If a backflow preventer does not have a isolation valve before it, in the event of freezing temperatures should you leave it pressurized or turn off the lower ballvalve and drain it through petcoks? (In texas)

Ive seen people turn off the lower ball valve and drain it. But sense there is still a shot of water in the ball valve below it freezes and burst. Are they better off just leaving it pressurized before heavly Inuslating it and wrapped to keep dry? Ultimately would be best to shut the mainline off at the meter and disassemble the PVB and syphon all the water out. Then turn the lower ballvalve off. But i have some customers who arnt capable of doing that.

•future edit: You can leave it pressurized and just heavily insulate it, leaving the poppet to be the weakest link. But it may not be necessary. While theres no way to eliminate freeze damage. Id still recommend shutting off and draining the pvb. Vs leaving it pressurized. But you don't want to shut it off with water still inside the ball valve. As youre aware, theres like a cylinder inside the ball valve full of water and when you shut it off, it traps the water inside and freezes and breaks the pvb. Its best to Dissasemble and drain water from inside it.

• shut water off to house at the meter

• Dissasemble backflow preventer

• Open petcock ports after disassembling backflow and blow through them (they also trap water inside) and leave them open.

• siphon water from inside all the way past the lower ball valve

• once water is out of the lower ball valve (and atleast a few inches below it)

• turn off lower ball valve

• Turn water back on to house.

• make sure the lower ball valve is water-tight

• Reassemble backflow preventer.

• heavily wrap a blanket around it

• put a trash bag over it to keep blanket dry.

• Run a zone for about 2 minutes (may or may not help get water from the out-bound side of the PVB)

Note: DO NOT turn off the other handle keep it open, febco actually suggest leaving it at a 45° angle.

To siphon; I use a long tube of flex pipe and stick it far down as i can on the inline side. Put my thumb over the top, and pull it out. But It would be better to purchase a hand pump siphon from an auto-parts store. Lmk if you have any questions.