LP leaking when I turn on valve...

Thank you all... I am brand new..just bought it at end of last season... And know these are dumb questions but I feel better asking than making a major mistake and putting grandkids in harms way...
Thanks again.

What's happening is that the nut under the handle that the stem goes thru is loose. Take a wrench and give it a little tweek and tighten slightly. This will reseat the "O" ring that's under the nut on the stem for the handle.

JimM68 wrote:
as said above...

These valves will seal when fully closed and fully open, they are not made to operate "in between"

This is true of a lot of plumbing

Except hot water and steam valves. These should not be back-seated because they will expand and jam. Gas valves are designed to seal when back-seated.

as said above...

These valves will seal when fully closed and fully open, they are not made to operate "in between"

This is true of a lot of plumbing

YES tank will need to be emptied when changing out valve.

Valve has a double seat.....one that seals when valve is closed and one that seals when valve is fully opened (back-seated).
Leak prevention when opening/closing valve is done via packing inside valve stem gland and a packing nut.

Unlike a typical valve where packing gland nut can be tightened using a regular wrench most propane service valve packing gland nuts are internal style with recessed slots and require a 'spanner' type adjustment tool (bulk dealer/repair) or replacement of service valve.

Jackutah wrote:
My tank is full...do I have to empty it to replace the valve?

LPG dealer will take care of that when they replace the valve,

My tank is full...do I have to empty it to replace the valve?

Spray some dish washing liquid and water. on knob, and fitting and gas line.

look for the bubbles..

willing to bet your gas line is dry rot..i have replace mine twice.
Its a DIY project. Teflon tape and wrench

If the leak stops when the valve is fully opened, you can either live with the brief leakage or have a tech repair/replace the valve. If the leak does not stop when the valve is fully opened, then repair/replacement is your only option.