Here is a simple winter test for those of you protecting palms in mini/makeshift "green houses" next winter....At the beginning of a major cold spell, get some dry ice and a large bowl of boiling hot water. Place the bowl of boiling water inside the greenhouse and then put the dry ice in the bowl and seal up the green house. The effect of the carbon dioxide gas released will make the plants naturally cold hardier by stopping the process known as evapotranspiration. As quoted from an article which can explain it better than I ever could.... "Plants give off water through tiny pores in their leaves, a process called evapotranspiration that cools the plant, just as perspiration cools our bodies. On a hot day, a tree can release tens of gallons of water into the air, acting as a natural air conditioner for its surroundings. The plants absorb carbon dioxide for photosynthesis through the same pores (called stomata). But when carbon dioxide levels are high, the leaf pores shrink. This causes less water to be released, diminishing the tree's cooling power. The warming effects of carbon dioxide as a greenhouse gas have been known for a long time, says Caldeira. But he and fellow Carnegie scientist Long Cao were concerned that it is not as widely recognized that carbon dioxide also warms our planet by its direct effects on plants. Previous work by Carnegie's Chris Field and Joe Berry had indicated that the effects were important. "There is no longer any doubt that carbon dioxide decreases evaporative cooling by plants and that this decreased cooling adds to global warming," says Cao. "This effect would cause significant warming even if carbon dioxide were not a greenhouse gas."" DISCLAIMER: I never tried the Dry Ice Experiment. It just makes sense based on existing science and data derived from the global warming effects of carbon dioxide and its effects on plants. As for Global warming of the planet...I have no opinion on that and feel that there are too many factors to be considered beyond rising carbon dioxide levels to be sure of anything. This post was edited by Kokomo-JB on Mon, Mar 18, 13 at 9:29

2 or more different spots under truck? or same relative drip point but drips in different places depending on where you park?

Antifreeze lowers the heat capacity of the system. If the design accounted for this use a mix required for the temperature you will see. Non-toxic is required if you do not have the required isolation from the potable water supply (almost all system). A pressure reducing valve is not enough isolation. If the valve malfunctions the potable supply can be contaminated by the low pressure side.

I'm not positive about the antifreeze. It may have a lifespan and you could find that out on Google. However, an expansion tank can last 100 years or 100 days. To check the small diaphragm tanks, the system pressure is reduced to zero. A bicycle valve is then placed on the valve on the bottom of the tank. It should read about 13 pounds. If not, add air. If the diaphragm is broken, there will be water in the tank beneath the diaphragm and it will slosh around. If your relief valve is blowing off, you could have a leaking pressure reducing valve, a bad expansion tank, or a pinhole in a domestic water coil. Ususually a pinhole in the coil or leaking pressure reducing valve will cause the pressure to rise and blow off, even when the boiler is cold. You should be able to isolate both of these and see if the pressure stops climbing. Isolate your cold water supply to the coil and boiler and let it sit overnight. If it blows off, it's one of those two things. A bad expansion tank is usually associated with the boiler blowing off upon a rise in temperature. The pressure and temperature rise proportionately.