RE: Sump CO2 Help

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

I don't know how much help this will be but here goes.

I recently put a sump on my 150g.  For comparison purposes,
the pump is an external Lifegard Quiet One (rated for
1140gph@ 0' head, over 900 gph against 1', 750gph @ 3',
600gph@ 7', using 1" ID tubing); shut off pressure is 6.5
psi.  I believe the Iwaki MD30 has an even higher psi shut
off pressure.  In my setup, the output is 3/4" ID going to
a PVC manifold that divides into 4 ball-valve-controlled
outlets. The pump must lift the water about 4.5' to the top
of the aquarium, so the maximum available output is
probably around 500gph.

One of these runs through a UV and then a large external
CO2 reactor (3" x 11") using roughly 3/8" ID tubing
(actually Eheim 494 tubing).  One feeds through a small
chiller using 1/2" ID tubing (about the equivalent of Eheim
594 tubing).  A third line (1/2" ID) feeds direct to the
aquarium for additional circulation. The 4th line is a
spare.   

The pump has no problem working all of this and in fact
each line is throttled back with the ball valves.

The sump return line (drain) is a single 1 1/4" line.

If the Iwaki you are considering has anything near the
output of the Quiet One, you should not have any problems
and will probably want to throttle back the output.

With sumps, I think it's generally a good idea to have an
"over-capacity" cettrifugal pump so that you can adjust the
output. The Iwaki WMD/MD 30 series uses a totally enclosed
non-ventilated (TENV) motor so fan noise is not an issue. 
If you move up the 40 series or larger, the motor is
totally enclosed fan-cooled (TEFC)-- so you'll want to
avoid getting an execessviely large pump just to avoid the
extra decibels :-).


The pressure in the CO2 reactor might be much less than you
are anticipating -- only a few psi unless the reactor
output is much more constricted than the imput and you use
a single output line from your pump.

Going in circles:  Note that I originally tried running a
line from the manifold to the chiller and then back to the
sump for redistribution through the manifold to get an idea
of the effectiveness.  I was only running about 100 gph
through the chiller line. Not very effective at all, the
chiller could not cool down the tank -- but the small
chiller is very effectively with the same level of output
running directly to the aquarium.  I bring this up only
because some folks run their CO2 reactor output into the
sump -- that might not be the most effective way to run the
line.   If the sump is covered, CO2 loss would be minimized
and recirculation might be more effective than it is for
chilling.

My sump is covered, but CO2 consumption is about 65% higher
than what it was when running a large canister (an Eheim
2250 modified with a 1060 pump) instead of a sump.  All of
the returns in the aquarium are below the water surface. 
The increased CO2 loss is mostly at the the overflow.  
Interestingly, the increased CO2 rate is relatively
constant even with wide varitations in pump output.  I'm
working on a quantum theory of CO2 loss ;-)

One more point.  Do yourself a favor and connect you pump
with a union coupling on both the input and output sides. 
Imagine needing to dissconnect the pump on either the input
or output side and you'll understand why threaded or slip
couplings are contraindicated here ;-)

Good luck,
Scott H.

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