"The returning fluid from the "evaporator coils" in my house is about 45 degrees during a defrost cycle..." There better not be any "fluid" being returned from the evaporator during defrost. The system is in cooling mode, so the gas from the inside coil (acting as an evaporator) is going to be cool. It is the compression of this gas (and the heating during compression) that forces the outside condenser to heat up for defrosting. The heat from the hot high pressure gas is then lost to the condenser as the gas cools and condenses to liquid (and melts any frost present on the now heated condenser coil). If the defrost cycle is driven by a simpler timer, the condenser may get rather hot, especially if there is not much frost present on the coil. 'Demand' defrost systems should help limit unnecessary defrost cycles that simpler timer systems can initiate. The more complicated system (of course) costs more, requires additional components in the system, and thus decreases reliability.

As Busdriver has already pointed out, CPVC may not be used for Drain, Waste & Vent systems. Even if they could get the CPVC pipe in the proper sizes, there are no DWV rated CPVC fittings and the codes prohibit glueing dissimilar pipe and fittings together. When plastic pipe is desired for the DWV system the choices are ABS pipe or Sched. 40 PVC (Some local jurisdictions will permit sched 30 PVC). "But what exactly is CPVC? To answer your question, CPVC is Chlorinated Poly-vinyl Chloride. You can think of this in terms of a second generation of PVC pipe inwhich the chemical formula of the pipe was altered slightly to overcome some of the problems that were associated to PVC pipe. CPVC pipe is made in two dimension standards: Although very seldom used, CPVC and fittings are available in the ASTM Pipe Schedule dimension standard, which means the pipe and fittings are exactly the same dimensions as thier PVC counterpart. The CPVC most often used for residential plumbing systems is made to the ASTM "CTS" (Copper tubing Standard) and the physical dimensions of the material is the same as copper pipe. Like everything else in this world CPVC has its good points and bad. ON THE GOOD SIDE: -CPVC is relatively inexpensive when compared to copper or PEX. -CPVC is very user friendly for DIY repair and maintenace because it can be cut with a PVC snap cutter, hack saw, wood saw or a common piece of Nylon Masons twine when used as a wire saw. -Joints are made using a simple primer and glue procedure that requires no specialized tools or training. -Pipe and fittings are readily available in all hardware or home supply centers. -PVC is impervious to the acids occassionally present in the water in some regions that might deteriorate copper pipe or fittings. -Initial installation costs are usually much lower because the material cost is much less and it is not nearly as labor intensive as running copper. -Under most plumbing codes CPVC is listed as approved for both supply (line from the municipal main or well source to the structure) and Distribution (Piping within the structure) and may be used both above and below grade without any additional wrapping, coatings or special protection. ON THE DOWN SIDE: -When compared to the alternatives (Galvanized iron pipe, Copper pipe & PEX) CPVC is the least durable and would have the shortest expected lifespan under normal circumstances. Having said that, it must be understood that while it may have the shortest life expectancy in the real world it would still provide 25 to 30years or more of service without major problems and in regions that have acidic water that would deteriate copper pipe and fittings CPVC would be a much better choice. (I realize that many will argue PEX is a better choice in areas with acidic water but in truth PEX systems all have copper stub outs and fittings that are subject to the same deteriation as copper pipe.) -CPVC has a very high linear thermal expansion factor and when installing CPVC provisions must be made to allow for pipe movement under normal use. -Of all the alternatives CPVC would offer the least resistance to damage resulting from pipes freezing. -CPVC must be protected from direct sunlight or UV exposure. -As it ages CPVC will become slightly brittle and must be protected from physical shock or damage. -When burned, such as in a house fire, CPVC emits a deadly toxic fume. -For reasons known only to rodents CPVC is highly subject to damage from rats, mice, squirrels and Opossums and may not be a good choice of materials for running under a structure with a crawl space or raised foundation, especially in rural areas.

The coefficient of expansion is different for each size of pipe, but for illustration let us consider 3/4" CPVC. For 3/4" CPVC the expansion is 1" per 100' of pipe for every 1degF of temperature change. Assuming the pipe begins at an ambient temp of 70 degress when you start your shower and the hot water is set for the code max of 125 degF the temperature differential in the pipe would be 125-70 = 55degF. The thermal expansion would then be 55" per 100ft of pipe. We rarely see a run of pipe longer than 50' in a residential system, but even at 50ft the thermal expansion would be 27.5". The CPVC installation handbook suggests a 18" expansion loop at every 30' on a straight run and the loop should be located near the center of the run. To make the expansion loop the pipe is cut and a 90deg elbow is installed. The line is then stubbed out 18" and a 90deg elbow is installed. A short 4 to 6" length of tubing to another 90deg elbow turning back towards the original pipe and then connect the loop to the original pipe with another 90deg elbow. On the ends where the pipe drops down through holes the pipe should be run about 18" to one side of the hole with an 18" offset from the pipe to the hole. IN this manner as the pipe expands the 18" horizontal offsets can flex slightly to absorb the expansion. Insulating the pipe will not prevent the expansion because the temperature differential results from the temp of the liquid in the pipe, however if the pipe is first insulated, then pipe hangers large enough to fit the exterior of the pipe insulation are installed, the pipe is free to move slightly within the insulation. If you have your water lines run through the attic space you definitely want the cold water lines insulated, otherwise as the pipe cools from the cold water moisture will condensate on the pipe and drip down on your ceiling causing water damage the same as a leak.

lp thanks for that explanation on the solvent and "glued" joints - i never knew that. I feel better about my plumbing now. I decided to do come calculations to see if I could come up with the 290 gallon number that my HVAC company gave me. I checked my notes from 5 years ago - Does this seem reasonable: Each slinky loop segment was 3' in diameter and was 115' long. That would mean that there were ~38 individial circles each with a length of 2*pi*r = 4.7 feet = 178 feet. Then I had to add another 115' for the return back to the manifold outside (they used parallel loops) so that would give me a total streched length of 293 feet. I have 12 slinkly loop segments so that woul dmean there would be 3516 feet of HDPE pipe in the ground. I believe the pipe was 1 1/4, and that has an ID of 1.157 inches. That would hold 192 gallons of fluid. Then I have 2" HDPE that runs between the house and the loop field. I guessed that it is a round trip of 200' which gives me another 22 gallons. And then I have the inside piping which is 1 1/4 CPVC. I estimated about 300' total which would hold another 23 gallons. Added all up, I come up with 237 gallons. I know that isn't 290 gallons but it is in the ballpark. My loop lengths are estimates - the people who put the system in knew exactly how much pipe was used. So I think the 290 gallon number that my HVAC company gave me is probably right. I remember vividly that there was 30 gallons of anit-freeze put in becasue I had an issue with the gylcol they first used - it was gooing up due to extremely cold temps that year (0 degrees for about 10 days). They replaced the gycol with methanol. So a 30 gallon methanol + 260 gallon water mix would give me an 11% anti-freeze solution and I think that translates into a freeze point of ~20 degree F. That would give me ~15 deg of freeze protection which I think is OK. Hopefully these numbers add up.