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Posted by HeatPro on July 24, 2007 at 22:19:09:
In Reply to: back flow valve posted by nmbonomo on July 24, 2007 at 16:33:22:
OK - fess up. Who put toxic chemicals inside the boiler. It must have been the person who advised you to get rid of the toxic chemicals, as plumbers usually follow the written Weil-McLain directions that come in the box with the boiler to put only potable water or non-toxic propylene glycol into the boiler water so they don't void the warrantee.
Also, considering that the maximum boiler water pressure of the relief valve is 30 psig, so the boiler rarely gets to 25 psig (your pressure relief valve doesn't pop regularly dumping water on the floor does it? - and if it did, would there be toxic chemicals left after doing so?) So if the city water pressure is more often over 40 psig, and the pressure inside the boiler never gets over 25 psig, how does the boiler water get out to the city water line? Is there some magic that makes boiler water go upstream?
At any rate, some day, there might be a day where the city water pressure drops below 25 psig, so the water inside the heating system, all 10 gallons of it, might poison the city by mixing with several million gallons of city water.
Thus it is always a good idea to replace a backflow preventer, as it is imperative to continue to remove your shoes when boarding a plane because bad things can happen once in eternity. This will make sure that you and other dangerous people don't go around putting poison inside cast iron or steel vessels like residential boilers.