My application:
Man made fish pond with year round waterfall in MN. The waterfall forms nice ice sculptures in the winter but as long as water flows does not freeze entirely. The fish stay happily aerated and there is no need for heaters or bubblers. It doesn't cost any more to run in winter than in summer.
The problem:
How to keep the pond full and pumps from sucking air. The only thing I have read how to do this is bring buckets of water from the house! Of course in the summer people use something similar to a toilet bowl float system. The water line is under ground from the house and shutoff at the pond. Even if you could get the line deep enough (about 46") the float would still freeze at the surface. In practice the water line near the water surface to allow easy shut off and ease of installation. Otherwise you would need to have the water inlet near the bottom of the pond!
My solution (so far):
I use a small 325 gph fountain pump to pump water from the pond into the house and back to the pond creating a loop. Water from the house main is let into the loop via a sprinkler valve and tee. The sprinkler valve is controlled by a float switch and 24 volt AC.
The float switch I am currently using is used for bilge tanks and can be purchased at boat marinas. It works well for low voltage applications just be sure you use water proof wire nuts! It is wired backwards however for my application. It is designed to run a pump to empty water, not fill it! A relay and a home built AC to DC converter (to run the solenoid) solved that problem. (Later I learned that a relay which runs on 24AC can be purchased at Grainger.
The float and pumps resides in a filter box from Aquascapes. Putting the float within the current flow into the filter box prevents it from freezing ... until the ambient temperature gets into the single digits for a few days! Then the surface of the water will freeze as does main water fall. (It forms an ice dome). The solution was to add an outdoor light fixture to the box and then use an Edison based heater (or light bulb would work). A fixed thermostat was also wired in.
Problems continue:
The weak link of this system is power. The whole thing is plugged into a GFI protected 20 amp circuit. The GFI outlet is over sensitive to lightning, etc. and needs replacing every year. It "always" fails mid-winter which results in frozen lines and dead fish! I don't dare take out the GFI protection because it already saved my life once when I when I grabbed the Edison based heater to change it! Having the pumps on a non-GFI circuit helps some but not enough.
Version 2:
My idea is to use a "heated float". Not an expensive tank heater. I'm thinking perhaps an under water light would work. SJE Rhombus makes a Vertical Master http://www.sjerhombus.com/products/product_info.asp?id=370 which could be retrofitted with the lamp instead of float. But I think it is designed for higher current levels than what I would be running. I can't use the "tethered floats" since there is not enough room and also the minimum high/low range is too wide (about four inches). About two inches is the max tolerance, 3/4 inch is ideal.
This system would remove the need for a high voltage heater and hopefully would have more reliable power.
Other ideas?
There are a lot of great ideas on this site but none that have (successfully) dealt with ice. I read of persons using the sun and a mini green house to keep surface water from freezing. This is not 100% however. I only need enough open water to keep the float functioning. I have heard high tech ideas about a water level switch that does not open surface water to work. Like light or pressure sensors. Not sure how to build one or if they would be reliable however. I'm hoping someone here will have experience with a similar application.
Lastly, I would love to have sensors to monitor if water is still flowing and have some recourse if the system fails other than waiting for spring. I think there are flow switches (albeit expensive) and simpler "flow viewers" available but not sure where to get them. Heat wire running the length of the pipe from the house could be used as backup to thaw the line if required. Difficult now the line is already buried however! There do make wire similar to gutter heat wire that could possibly be installed inside the line without digging. It's only 1/2 inch poly however! I have to do something because I can't afford to keep replacing expensive koi! No, I don't want to bring them inside like most people or use un-natural bubblers and tanks heaters.
Thanks for reading and your ideas!
- Chris.
