This is an assembly for potable water filter. I need to unscrew this connection but the weights involved and tools I have are making it a pain. I don’t have a large enough vise to hold everything steady. Any tricks I can use to get this apart with a minimum amount of torque?
it’s 1” NPT.
You'll need two pipe wrenches, and the floor.
Place one wrench on the floor with its jaws opening upward. Place one side of the joint to be opened (that is, either the flatted section of the copper or the larger round section of the iron pipe) within the open jaws. The wrench handle should rest on the floor.
Hold the other pipe wrench with its jaws opening downward, and place it over the other side of the joint to be opened. Set up the geometry so that when the upper wrench is pressed down, the joint will unscrew. The handle of this wrench should be on the same side of the work (the two plumbing pieces) as the first wrench, but this handle should be raised perhaps 30˚above the horizontal.
Make sure both wrenches fit tightly on the work. Then apply force to the upper wrench to unscrew the two pieces. You can apply force to the wrench with either your hands or feet.
You may have to take several "bites," one after the other, to fully unscrew the pieces. Because you're working downward, you wil be able to apply more force to the wrenches than you could if working with your hands at waist or table level.
Answering my own question— when you need to supply a large amount of torque and the shape and weight of the items makes it nearly impossible to apply accurate rotational force without twisting/deforming the soft copper, I find spending a bit of money on a bench vise indispensable.
I ran out to the hardware store and got a vise and then used lag screws to attach it to a heavy table top. Helps to pile a bunch more junk on the table.
This table was actually going to go in my office as a workbench in a couple of weeks and I had been planning to attach a vise to it anyway, so I didn’t feel too bad spending the cash on the vise.
I clamped the metal filter head in the vise and used a 1.25” adjustable wrench to turn the copper pipe. With the heavier filter head locked in place, it required a lot less force to turn the pipe.
Moral of the story— having the right tools and equipment makes a huge difference.
