Furnace Plumbing Question

Hello,
Have a forced hot water heating system. Typical 2 story Colonial house.
Have a valve that I have to replace in the main household cold water line.
But, I don't want to mess up the heating system, as the pressure in it is set correctly, etc. There is a valve on its water line, but I am very reluctant to turn it closed, as it hasn't bee used for many years, and I don't want to create a new problem.
Question: If I shut off the main Water Supply Line to the house, would the pressure adj valve going to the furnace keep any backflow from the upper story of the house flowing out when I remove the cold water valve ?
e.g., do these typical pressure valves have a check valve incorporated into them ?
Thanks, B.
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There may be a separate check valve. In any case, if you lose the pressure in the heating sytem, it should repressurize when you turn the water mains back on. I wouldn't get too worried about it.
Christopher A. Young Learn more about Jesus www.lds.org .
Hello,
Have a forced hot water heating system. Typical 2 story Colonial house.
Have a valve that I have to replace in the main household cold water line.
But, I don't want to mess up the heating system, as the pressure in it is set correctly, etc. There is a valve on its water line, but I am very reluctant to turn it closed, as it hasn't bee used for many years, and I don't want to create a new problem.
Question: If I shut off the main Water Supply Line to the house, would the pressure adj valve going to the furnace keep any backflow from the upper story of the house flowing out when I remove the cold water valve ?
e.g., do these typical pressure valves have a check valve incorporated into them ?
Thanks, B.
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On 11/27/2012 7:48 AM, Stormin Mormon wrote:

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Repressurize is not the problem. If the heating system pressure is lost when house drinking water system is drained the OP's drinking water system will be contaminated by the heating system water.
I can't imagine there isn't a check valve somewhere between the boiler and the house water supply. It is a basic principle that water must not be able to flow back into the drinking water supply.
But I would try shutting the supply valve to the hot water heating system. IMHO this should be maintained as a working valve.
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yeah if the heating system ever malfunctions a non functional valve would mean no water in the home at all.....
time to install a new ball valve, they appear to last forever
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