How long to collect

Just got a refractometer so the first time I’ve checked the level of my runnings while sparging and I have 12 gallons and still pulling 7 on the brix scale with temp compensation so how long do you continue to sparge
Thanks randy

Sparge until you have your target amount of preboil wort.

Maybe you might want to sparge more slowly so you set up a better gradient and push the sugar-rich wort down without mixing it so much with the water above.