Conference unifix::sailing

608.0. "Head Games" by LOONMT::MCWILLIAMS () Thu Jul 30 1987 13:52

    Recently that instrument of marine torture, the infamous MSD (Groco
    type), has found a new way to cause problems. Several times I have been
    getting significant siphoning on the input loop. 
    
    Two years ago, I had the experience of, "Gee, I think I hear water
    dripping, let me get out of bed and see what's the problem ... splash"
    when some toilet tissue had gotten stuck in the Joker valve and the
    head siphoned the Output loop. Since then I installed a vented loop on
    the output, and hadn't had a problem since. 
    
    As I said, now I am having problems with siphoning on the input loop,
    even though I've gone 1.5 seasons without the problem. Installing a
    vented loop on the input wouldn't seem to be a very useful method,
    since the input line is always under-pressured, since that is the way
    the head pump draws water into the bowl (although maybe the the vented
    loop would leak less air into the line than the pump's ability to
    draw).
    
    Analyzing the problem, it looks like the top of the head is very near
    the water line, and the flap valves on the input line are designed to
    open inward (except in the "DRY BOWL" mode, so it looks like it would
    be very easy to set up a siphoning action. 
    
    Does anybody have any ideas about how to go about fixing the problem ?
    
    /jim 

    Not sure how to help other than with nifty vacuum breaker valve
    I found to replace the tiny hole plus rubber disk that frequently
    clogs up.  the product :  SCOT division of ARDOX, Cedarburg, Wisc.
    53012.  The Wilcox-Crittenden replacement model 3100K100 has a 1/8"
    NPT thread.  I bought several at about $8 years ago but don't remember
    where.