Re: [APD] Return hose hole

["S. Hieber" <shieber at yahoo_com>]

With either line, intake or output, it's possible under
some circumstances to have an unintended siphoning of water
from the aquarium. For example if the pump stops on a sump
set-up and there is no check-valve installed on the pump
output line (a check valve is, imo, a better idea than a
hole). On a sump setup with an an overflow, the overflow
will limit the amount that the aquarium water level can
decline due to siphoning through the intake line and hole
in the intake line would not be useful in that situation.
Another example is is if a canister filter springs a leak,
in which case, either line or both could present an
undesirably wet floor. 

Placing a small hole in the line allows air into the line
to break the siphon once the water level in the aquarium
reaches the level of the hole.

On the output side, putting the hole below the waterline
avoids the surface turbulence that would otherwise occur,
the only harm of which would be a slightly accelerated loss
of CO2 if the water is CO2 enriched. 

The smallest hole possible will be adequate in most cases
-- even a 1/32" hole on a smaller than 1/2" inside diameter
line. However, the smaller the hole, the more readily it
can clog as biofilm accumulates over time. Also, the larger
the diameter of the line, the larger the hole needs to be
to ensure that enough air would be sucked in to break the
siphon. If one drills a 1/8" hole, that should work. You
can check by drilling the smallest size hole ans siphoning
into a bucket, then uncovering the hole (live the line so
the hole is just above the water level) and see if the
siphon stops. If it doesn't, then try the next larger drill
bit.

good luck, good fun,
Scott H.

--- Rachel Sandage <rachelsor at gmail_com> wrote:

> Ahh, that makes more sense.
> 
> On 16/08/05, Liz Wilhite <satirica at gmail_com> wrote: 
> > 
> > I'm guessing BIll meant to say hole in the uptake line
> below the water
> > level, to prevent large spills in case of hose or
> filter failure.


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