Originally Posted by P-J
The warning says:
"10 psi max pressure - DO NOT RESTRICT ON THE OUTPUT SIDE OR YOU WILL POP THE TUBING"
That is for the tubing not the pump. The tubing will have normal pressure in it from the kettle to the pump. The valve on the pump output can be shut off and it doesn't change the pressure in the input tubing.
Edit: Catt22 - I type very slowly.
FYI - 10psi is about 20 feet of head. Imagine a column of water 20 feet tall. that's what it would take to produce that pressure. If your system has the valve mounted on the outlet of the pump itself, then there is absolutely no risk here. Hammy, restricting the flow by the kettle valve is only going to cause more cavitation in the boiling wort. The solution here is to open the kettle valve all the way, and throttle the output on the pump. I also have this problem because my piping is all 1/2", but my pickup tube is 3/8". After you have gotten the wort below about 190F there ought not be any more cavitation, and you can open the valve more. I don't usually end up with it open all the way because it sucks the hops onto the screen, and it gets clogged. YMMV.