Bell Siphon questions

[JRComito]

I recently designed and built my siphon, and I wonder how important it is to have a "gravel guard" around it. The other question is how much more effective is a siphon with a snorkel versus without one? I am testing with a tank of water without gravel, so I am aware that the flow rate is going to change. Is it enough to restrict the siphon's flow? Is having the gravel in the bed going to have a big impact on flow, and should I "over-build" the siphon to be ready for that?

Thanks for any help.

[Rob Torcellini]

The gravel guard is very important.  It keeps any small stones from getting sucked up into the plumbing, and it allows you to remove the bell for maintenance.  Here's one of my videos about some of my system maintenance...plenty of roots to get in there!  http://youtu.be/Jf8Lxpl_8z8

The breather tube is always a good debate topic.  I personally like them since I find they help to make a nice clean break without sucking a lot of air through the bottom of the bell.  I've also modified the tube to assist with making sure the break works better every time.  http://youtu.be/4hHRe3KJfoY

[Jim Hall]

A second on the gravel guard. I just spent an hour messing with my siphon and in the end, it was a couple small pieces of cinder that were stuck in the drain pipe and wedged with some root matter. Usually I will clear the pipe with a stick as a first measure. Guess my mind is on just getting things to work so I can head for the aquaponics conference tomorrow. :P

[Robert Rowe]

My advice is to build the classic Bell Siphon, then use it. Don"t change anything. Make it work and then modify the design to see what happens. It can be improved and a minor change; like leaving the one or two elbows of the tail race can ruin your day. 

[Phil Slaton]

What those guys said above.  Don't mess with perfection.

[John Cubit]

Yes to the guard, but on a side not be careful if you make your own be sure to match it to the media.  Meaning if you have a flat rock or pebbled gravel or Hydroton or Hydrocorn, your guard needs to match.  I did not pay attention to this and used Hydrocorn, a less consistent size cousin of Hydroton and in 2 days my guard was full of media, the bell was blocked and the downspout was plugged at an elbow, all because a set of holes that were fine before were now too large.  I now have slits not holes in my current guard.  I would make a few and once you physically have the media so you can see what condition it is in you can decide on an appropriate guard.

I was glad this was a test bed and not the real thing but now I am 3 days away from planting my cuttings and some seeds for the next level of testing.  Just need to get the flow in under control so the siphon does keep working (another thread here)

[Jim Fisk]

You can't go wrong with this design. Bullet proof. Picture worth a thousand words: (Don't glue it up though. Just pop the parts together so you can adjust height later. My bad:-) I use an "o" ring below the tote bottom and the only place I now use electrical (grey) pvc: the female threaded adapter below the "o" ring so as to avoid the taper and that allows you to tighten right to the gb bottom. Grey (electrical) pvc has fire retardant chems so limit their use in your system as we have no idea what they are. Here the exposure is about 1/16". Not enough to worry about. Use water pvc (white) for the male TA (threaded adapter). This is based on the Affnan design (although he is not the first. A man named Crapper designed our toilets based on Bernoulli's work as well) and works awesome. I cut the slots in the gravel guard on the chop saw in a spiral pattern for strength. You can find a 1" to 2" adapter online but at the box stores you must do it in 2 steps as in the picture. You'll need a knob on top of the bell like the last pic in order to lift the bell out when needed. Also there is absolutely no need to cut the gravel guard slots past the half way mark. A waste of time and it weakens it. Have fun. Oh, also I should mention: I had a cut worm hiding in this lettuce patch and brainstorming I cut a 2" section of 2" pvc, stuck it in the top of the "funnel" and flooded the gb. Up he popped. Make sure it stays below the gb walls as you WILL get distracted and flood the floor if it is higher

[JRComito]

Many thanks to all who have replied. I will be redesigning the "teeth" on my cover tube and I will be including the gravel guard once I procure some larger PVC. I will try without the snorkel for now as I had mine working, but not Every time, and that is what I'm after. I am not always around to jiggle the thing you know? I'll add it if I need to. I'm getting excited about adding my gravel! Can't wait to plant it out! Thanks again for all of the great advice.

[TCLynx]

Right on.

Yes, gravel guards should always be used.  Always make your drains accessible since you will eventually need to clean them, roots will go where they will and you sometimes need to remove them.

[TCLynx]

As to the siphon.  Things like the funnel, restrictions on the drain line, extra elbows and traps at the bottom, the breather tubes etc are really all just ways to improve on the basic siphon function.

It is always best to try the most basic version out first to see if it works and then based on how it behaves you add the other bits to improve on it to suit your situation.  For instance if your siphon is having trouble starting, the funnel or the trap or restriction on the drain are more likely to help and the breather tube is only needed if your siphon isn't stopping properly.  Often once you add the trap at the bottom, you HAVE to add the breather tube since the siphon will have a very difficult time sucking a gulp of air if there is a trap.

[Robert Rowe]

TCLynx said:

As to the siphon.  Things like the funnel, restrictions on the drain line, extra elbows and traps at the bottom, the breather tubes etc are really all just ways to improve on the basic siphon function.

It is always best to try the most basic version out first to see if it works and then based on how it behaves you add the other bits to improve on it to suit your situation.  For instance if your siphon is having trouble starting, the funnel or the trap or restriction on the drain are more likely to help and the breather tube is only needed if your siphon isn't stopping properly.  Often once you add the trap at the bottom, you HAVE to add the breather tube since the siphon will have a very difficult time sucking a gulp of air if there is a trap.

The main cause of problems starting the siphon action is inadequete water flow.Remove kinks or other line restrictions or iselarger pipe.

Poor performance on shut off can depend on the positioning of what ever elbows you have in the tail race. it's important to have each elbow level or slightly lower on the downstream end to ensure the shut off air can flow up the pipe to break the siphon.

My experiance has shown that the bottom of the tail race should be into a larger pipe ensuring the siphon stay mehanically seperate from the drain. i.e. a 1" tail race with a 45 elbow into a 2" 45 elbow.

[Jim Fisk]

Also don't forget plumbing 101. Provide a vent on that 1.5 - 2" main drain. That is what the roof vents are on your house. Otherwise the siphon action on your sinks, tubs, showers, etc. would not break suction until your traps were empty. Of course there should be no "traps" in your ap system, just down hill slopes. (traps on your home system are there to keep sewer gas from backing up into your home. We don't expect "sewer gas" in our ap systems:-) God forbid! But none the less if the drains get fully loaded and run say 20' to the sump like mine do you had better have a vent somewhere near the beginning of the run to break that siphon and then you should have no problem with you siphons shutting off. I have 2 90's in each siphon drain and have never had a siphon "hang" in 2 mos of steady op. Here is a pic of my system vent which now runs just above the top of the grow beds :

If you are dumping straight into the fish tank you should never have a problem. Keep in mind though that flow rate also greatly effects start and break. Not enough flow and your siphon may not start "make" and too much flow and it won't "break". A good siphon design will be pretty forgiving. I run the 1" siphon lines right into the 1.5" drain line but the need for a vent was immediately apparent the first time I ran the system. It was a "well duh" moment

TCLynx said:

My experiance has shown that the bottom of the tail race should be into a larger pipe ensuring the siphon stay mehanically seperate from the drain. i.e. a 1" tail race with a 45 elbow into a 2" 45 elbow.

[JRComito]

Well my siphon worked fine last night with 2/3 of the gravel in. This morning I filled it with the remaining gravel, and now the siphon won't start. I am running a 3/4" bulkhead with a 3/4" standpipe, a 2" bell housing fitted with a 1/4"mpt to a 3/8 barb for the snorkel. I need to get inside to my pc so I can post some photos.