Pond Boss Forums INTRO Questions & Observations Ok, I dont get this siphon stuff

Jersey,

These are the photos I took during construction. I will try to add some more the next time I am down there...to help put the size into perspective - the dozer you see in some of the pictures is a Cat D8 and the dam is about 550 - 600 feet across. The spillway is wide enough for the D8 to drive thru and about 5 foot deep from the top of the dam.

http://i4.photobucket.com/albums/y117/darnold01/NewDrainPipeHole2.jpg

http://i4.photobucket.com/albums/y117/darnold01/NewDrainPipehole.jpg

http://i4.photobucket.com/albums/y117/darnold01/NewSpillway.jpg

http://i4.photobucket.com/albums/y117/darnold01/Dam2.jpg

http://i4.photobucket.com/albums/y117/darnold01/Damcleanedoff.jpg

http://i4.photobucket.com/albums/y117/darnold01/Damfromwestside.jpg

http://i4.photobucket.com/albums/y117/darnold01/FinishedDamwithPierandBridge.jpg

Theo,
Not meaning to beat a dead horse, but the inlet height and the crest height mean nothing to a siphon. It's the pond water level and the outlet that matter. I think you meant that.

Here is a (very) simple drawing of how my drain pipe is designed. The inlet is on the left side.

http://i4.photobucket.com/albums/y117/darnold01/drainpipe.jpg

Alligator,
How does your vent pipe ever get closed? It looks to me like the water would have to flow over your dam in order to close the vent. Shouldn't you shape the vent like an upside down U with the open end in the water at the desired level?

Jersey,

My vent pipe will close when the water level rises above the top of the 12" pipe. It is the same principle as the "upside down U" - except simpler. In this design there is a lot less pipe sticking up out of the ground (and a lot less pipe to break with your mower, tractor...etc.)

Gator

Alligator
I'm with Jersey from your drawing the water would flow over the dam before it would start siphoning.
The 4" pipe has to become clogged either with water or debris before a siphon would occur.
In the case of debris it would drain the pond.

That's how the drawing looks anyway.

All,

First, let me apologize to my high-school drafting teacher...Mr. Lambert, you taught me better than that. But hey, that was 25 years ago!

I re-drew the drainpipe to be more precise:
http://i4.photobucket.com/albums/y117/darnold01/drainpiperevised.jpg


The key here is that the 4" pipe has holes in it - like a sewer field line pipe. Therefore, as soon as the water hits the mark where the 4" pipe joint goes into at 12" pipe (or more accurately, the first hole in the 4� up from the joint) the siphon will be made. Since the 4" is full of holes � the water does not have to flow over the top to make the siphon.

The design of having holes in the 4" pipe keeps debris out of the system much like an inlet cover. This is much simpler than the �upside down u� design but works on the same principle.

Gator,

I understand your description and drawing but I think you will find a problem with the way it is setup. I may be wrong, but any hole allowing water to enter the 4" pipe will not be enough to completely seal off the 4" pipe starting the siphon. The 4" pipe would have to be completely covered or underwater for the siphon to start.

The slightest amount of air entering the 4" pipe will break the siphon or prevent it from starting.
Was there a reason you went to 4" pipe? A 1/2" "U" will do the necessary job of starting the siphon once the water level rises to block off any air entering it.

I hope your pond fills up soon and please let us know how the 4" works.

Dan

Gator,

I should have said that once the siphon starts it will suck the water out of the 4" pipe faster than the hole(s) can can allow it to enter, thus allowing air to break the seal stopping the siphon.

You could quickly make a miniture "model" out of 1/2" or 3/4" PVC with the same basic design and put it in a tub or bowl of water and see if there is a problem.

Good luck.

Dan

Dan,

I had the same thoughts as you, however, my pond guy - "has done 30 or 40 fo these" claims it works. I looked at a couple of his ponds and he seems to check out, overall. Havent seen one in sipohn mode yet.

I agree the question of the design is: Will there be a siphon when the water hits the 4" pipe OR will it suck air and just drain...(not sure I will be able to visually see much difference?) hopefully I will find out soon. Not much rain in the forecast right now.

