I would say is six of one and half dozen of another. Can't hurt to open them but the only benefit I see is it might save a few minutes since there is less to drain in the Spring. You'll still have to sanitize the entire system either way.
At a minimum, you should open each low point drain just to see if the pink stuff is at the vvesI did open them before, then I closed them and ran antifreeze in.
There's no water in the system at this point, so what would it matter?
I'm thinking it might minimize the residue and make flushing the system next year easier.
This is my first winterization, so I'm sort of experimenting.
Maybe I won't open them.
Unless you have a really big compressor with a very large tank, I would go around opening the faucets one at a time until all the water is gone then close it and move on to the next faucets. Do the low point drains last and one at a time slsoI use the air always, I live where it can freeze and I RV all year. Using the air I can use it and re winterize in a few minutes. Open low points, all air open all faucets & shower, open valve and purge water from toilet water valve. Don't for get the outside shower, if you have a washer dryer consult the manual. Get a fitting and connect the air hose with the PSI set to 25-30.
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I use my small 6 gallon harbor freight the 60 gallon in my shops is too large to haul out. I guess I could park the RV in front of the shop and run a hose. The 6 gallon Looks like this but it's a CP , dial in the lower pressure and it is able to keep up.Unless you have a really big compressor with a very large tank, I would go around opening the faucets one at a time until all the water is gone then close it and move on to the next faucets. Do the low point drains last and one at a time slso