when you said you insulated the 8" pipe, did spray foam the entire 8" cavity or just your heating pipes. I had read the thread about "insulating pipe failure". Also would the black iron pipes rust or corrode inside during summer shutdown or would i need to us some boiler conditioner? I would think the pipes should be ok since its a closed system. Dennis
You do not insulate the 8" PVC conduit (chase) pipe. You insulate the water carrying pipes within it. Direct earth burial of insulated pipe is not desirable. The insulation properties degrade, some at installation some over time. It's far better to have a conduit in which you put your pipes. Forget about spray foam. It's the wrong product to use. You want "Armacell" pipe insulation. It's sold at HVAC supply houses. It comes in many sizes and wall thicknesses. You buy it in 6-8 ft lengths and slip it on your pipe. It's closed cell insulation so water doesn't get into the insulation and ruin it's insulation properties.
There are lots of bad installation practices that come from the wood furnace (boiler) side of the industry. Don't follow their folly. Do it right and you will only do it once. Do it like an industrial or commercial job.
Again, use a PVC pipe for a conduit. Either the thin wall (commonly called sewer drain pipe) or the thick wall (schedule 40 or the even thicker wall schedule 80). Make sure you find correct the mating elbows, if your installation needs them. Use standard steel pipe insulated with Armacell closed cell insulation. As an alternate the appropriate PEX product can do the job, but my experience has been it's more expensive than steel pipe. Why, because it's not stocked locally and it's a special order and since it's bulky the shipping costs are high. Steel pipe, fittings and HVAC insulation (Armacell) are available locally.
Make sure you do an analysis of the heat flow required to select your pipe size. Don't cheap out and use too small a pipe size.
Generally you do not need water conditioner.
My 2 cents worth plus, enough said.