"Lloyd E. Sponenburgh" wrote:

"Tom" wrote in message
...

Perhaps you could supply the make & type of pump and describe the
the the way in which it is plumbed to the tank? What height does
the pump have to draw the oil from the tank?

Also, how do you know that "the pump circulates to the tank at
essentially zero pressure."?

Tom

It's a cheap Prince 11gpm two-stage pump. Cheap. Hooked up to a 1725RPM
2HP pool pump motor. Lovejoy coupling.

The pump is _below_ the fluid level in the reservior. Actually, about 8"
below.

I have a pressure gauge on the HP line, just before the ONLY restrictions in
the bypass circuit -- namely, the OC bypass valve itself.

The return lines are larger than the HP line. The HP line is 1/2", 3-wire,
neoprene coated standard stuff from NAPA.

LLoyd

For someone asking for help, one gets the impression that you're
not amenable to suggestion. Either start from basics or forget it.
If you have a noise problem, the only way is to eliminate potential
causes. That you appear to have an excessively noisy pump can only
be confirmed if you remove any valves and run it straight into the
tank. Noise can be caused by elbows too close to the intake side
of the pump and causing cavitation.
Your problem also can be the result of a poorly assembled hose.
Assume nothing.
I looked at a press a couple of years ago that exhibited just about
identical symtoms to yours. Found that the valve, purportedly, an
open center unit, was set up as a closed center and required the
removal of a blanking plug to act per description. The result was
a noise level about 1/10 of previous.

Tom