Pond Boss
I've found a good price for 12" schedule 40, but I'm a little afraid of getting the glue applied and the pipe shoved together, before the glue sets up.

Using the SDR 35 with the rubber gaskets looks a lot simpler. But, will the rubber gaskets seal well enough for a siphon system? Is there a good chance that it might not seal and the siphon not work?

I've done a search on here on the SDR 35, but nothing came up.

Thanks in advance.
Hello, Stacy

My understanding of SDR 35 is that it's a gravity drainage pipe, not designed for pressure. It's usually buried in the ground, which helps support the gasket joints. The siphon system, while not building up pressure, does produce an extreme flow, and thrust, which might wreck havoc with the exposed gasket fittings of SDR 35. Glued joints are much more rigid.

You said, you found a good price on 12 inch schedule 40 PVC. Did you check the price of the fittings? It's astronomical!

From my understanding of siphons, the same size pipe used for a gravity drain will have a much higher flow rate when used in a siphon system. Thereby, allowing for the use of a smaller size pipe for a siphon. PVC pipe and fittings larger than 6 inch are really expensive.

Determine how much watershed your pond will have, and size your primary and secondary overflows accordingly.
SDR or "Standard Dimension Ratio" is a method of pressure rating piping. The SDR is the ratio of pipe diameter to wall thickness. An SDR 35 means that the outside diameter of the pipe is 35 times the wall thickness. A pipe with a high SDR # (thin wall compared to the pipe diameter) has a low-pressure rating and a pipe with a low SDR # (thick wall compared to the pipe diameter) has a high-pressure rating.

The SDR 35 has a very thin wall and will be flexible which is a good thing for sewer gravity drains but not something you want in your dam. As pipe goes I would not use this no matter the fitting type.

As for the fittings. All gasket joint piping should have thrust restraints to prevent movement. If these are done right they can be costly. Depending on the elevation difference in your siphon the velocities when siphon is activated can be quite high. The glued joints are more rigid and that is what you want.

I would use SCH 40 solid PVC with solvent weld joints.
As for time before glue sets up. You have a few seconds to get it together. If you apply glue and put that section together before moving to the next section you should have plenty of time. And the great thing about it, if you do mess up just cut the joint out and start over.

Like Gully Washer said you should determine the drainage area and size the siphon and secondary spillway accordingly.
I'm asking because I don't know how to figure it out. How much pressure would be in a siphon system that had open intake and open discharge? Water IS moving thru the system, but it's not like pumps are pushing it. I'd think you would have to worry more about it collapsing than bursting?
Stacy, I would stick with the schedule 40. We've installed a lot of them - all Sch 40 with the glued joints. Never had a problem with them. It's really easy. Just be sure to clean and prime the pipe ends prior to applying the glue.

About the SDR pipe, I've not run through the calculations myself, but you should be able to calculate the pressure in a siphon by using Bernoulli's equation. Once you get that pressure, compare it to the pressure rating of the SDR pipe. That will tell you for sure.
Thanks for all of the replies. I will use the schedule 40.

We finally closed on the property last week. We've moved our equipment, but too many little must do things have kept us from starting on the lake. This week I hope to lay out the lake and start removing or cutting tree's.

I hope when we are ready to move dirt, we'll still have enough moisture for compaction. We've been over five weeks with no rain.
I once lowered my pond using SDR. After gaining a 10-12 foot lift, it sounded like an explosion when the dam crossover pipe suddenly collapsed, leaving a 20' section of PVC looking like lay-flat drain hose.
I used 12" Sch 40 and when we put it together, we thought 3 of us would be able to handle it, but man were we surprised. It was no problem pushing fittings on the ends of the horizontal section. After priming and glueing for the next 20' stick, we picked it up and tried pushing it on, but could only get it a couple inches into the fitting and that was it.

So of course we all started freaking out and the contractor took off running down the backside of the dam and jumped into his excavator. It must have been a solid minute from when we started trying to push that thing in to when he got the machine in place. I would have bet a paycheck that there was no way that pipe would budge, but when he put the back of the bucket against the end of the pipe, it slid right in with no problem!

So from that point on, we just used the machine to push them together.
I think I remember reading an article that Mike Otto did for Pond Boss Magazine saying that over "X" inch dia of pipe, you needed equipment to push it together and hold it until the glue set up. I don't remember the size tho.....
I once installed a lot of large bore PVC pipe, indoors, in a confined space above a ceiling. In the beginning, it was like wrestling a greased pig. But, we quickly developed the following protocol, which made it somewhat easier to assemble.

Step-1: Mark the pipe cuts using a wrap-a-round marking guide, and cut the pipe as square as possible to ensure maximum surface adhesion of the joint.

Step-2: Using a file, grinder, or router, create a 1/4"-1/2" bevel on the end of the pipe. This bevel will make it easier to push the joint together, as well as ensuring equal distribution of the glue.

Step-3: Make alignment, and socket depth reference marks on the pipe prior to assembly. The marks will indicate when full penetration of the fitting's socket is achieved, and alignment is correct. Also, the marks will serve as a guide for applying the glue. Thus, ensuring the proper amount is applied.

Step-4: Place the pipe and fitting into position, making sure all surfaces are clean, with no burs or anything that will inhibit assembly.

Step-5: Strap two ratcheting cable come-a-longs onto opposite sides of the pipe, and pull out enough slack cable to wrap around the fitting.

Step-6: Apply liberal amounts of primer and SLOW SETTING / HEAY BODIED GLUE onto the pipe and fitting.

Step-7: Push the fitting onto the pipe as far as you can. Then, wrap the cables around the fitting and simultaneously crank the come-a-longs, evenly driving the fitting home. Let it stand for a few minutes before loosening come-a-longs, to prevent the fitting from pushing back.

Tip: Do not assemble the fittings dry, in an attempt to check your measurements. The fittings are very tight, and the friction makes it nearly impossible to separate them from the pipe.

Using heavy equipment to drive the fitting home, as vamaz suggested, is a good idea. If, you have a steady handed operator. lol
Ask TJ about dry fitting pipe and getting it back apart..... laugh
© Pond Boss Forum