Closed Loop Question

I can't figure out why I am getting microbubbles on my closed loop
with a scwd run by a lg 3mqdx...it's about a 1000gph pump.

Here's the schematic:




Output is all 3/4 pvc except for the connections to the scwd which is
tubing.
It is slightly offcentered (i.e. one of the output sides is a little
longer than the other to get around a skimmer.

The input in the tank has a 1 1/2 screen to a 1 1/4 reducer to a elbow
back to a tee which goes up with a cap for repriming. Then down to an
elbow and reduced to 1 inch pipe to the pump.

Unless I throttle it way back I get a lot of microbubbles..even
throttled down 1/3 on output I still get some.

Any ideas on what I could do.

Brian, did you glue everything? Did you use teflon tape on the threads?

Does the intake section have the ability to suck air in at all?

Do the returns have anti-siphon holes drilled? (They shouldn't).

Did you try turning off the pump for 15 seconds, then restart?

Marc


Brian Kramer wrote:

> I can't figure out why I am getting microbubbles on my closed loop
> with a scwd run by a lg 3mqdx...it's about a 1000gph pump.
>
> Here's the schematic:
>
> Output is all 3/4 pvc except for the connections to the scwd which is
> tubing.
> It is slightly offcentered (i.e. one of the output sides is a little
> longer than the other to get around a skimmer.
>
> The input in the tank has a 1 1/2 screen to a 1 1/4 reducer to a elbow
> back to a tee which goes up with a cap for repriming. Then down to an
> elbow and reduced to 1 inch pipe to the pump.
>
> Unless I throttle it way back I get a lot of microbubbles..even
> throttled down 1/3 on output I still get some.
>
> Any ideas on what I could do.

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Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com

Everyting above/out of the water is glued and taped. Some in the
water are not glued and taped to allow adjustments. No anti siphon
holes. I don't think there are any places where it can suck air.
I'll try restarting it. I guess I could silicon the joints as well to
make sure there is no way for air to get in on the intake. I do hear
a gurgle every 5-10 seconds though...but I can't make the intake any
bigger....

Marc Levenson <> wrote in message news:<>...
> Brian, did you glue everything? Did you use teflon tape on the threads?
>
> Does the intake section have the ability to suck air in at all?
>
> Do the returns have anti-siphon holes drilled? (They shouldn't).
>
> Did you try turning off the pump for 15 seconds, then restart?
>
> Marc
>
>
> Brian Kramer wrote:
>
> > I can't figure out why I am getting microbubbles on my closed loop
> > with a scwd run by a lg 3mqdx...it's about a 1000gph pump.
> >
> > Here's the schematic:
> >
> > Output is all 3/4 pvc except for the connections to the scwd which is
> > tubing.
> > It is slightly offcentered (i.e. one of the output sides is a little
> > longer than the other to get around a skimmer.
> >
> > The input in the tank has a 1 1/2 screen to a 1 1/4 reducer to a elbow
> > back to a tee which goes up with a cap for repriming. Then down to an
> > elbow and reduced to 1 inch pipe to the pump.
> >
> > Unless I throttle it way back I get a lot of microbubbles..even
> > throttled down 1/3 on output I still get some.
> >
> > Any ideas on what I could do.

By any chance could your intake basket be siphoning some air (via a tiny whirlpool)?

My closed loop runs silently, but if it does make noise, it is due to cavitation (air
bubbles in the pump's chamber) and I unplug it to allow the air to rise out of the pump. 5
to 10 seconds later I plug it back in and it is silent.

I doubt silicone will really seal PVC. That is more of a bandaid fix, but if you have a
pinhole leak, then maybe that bandaid will do the trick.

Marc


Brian Kramer wrote:

> Everyting above/out of the water is glued and taped. Some in the
> water are not glued and taped to allow adjustments. No anti siphon
> holes. I don't think there are any places where it can suck air.
> I'll try restarting it. I guess I could silicon the joints as well to
> make sure there is no way for air to get in on the intake. I do hear
> a gurgle every 5-10 seconds though...but I can't make the intake any
> bigger....
>
> Marc Levenson <> wrote in message news:<>...
> > Brian, did you glue everything? Did you use teflon tape on the threads?
> >
> > Does the intake section have the ability to suck air in at all?
> >
> > Do the returns have anti-siphon holes drilled? (They shouldn't).
> >
> > Did you try turning off the pump for 15 seconds, then restart?
> >
> > Marc
> >
> >
> > Brian Kramer wrote:
> >
> > > I can't figure out why I am getting microbubbles on my closed loop
> > > with a scwd run by a lg 3mqdx...it's about a 1000gph pump.
> > >
> > > Here's the schematic:
> > >
> > > Output is all 3/4 pvc except for the connections to the scwd which is
> > > tubing.
> > > It is slightly offcentered (i.e. one of the output sides is a little
> > > longer than the other to get around a skimmer.
> > >
> > > The input in the tank has a 1 1/2 screen to a 1 1/4 reducer to a elbow
> > > back to a tee which goes up with a cap for repriming. Then down to an
> > > elbow and reduced to 1 inch pipe to the pump.
> > >
> > > Unless I throttle it way back I get a lot of microbubbles..even
> > > throttled down 1/3 on output I still get some.
> > >
> > > Any ideas on what I could do.

--
Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com