On the question of the size of the 4". I agree with you, a smaller pipe would work. I never really asked "why" a 4". I suppose that was based on avaialblity of the pipe joint and/or habits of my contractor. One thing I have noticed about contractors is that they seem to find what works for them and stick with it.

I suppose if the siphon doesnt engage as planned - I can cut the 4" pipe down or replace it...there is no real reason to have a pipe there other than to eliminate the hole from becoming clogged.

Gator,

That makes sense. After 30 or 40 I'm sure he knows what works and what does not. While you are waiting for your pond to fill it might be interesting to make a small model and test it in a tub of water to see if it is obvious why it works.

Keep us posted.

Dan

Dan,

Let me further qualify this siphon issue on my design.

The design in my system is referred to as a "Vaccum Breaker", therefore implying that it is designed to eliminate a siphon vs. create one. This is an interesting idea to ponder...AKA, the design on my system is to drain until the water level reaches the fill line, then ensure the vaccum is broken. It is not designed to automatically create a vaccum? Perhaps so. In the standard "upside down u", the design is to automatically create and disengage a siphon. Two different designs.

Alligator,
Yep, that's a vacuum breaker. It is designed to keep a siphon from ever happening. Looking at your new and improved drawing, it appears that you might get a siphon going just as the water starts flowing over the top of your dam, but with the amount of vacuum a 12" siphon can pull, you would probably get a nice whirlpool over the 4" pipe that would easily suck in enough air to break the siphon. Even if the 4" pipe is a foot under water, a whirlpool can suck in a lot of air. When this happens, the siphon will start, then it will suck in air and stop, then it will start again, then stop, and so on.

I design large aquarium systems that use the same siphon system we have been discussing here. Most use a 1 1/2 inch siphon tube with a 1/2" vent. With this I can get a whirlpool to suck air down 3-4 inches below the surface. You can only imagine what a 12" siphon with a 4" vent can do. A 12" pipe is 64 times as big as a 1 1/2 inch pipe.

Your system would be very easy to convert to a real siphon system. If you want to wait and see what it does, I just hope you have a well built emergency spillway. If not, get yourself some kind of cap to temporarily seal off the vent if the water gets too high. Just remember to remove the cap before your pond is empty!

My "improved" drawing may not be to scale either. I need to re-look at the length of the 4" pipe to see how tall it is. I recall that the top of the 4" pipe is significantly below my overall dam height + I think it is well below my emergency spillway too. Needs a look see and test when lake is full.

My Emergency Spillway is approximately 10' wide by 5' deep

Looking back, I think my first inclination was right - I dont get this siphon stuff.

But I think I now understand much better, thanks guys.

OK Dan and Jersey,

Unfortunatly my second drawing is fairly accurate. I think the 4" siphon pipe is too tall and will cause a big whirlpool as mentioned above which will take the lake level around the same height as the spillway. Additionally the 4" pipe dosnt have nearly enough holes in it.

I have Vaccum Breaker and doubtful I will ever draw a siphon in current design. The 4" pipe is way too tall. Hello spillway. I'm thinking that I'm going to pull out the 4" and either cut it down or replace with "upside Down U" to make sure I pushing as much water as possible thru the pipe.

Can anyone tell me a way to calculate the difference in thru-put for a drain vs. siphon? Is is 1x, 2x...?

Alligator, I saw a chart a couple of weeks back that showed the difference between a siphon and a plain ol' pipe. I can't find it anywhere now. I thought I saw it on ponddampiping.com but I don't see it there now. You know they say the memory is the second thing to go...

Anyway it seems to me it was about 6 times as much water. I calculated the flow of a 12" siphon (I will have 2 of them) and it was 355,000 gallons per hour each.

I think if you will make a 4" upside down U for your system, you will one day be glad you did. At least have one made that you can pop on there pretty quick.

burgermiester posted this link on another thread:
http://cotton.pi.csiro.au/Assets/PDFFiles/WATERpak/WPAp9_11.pdf

Thanks for the link Ric, and for the input. I have a little work to do on my Vaccum Braker if it is going to work like a Siphon.

Alligator,

What you have there is a "siphon preventer". I think careful communication with your pond guy will clear up the miscommunication.