different about my system and causing me such trouble is that my drain pipe has a long run to the sump.  Even though it has a constant 2" per 5' drop, it doesn't have the immediate drop out of the siphon that everyone else's setups seem to have.  This first drop seems critical to getting enough force to create that vacuum in the siphon to make everything work.

The snorkel tube gets around that and lets my siphon break properly.


If I let the siphon drain tube go all the way to ground level straight out of the siphon, then run horizontal to the sump and jump back up the 1.5ft (height of sump tank) to get into the tank, will this work better?  Basically, I only have about 2ft. between the bottom of the media bed and the top of the sump (sump is above ground tank).  Currently, I run the drain pipe so that it constantly slopes downhill all the way to the sump, but this means no big drop out of the siphon.

Any thoughts before I buy more pipe and experiment?


Averan...just making sure...

You mentioned trying different are gluing/cementing them on to the pipe..'?' 

The bell 'must' be sealed. I have heard of folks just 'slipping' the cap on, then it doesn't start a siphon...or not as well...and is inconsistent

Both caps fit so snugly w/o any glue that I have to wear rubber gloves and apply a lot of force to remove them!  Also, I have sections of clear tubing in the drain line that allow me to watch when the siphon is pulling air in or not and I can definitely get a clean airless pull.  I've even duct-taped every connection from the outside just to check.  If I glue it I won't be able to make any adjustments, and I'm tired of the endless trips to the hardware store for replacement parts!  =)  That said, as I exhaust all other options, I may just have to try it.

The long drain run as well as the smaller drain lines from the beds to the siphon are probably the cause of your difficulty in getting a decisive start/stop on the siphon.


Your idea about having the drain go down then over to the sump then back up will only work if there is an air gap near the siphon,  Otherwise it's gonna become a huge trap and might stop the siphon from working at all.

I can now confirm that last part TC.  ;)

I think I'm down to my last resort....upsizing my final drain lines from 3/4" to 1".

Glueing everything together didn't help either.

Gotta keep the faith that I'll get it working some day.

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