You have to remember that there are over 300 gallons per minute going through each filter and set of pipes. If you suddenly close one valve, then you are stopping all of that water, which will cause a pressure wave to reflect off of the valve and you are forcing it into the other tank. Closing one valve is not as bad as closing both, but it's still bad.
What is the filter pressure now that all of the water is only going through one filter?
I think that the indentation and scratch are close enough to the crack to possibly be related. If it created a defect, the defect could have propagated as the filter was repeatedly pressurized and unpressurized.
What is the filter pressure now that all of the water is only going through one filter?
I think that the indentation and scratch are close enough to the crack to possibly be related. If it created a defect, the defect could have propagated as the filter was repeatedly pressurized and unpressurized.