Originally Posted by Bdonaldson
When I unplugged the pump the water was draining back down through the Y-check valve and filling the sump. I thought the y-check valve was suppose to prevent water from draining back into the sump.
Sent from my SAMSUNG-SM-N910A using Aquarium Advice mobile app
It is supposed too. Mine does. Whatever water is in the line below the y-check will drain, plus the remaining water in the drains. Maybe your valve is faulty?
Also, is your locline fully submerged? Sometimes that can create a syphon, though the y-check should prevent it. How high id the water in your sump while running? Pics may help me help you.