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Keep "pond water pipes" from freezing

I'm running 1/2 pex tubing under 3 inch PVC Pond water pipes. Some pipes will have pond water flowing, some won't, but the ones that aren't flowing will have pond water sitting in them all winter. I'm doing this to protect them from freezing in the winter when some pipes get shut down, or if the pond pump fails, I won't crack any pipes. The pipes are 2 inch's to 1 foot deep in the ground in Chicago ( -20 degrees at times). I think I will circulate anti freeze 24 hours a day threw the pex and put the sensor of a: http://www.supplyhouse.com/Caleffi-201000-Thermostatic-Control-Head-with-Remote-Sensor-45-82-F on the return antifreeze pipe. This will allow a: http://www.supplyhouse.com/Caleffi-220500A-3-4-NPT-Angled-Thermostatic-Radiator-Valve-Body-3-7-Cv to open and allow heated antifreeze to flow when I set it to 45 degrees and the return water comes back less than 45 degrees. I will turn on the pump when freezing temperatures start in the fall.
Any ideas?, will it work?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 17,123
    And what are the pond water pipes for? A heat pump?

    If you have antifreeze in the heating pipes -- not, perhaps, a bad idea -- then you will want to be very sure that the antifreeze can't get into the pond water. The only really reliable way to do that, 100 percent of the time, is to ensure that the pond water pipes are at a slightly higher pressure than the antifreeze pipes, throughout their length, pumps on or pumps off. Can you do that?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PaulWojnicki
    PaulWojnicki Member Posts: 17
    No Heat Pump. The pond is a backyard garden pond with large Koi fish. A pond water pump is left on during the winter to filter and move water thru some of the PVC pipes. Other pipes are not used, like for the waterfall, however still need to be protected from freezing as it is impossible to drain these pipes. The pex tubing that has the heated antifreeze, is running under the outside of the PVC pipes, in the dirt near the pond, not inside the pond. The pipes travel from the garage to the pond jets, skimmers and bottom intakes. The only way for antifreeze to get into the pond would be if there was a leak in the pex. In that case only the volume of diaphragm expansion tank under pressure could leak out, and it would just go into the dirt.
    So right now I have the ends of 1/2 pex tubing coming into my garage, supply and return. And I have to devise a heating system to keep the 3" PVC pipes from freezing. I have radiant floor heat in the garage with a manifold that I can tap into for a heat source.
  • Jamie Hall
    Jamie Hall Member Posts: 17,123
    Well... the idea should work. A couple of thoughts.

    First, the circulating pipes won't freeze, in general. Or, if they do show signs of freezing -- or your pond shows signs of freezing! -- you should have a pond heater to keep at least a small area of water open. But I presume you knew that.

    Second, any pipes under the pond also won't freeze -- the pond will see to that.

    If, and only if, the pond has a good liner the antifreeze in the pipes would be OK. Antifreeze, however, is quite lethal to fish, and if they are large koi, you really don't want to do that. The odds on the PEX leaking are pretty low, but they aren't zero.

    As I say, it should work, and it is ingenious. But I'd seriously look at ways to either drain the threatened pipes or keep circulation in them...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 15,053
    Are the pex lines under the PVC that will be flowing all winter also? If so you will be heating the pond with those pex to PVC lines, a heat exchanger of sorts.

    Your idea, a clever one using the TRV should work, but I think the system will require a lot of energy if the pond and all the lines are un-insulated.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rick in Alaska
  • PaulWojnicki
    PaulWojnicki Member Posts: 17
    The pond has (2) disks above the lids of the bottom intakes that air from a compressor will blow fine bubbles from. That keeps the water moving slightly so Ice doesn't cover the pond completely.
    I will try to insulate above the lines that are not buried very deep.

    Yes, the 1/2" pex loop pump would be running all the time, so I could buffer cold and warm spots and get a average return temperature for the sensing bulb to react to.

