Hello everyone....I have a gunite pool and first time closing it. I have already blow out all the lines and the main drain but not sure if I should leave the main drain valve open for the winter season. I have the pool installed last year and the pool company did the pool closing for free (part of the new pool package). And I think, but not sure, the pool guy leave the main drain valve open after blowing all the lines. Now I am not sure if I should leave it open or have it closed after reading some forum and internet search and didn't find any info about gunite pool, kind of worry if I do it wrong. I have already added the anti-freeze on the return lines and the skimmer, also not sure if that's enough. Tried to call the company and of course they won't let you talk to a service tech without scheduling service, so no help. Please any feedback will be greatly appreciated and thanks any help in advance.

Welcome to TFP!

Ideally you want to close the main drain valve while it is in the process of being blown out and bubbles are coming up out of the main drain. That will fill the drain pipe with air and greatly reduce the chances of there being problems. How important it is to do that depends on how far North you are. Being further North, with colder winters, makes it more important. Often things will be fine if the main drain is simply ignored, but how safe that is depends on details of how the main drain pipe runs, which are difficult to figure out unless you noticed while the pool was being installed.

Always close the main drain when you are closing the pool. when the ani-freeze is in the system and you have everything closed and tight. the plumbing will stay safe all winter.