Do you have it set up basically like this (but without the heater)?:

How high up is the pump pusing water back into the tank?

Where is the pump getting fed its water (from the tank or from a sump at the same level)?

If you can give us a little more about the actual plumbing lines we may be able to figure out what is going on.

Here is the flow chart for the QO 4000.  If you figure out the head pressure that might help also determine what your flow rate should be:

________________________________________________

Keith

"Simply put, you believe that things or people make you unhappy, but this is not accurate. You make yourself unhappy." Wayne Dyer

My Setup is exactly like that (yes excluding the heater).

From the end of the VU sterilizer to the top of the tank is 3.5 feet

Water is coming from the tank, not a sump (using Rainbow CustomFlo Kit)

The setup is as follows:
Intake and Exhaust in the tank using the CustomFlo kit.
7/8 Line is used all around.
Shutoff valves are Intake 1" Ball Valve, Exhaust 3/4" Ball Valve.

So the intake goes from 7/8 house to a 1" ball valve, to the 4000 pump.
Out from the pump to the AF-94-19, then AF-93-19, then QL-25.
Out from the QL-25 to a 3/4" ball valve, to a 7/8" hose to the tank.

I have this setup for just over a month.. I have emailed Pentair
about both issues (pump pressude and UV Bulb),And they have not replied.
I would hope, that after spending big bucks for this setup,they will replace the bulb.

Also the CustomFlo probably is doing a little restricting also as it accepts 1/2" or 3/4" tubing.  Did you cut off the 1/2" part of the customflo so just the 3/4" is there?  If not that may help some.

I am guessing that you probably have a total of around 6-8 feet (maybe more) of head pressure from just the plumbing.  3.5' of tubing, at least two 90 degree bends in the Customflo (each 90 adds one foot of head pressure) and then the 3/4" ball valve.

At 8 feet of head pressure you will be getting about 400 gph.  Depending on what attachement you are using in the tank from the customflo it may not be a whole bunch of flow (especially if you are using more than one output).

Hopefully Pentair replies (or you may consider calling them).  If you can take a picture or two of the set up and post them here I certainly am willing to see if I notice anything.

HTH,

________________________________________________

Keith

"Simply put, you believe that things or people make you unhappy, but this is not accurate. You make yourself unhappy." Wayne Dyer

First thing I would suggest is replumbing the pumps inlet and outlet.  Take a look at this picture (http://www.pentairaquatics.com/products/detail/quiet_one/Q1_images/ModSys%2BQ1sm.jpg).  If you can go straight from the pump into the inlet of the filter I think that would be a better option.  You should be able to thread this bushing onto the pump and glue it into the inlet of the filter (or it may have already been included with the filter system). The less fittings/adapters, etc... the better when plumbing.

On the inlet side I would try to avoid as many of the 90 degree elbows as possible.  If you can go straight into the ball valve that would be much better instead of elbowing into the ball valve and then a second elbow into the pump.  The elbows will cause restrictions going into the pump reducing flow.

Even though they aren't pressurized, I would still recommend hose clamping the inlet side also (just in case).

It seems Pentair recommends the 4000HH pump for their modular systems.  While they don't come right out and say that, the descriptions for the HH pump says "Model 4000 High Head rotates and fits into the Lifegard Module filter system." where this was not listed for the other pumps.  But I may be reading into that more than what they are saying.

Hopefully Pentair returns your email so we can get their input on this.  Let us know what they say.

________________________________________________

Keith

"Simply put, you believe that things or people make you unhappy, but this is not accurate. You make yourself unhappy." Wayne Dyer

I know the picture I sent doesn't show the plumbing that well at all..
But I actually do have the pump got directly into the filter, it just has a
a 1 1/4 slip to 3/4 FPT (that is the piece that came with the filters).
But that is already glued in place..

The tape you see is an experiment.. I taped 3 magents to the outside of
the hose.. The people at ECO-Aqualizer (http://www.ecoaqualizer.com/aquarium-x.htm)
put Rare Earth Magnets in the tube and claim that it breaks apart the Ammonia, Nitrites,
and Nitrates from the H2O Molecule. And you don't need to change the water for a very long time... :o)

I do have another valve (ball valve), I forgot about, it is open 100% to the tank right now.
On other days, I close it 10% (90% open), to send water to the Fluidized Bed Filter
(Lifegard FB300).. If I had more pressure I would leave it at the postion all the time..

But the pump makes a weird sound.. Kind of like something is
loose... Or like a big air pocket is in the pump.. But I know there isn't one..