Pond Boss Forums POND CONSTRUCTION Building a dam Cold water siphon discussion

Gents,

I have done an awful lot of reading on siphons on this site, and also on some others. There is not a whole lot of information on these systems in northern climates. I would like to install one of these systems in our puddle out front, but have some major concerns about how this system would hold up thru the cold winter months we get. I'm pretty sure I could defeat the trap freezing issue by using a 45 "wye" with a female adapter/screw-in cap. (this was suggested by lassig I believe in another thread)

Probably my biggest concern would be water freezing in the "inlet" side of the syphon right at water level. The fact that it wouldn't act as a primary spillway due to the "ice plug" doesn't bother me as much as the pipe possibly cracking due to said "ice plug". This type of failure could possibly create a constant flow in the middle of the dam.

I would love to implement one of these into our pond as a primary spillway (currently only have an earthen spillway) and also as a means of evacuating stagnant cold water. Anybody have one of these babies installed in a cold weather climate that sees significant ice that can report?

Thanks,

I have had up to 20" of ice on my pond with the siphon system installed and haven't seen any issues. But my siphon is under roughly 3' of dirt in the area where the water level is. Granted it is only 2' form the surface where is goes across the top of the dam but no water in there. Now the question is is 20" of ice significant?

I would say 20" is a good benchmark for our area. I would say there could be some potential for a heavier ice pack, but rarely. What size pond is your system installed on? How is it fed? Does your siphon continue to flow through January/February?

I would say continuous water movement would be your best chance against an ice plug in the inlet at water level? I say this, but then I think of all the flowing creeks around my place and how they manage to form over with ice during those long cold snaps.

pond is 1/2 to 5/8 of an acre and has never completely filled. So other then the one time I started up the siphon to drain the pond to do repairs it has never been used. So that could be one reason I don't see any issues. Realize that it was real close in June 11 to kicking in (it may have and I did't notice)and then the drought of '11 and '12 kicked in. We have had good rain this year but the pond is still 3' low. Was higher a month ago but the rain faucet has turned off again and the level is dripping again.

It sounds like you haven't gotten much use out of your siphon since installing. I know the dry weather has been rough on a lot of people. We were real dry last year, but this year has been a complete 180 so far. You can almost stand outside and watch the corn grow this year.

I found some good information on common PVC failure referring to freezing water/solution inside the pipe. Basically in a nut shell, radial expansion is limited, or constrained, by the pipe walls which forces the ice to expand longitudinally. Linear ice expansion will cause a build-up of pressure between inlet/outlet valves, and it is this pressure which will expand the pipe, causing the wall thickness to thin beyond spec. and ultimately to failure.

As long as there is a properly functioning vent (vent itself hasn't developed an ice/debris plug) radial expansion would be limited down to a non-issue. Those incorporating butterfly valves on their outlets and ball valves on their vents may want to be conscience of their position during freezing weather.

And ultimately, if you want to safeguard yourself from any possible radial expansion, splurge a little extra on the inlet pipe and go with SCH 80.

If you have aeration in your pond, you could also move the winter diffuser so that the water is kept open around the siphon. The water should be warm enough so the water in the siphon doesn't freeze.

Also a good option essup. I had thought of those that place small fish tank aerators near their dock piers to keep them from locking into the ice through the winter. Unfortunately, I am not able to aerate due to the fact that I have a closed loop geothermal system sunk into the bottom of my pond.

In my case, I figure the siphon system won't displace enough water to make much of a temperature difference on the bottom. I would love to aerate, but I'm afraid of what might happen to the thermodynamics that are required for our system to function at the proper efficiencies.

During the winter, the bottom temp should stay near 39°F. If the diffuser disk is placed properly, that temp shouldn't change.

Are you saying as a rule of thumb the bottom of the pond will be at, or around, 39°F through cold months, or with aeration it should be at 39°F through cold months? It was my understanding that the bottom of my pond would hoover around 50-55°F year round (without any type of aeration/siphon pulling cold water off the bottom)?

My system is rated at max. efficiency with the following incoming water temps:
50°F/heating
59°F/cooling

Given the fact that my pond is mostly spring fed, there would not be enough "flow thru" to change bottom temps that drastically with a bottom siphon type spillway. However, I like the idea of removing water from the bottom as opposed to letting it flow off the top (current state).

We put in a geothermal system several years ago. We had looked at using the pond, but the contractors we talked with all talked us out of it. We went with two 300-foot deep closed-loop wells that stay very close to 53 degrees. As ESSHUP says, the bottom of the pond will generally go down to about 39 degrees when the pond ices over.

So we're saying that generally the bottom of a pond in a northern climate, non-areated, will hoover around 39°F?

The geothermal story goes something like this:

We knew we wanted to use geothermal as our primary heat/central air. Geothermal company said if we had room for a pond to definitely go this route. We knew we wanted a pond on the site and had plenty of room, so this seemed like a no brainer. Turns out, after receiving our tax rebate this year, we actually got paid to put in our pond.

Unfortunately I did not come across this site until the above was all said and done. Now the task is trying to introduce as much oxygen as possible to create a well balanced "pecosystem" without over mixing and screwing up things with the geothermal system. (This is where I think the cold water spillway/siphon could play a role)

Yes. Water is densest (i.e. heaviest) at 39°F. So, in the winter, the deepest water in the pond will be hovering around that temp. It may be a bit higher, but not lower, and if you pond ices over, it won't be in the high 40's or low 50's. The warmer the water, the lighter it is. When it gets to the surface in cold weather, it cools down, gets denser and sinks. That happens until it freezes over. I have seen water in the low 40's in my pond when it was iced over without aeration right below the ice. It was colder than that at at the bottom of the pond - only 2 degrees, but colder.

With a bottom diffuser aeration system, typically you want the diffuser on the bottom in the deepest part of the pond for the summer, and about 1/4-1/3 the total pond depth for the winter. I'll bet that you could put a diffuser up off the bottom during the summer (maybe half the total pond depth) and keep the water down there cold for your cooling needs, but still keep the O2 levels in the upper portion of the water column higher than without an aeration system. That's a SWAG, as I don't know the layout of your pond.\

Or, an agitator with a short tube would work in the summer too.

Correct me if I'm wrong, but frozen pipes burst because the expansion is constrained. With a siphon system, you're not constrained (unless you have valves closed on the inlet and outlet), so the pipes can freeze with bursting them.

Hogfan, yes limited room for expansion is what would take most pipes to failure. And, in an open system, there should be nothing to constrain the expansion. However you must remember that water freezes from the top down. Put water in a glass (open system) and if allowed to freeze the glass will break because the top freezes first, closing the system.