    I've had some experience with 4" under ground PVC for my roof water from 3 down spouts. They go under ground from each downspout and come back up in the grass. The only one that froze shut was the one that was buried only 8" deep. The other 2 never froze solid, they were buried about 16" to 18". They all have to come up in the grass were air temp is or was 14 below zero, worst low we had in recent times. I removed some of these pipes and none were cracked.
    So if I can adjust the water temp. to the lowest setting and flow rate of the injected heat down, I don't think I would be adding a lot of BTU to the ground. It would only need to be in the middle 30's. I'm hoping when I attach the sensing bulb to the pipe it will feel some of the heat of the garage ambient temp. and not be accurate. Sense the lowest setting is 45 degrees. I can insulate the bulb sensor till I find the sweet spot.
    I like this system for simplicity, however would need to keep a eye on it.
    Thanks for the input.
  • hot_rod
    hot_rod Member Posts: 15,053
    Certainly worth a try. Im wondering if you can move enough BTUs through that 1/2 loop to get the job done?

    All of the TRV heads have a freeze protection setting, the snowflake stencil, 43F, I believe. As long as you stay above 32F and not have to add too much heat and $$ to keep it from freezing.

    A freeze-stat connected to an alarm might be a good idea also.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    delta T
  • Zman
    Zman Member Posts: 7,001
    Depending on your layout, you might consider this product. http://heatline.com/retroinstall.shtml?gclid=CL-Akpyooc4CFQ-CaQodm6QCdw
    You just slide it in the pipe and plug it in only if you need it.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    SWEI
  • PaulWojnicki
    PaulWojnicki Member Posts: 17
    As far as enough heat, I think the fact that it runs from the beginning of the season to the end with out shutting down will keep things from getting to cold to respond. I heat a whole garage slab and the garage with three loops to 75 degrees if I want. My pond guy says his pond water gets to 38 degree's with no added heat, just the aerator, to keep ice hole open. So if the water in the pipes is 38 then the load on the pex would almost be satisfied, already, then its just keeping the other pipes with little water from freezing.
  • delta T
    delta T Member Posts: 863
    Will you have any kind of override to trigger the heating system in the garage if the garage zone is not calling but the TRV is wide open and craving BTU's?

    *Probably* won't be an issue, just a thought. If the garage zone is not calling there is not heat available for the anti-pipe-freeze loop, unless I'm missing something. I would imagine that if it is cold enough out to need the antifreeze system, then the garage should call as well, the trick is to make sure the run cycle is long enough to get enough heat out to keep the pond pipes from freezing. In essence the thermostat inside your garage will be deciding when the anti-freeze loop needs heat in extreme conditions, not necessarily the TRV.
    PaulWojnickiSolid_Fuel_Man
  • PaulWojnicki
    PaulWojnicki Member Posts: 17
    I was going to try it this way first to see if its good enough. But if I notice early in the first season that the Temp. is to low at times. I would have to zone it. It would then become a project!
    Also a side note:
    I have (2) detached garages that get there heat from a condensing Weil-McLain Ultra boiler in the house. One garage is older with cast iron baseboard heat, the newer one radiant floor heat. I leave the pump running antifreeze all winter between the heat exchanger in the house and the garages. Heated water circulates thru the other-side of the heat exchanger when there is a call for heat in the house. Right now I don't use a thermostat in either of the garages. Surprisingly it heats very close to what I want it to, about 45 deg. on the coldest days to 60 in mild weather. So pumped antifreeze is available 24-7 to the TRV. So some BTU is available either from the heat stored in the slab, piping or CIB and new BTU's from the house.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,307
    Sounds like a fun project! The garages you describe are envious as well! Just out of curiosity how many there's of gas do you use? Pumped glycol does have some advantages, just keep an eye on the water chemistry.

    SFM
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • PaulWojnicki
    PaulWojnicki Member Posts: 17
    Here is my Natural Gas use history BEFORE this project for a baseline.
    See attachment.
    Presently I'm heating a 2-story house, 2800 sq ft area, finished basement, 5ft below grade, two detached garages. Cubic ft. is more because of cathedral ceiling and 2-story Great Room. All open cell foam insulated, closed cell in basement. I have radiant floor heat in the house, and one garage, 600 sq ft with heated attic. Cast iron baseboard in basement and 480 sq ft garage with heated attic.
    I heat the house to 71 degrees 24-7. The garages bounce around a little because I don't use any t-stats in them, 40 on cold days 60 on mild.
    I use a Weil McLain Ultra 155 for heating everything, and indirect fired water heater.
    My last gas bill was (Summer) $66.74 of $33.51 was a fixed Customer charge. So that would make my domestic use at $33.23 year round, a month, when gas cost was $.2958 per therm. Gas prices have been low for a couple of years now.
    My biggest gas bill was $332.00, used 363 therms on 1/15/14.

