I am installing a swing check valve on the plumbing of a pond. The purpose is to prevent the water from flowing backwards through the pipes during a power outage. It water were to flow backwards, which I've tested does indeed happen if the pump is unplugged, it would dump dirty water from the filter back into the pond and also potentially overflow the edge of the pond.
I'm wondering if it matters whether the swing check valve is installed horizontally or in a vertical position, if that will have some impact on its function, as perhaps gravity could have some impact on the swinging of the valve.