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solution for the chlorides leaching out of the venting systems
This was inspired by another very long thread. It seems more appropriate to make this a separate thread.
My mod-con has a PVC vent pipe. The installation instructions specifically say the vent pipe should be angled down towards the boiler, so any leaching of chlorides will dump into the boiler.
Now the way the boiler, heat exchanger, etc., are designed, these chlorides will not enter the heat exchanger, but will drain right out the same way the boiler-produced condensate goes, into my mostly-plastic condensate pump.
Now the previous thread is about the suitablility of PVC pipe for venting boilers, especially mod-con boilers, so clearly the way to solve the chloride problem, if it is a problem, is to use stainless steel exhaust pipe instead of PVC.
But I wonder about two things.
1.) In a system such as mine, what is the problem of chlorides in the vent pipe coming back to the boiler, if they go right out the condensate drain without going through the heat exchanger?
2.) Why does the manufacturer say the vent pipe must slope back to the boiler, rather than sloping toward the discharge where the exhaust and "steam" go? Clearly there should be a slope so it does not collect in the pipe and freeze, but why does it matter which way the slope goes?