Re: [APD] The siphon saga continues...need safety shutoff!

[revance at indiana_edu]

Laura's suggestion of having two siphons, one that wont operate until the 
first fails is possible... you have to put the other siphon above the water 
level in the overflow box. However to keep it above the water level and still 
keep a siphon, you have to put in a standpipe that is filled with water. That 
way the siphon tube is submerged in water on both ends (thus has a siphon), 
but is actually above the "real" water level.  I still don't think I would 
trust it, the water in the standpipe would evaporate, thus would eventually 
lose it's siphon.  I don't think I would recommend this, but I just wanted to 
make sure people understood the concept so they can make their own decision.  
Here is some ascii art to try to illustrate it


   |  |      |  |
   |  |    |~|  |~|
   |  |    | |  | |
   |  |    |      |
   |  |    |      | 
~~~|  |~~~~|      |~~~~~~
   |  |    |      |
           |      |
___________|______|______
      
You can see that the siphon on the left will operate, but the one on the right 
wont. If the one on the left fails, the water will rise until it gets over the 
pipe on the right, thus the siphon on the right will begin to siphon. Again, 
this requires that there is water in the pipe on the right... if it evaporates 
and you lose your siphon... it WONT work.  Hopefully this clears up the idea 
so people can make their own judgements.












Quoting Rod Gerrymander <rgerrymander at yahoo_com>:

> A siphon that can't fail absolutely does need a
> screen, as I found out last night.  That was my
> first response to the problem.  And as you state,
> the larger the surface area of the screen the safer
> you are.  I used a sponge filter sponge, but I know
> it will eventually clog.  I will probably go to a
> more open screen arrangement when I can find one,
> but that will ultimately fail too.  The issue is,
> how long can you expect between failures?
> 
> I don't think the idea of a second siphon really
> helps because I don't think you can have one siphon
> working and then the second one kick in as the first
> one fails.  If both have their ends in the water and
> both are full of water then  both will function,
> relative heights notwithstanding.
> 
> The problem with that is that it reduces the the
> flow thru each siphon by half, which would bring us
> back to my original problem, bubbles in the siphon
> tube.  Of course, if my AquaLifters ever come in I
> may be able to use multiple siphons okay.
> 
> The shutoff is for a final safety check. It's an
> "I'm off to Europe for three weeks and the catsitter
> doesn't know a siphon from an ear of corn" kind of
> situation.  I don't know what will happen, but I do
> know I don't want to pump 100 gallons of water onto
> the floor.  If I ever do that I will have to build a
> shed out back to put my aquarium in.  And sheds are
> against the deed restrictions.
> 
> [An aside, I once told a cat sitter to feed the cat
> a quarter of a can of food a day and she said "I 
> know how to do a half, but how much is a quarter?"
> Think about letting that person even touch an 
> aquarium]
> 
> Thanks,
> Rod
> --- Laura Burbage <leuhrich at yahoo_com> wrote:
> > I was thinking about this problem as I drove to
> > Lowe's
> > and back.  It seems like a shutoff is complicated
> > for
> > this use.  Then I thought of two possible things
> > that
> > could help prevent future water spills:
> > 
> > 1)  Put a screen on that siphon!  Better yet, put a
> > screen around the skimmer box before the inlet.  Or,
> > make a longer piece of the siphon box to extend the
> > inlet, makeing the whole extension out of scren or
> > perforated pipe.  The idea is that if something in
> > the
> > tank comes loose, it will stick to only a portion of
> > the screened area, leaving other areas still
> > working.
> > 
> > 2)  When a system can't be allowed to fail, make a
> > backup.  How about a second siphon, at a water level
> > little above the first, so that it will kick in if
> > the
> > first siphon is disabled.  If used with a skimmer
> > box
> > with a standpipe on the outside part, it shouldn't
> > lose the siphon (unless all the water evaporates out
> > of it)
> > 
> > Hope these ideas are usefull to somebody.
> > 
> > -Laura
> > 
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