    I'm using these products for testing antifreeze and inhibitor levels.

    http://www.supplyhouse.com/Hercules-35271-Cryo-Tek-Anti-Freeze-Test-Kit

    And this inhibitor

    http://www.supplyhouse.com/Hercules-35297-32-Oz-Sludgehammer-Universal-Corrosion-Inhibitor


  • PaulWojnicki
    PaulWojnicki Member Posts: 17
    System has ran 2 winters now. It runs perfectly, the delta-T of the loop protecting the pond pipes is 10-20 degrees, lowest temp is 50 degrees when not much heating going on in the garages. Gas bill went up about 20-$30 per month. I also ended up running pex under a long run of 4" PVC pipe that drains water from my roofs, had to do that because its not buried very deep. Some changes I did last winter was to heat the pond with a stainless steel swimming pool heat exchanger. I ended up needing a higher temp. glycol so I had to zone the garages. I put another TRV on the garage slab that has the pond pumps. The other garage with the radiators is on a zone valve. The pond water T-stat has many options to control temperature but ultimately turns on/off a 110 volt outlet. I put a remote sensor on the shell of the heat exchanger. I plugged in a 24 volt transformer and it will open a zone valve to flow antifreeze into the pool heat exchanger when energized. The end switch closes and the boiler goes to 185 degrees. Heating the pond is big bucks will use in extreme weather only.
    Thanks for the help
  • still_c
    still_c Member Posts: 2
    edited January 23
    Hi everyone, I'm new to all the pond theme, I've been reading through this thread, and got concerned. Is it possible to face such a freezing issue with aerators? I have Aquascape Pro Air 20 in my pond. It is supposed to work well in winter, but who knows, maybe that's just for marketing.
  • PaulWojnicki
    PaulWojnicki Member Posts: 17
    edited January 23
    Hello,
    Running a aerator in the pond is done to keep a area of ice open to exchange gases so fish can survive.
    The other ways are to use a electric floating pond heater, run a small submersible pump, or heat the pond.
    Some people build a plastic enclosure tent "hoop house" over the whole pond.
    Most will do a air pump with a air stone. It is the cheapest way to go. If you have fish in your pond, don't
    put the air stone on the bottom of the pond, should let it hang in the pond about a foot or so deep from the top surface. If you put it on the bottom it will circulate the water from the bottom to the top. The water on the bottom of a pond is the warmest, the fish like and find the warmest area to stay in the winter. So hanging only a foot down will keep the surface open, but won't disturb the fish, also its not good to have water currant's near the fish as they will have to fight to stay still and are trying to preserve there energy to make it through the winter. When it gets very cold outside, like 0 degrees, sometimes the hole will close up, it will reopen when it warms again. I float 1 inch thick 4x8 ft polystyrene insulation sheets on my pond. It holds heat in the pond.
    The fish don't eat below 50-55 degree water temperature and the metabolism slows down.
    They actually lay on the bottom, so sweep the area of stone rocks or pebbles so they don't get marks in the skin.
    As far as the air pump is concerned, I keep mine in my heated garage and run the airlines to the pond.
    It runs 24/7 no problems. Most are designed to be outside, probably best to cover it at least from the elements.
  • Jamie Hall
    Jamie Hall Member Posts: 17,123
    Your query would be MUCH better in its own new thread, @still_c -- since it's a sort of a different topic. However... no, the ProAir aerator you have shouldn't, itself, freeze. Now whether it can keep the pond from getting surface ice on it, or freezing to a depth which will harm any fish, is another question altogether. It will probably just keep right on bubbling, but it is quite possible that the pond will freeze over anyway.

    Depending on how cold it gets in your area, you may want to also have a floating pond heater in there, to keep at least some area open.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    PaulWojnicki