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Thread: Auto drain valve

  1. #1
    DIY Senior Member rockycmt's Avatar
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    Nov 2007
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    New York
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    Default Auto drain valve

    While rebuilding my system I noticed they had installed auto drain valves at the lowest point. Since I had the line dug up I decided to remove it incase it was faulty since it was old. How do these things work? Do they sense low pressure and open? Are these reliable? If I do not reinstall it will I be ok with just blowing my lines with air before the winter?

  2. #2
    In the Trades Gary Swart's Avatar
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    Sep 2004
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    Interesting question! I installed my sprinkler system in 1985 and, following directions of the designer, I installed several automatic drains. It wasn't until that fall that it occurred to me that I had no way of know if they were working. Now, I had socked the lines 2 feet deep, but sometimes it does get cold enough to freeze that deep, so I started having my system blown out. I do it myself now, but I still don't know if the automatics are working or not. Since I have my own air compressor, blowing the lines is not a big deal or expense, but if I had to hire it done it would probably cost $50 or more every year. Guess my compressor has paid it way pretty well.

  3. #3
    Plumber jimbo's Avatar
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    Aug 2004
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    Auto drain valves are "normally open" to atmosphere. When pressure is applied in the system, they close to allow the system to operate, and are spring loaded back to "open" when pressure is removed.

    On the submarine, we had to know where all the auto drain valves for main ballast tank blow system were. They were located very low in the boat...usually right near deck plate level in the lowest level. They made sure that no condenstation was allowed to accumulate in the line, but had to close in a hurry when the 4500 PSI air hit them. You had to observe the valves on a regular...hourly....basis, because they acted as a "tattle tale" in case the MBT blow hull stops leaked by...( water in the people tank...not good!)

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