Generally, the outlets of the gray waster are 1.5 inches. It would take a great deal of sand to block a 1.5" pipe. The only problem I see would be at the knife valve. If the water is running clear when you close the valve, I see no problem.
Jim & Roy Davis
2016 Hurricane 31S
1961 Rampside in tow
Assuming we're not talking about pounds of sand here, it's probably nothing to worry about. The sand will slosh around and work its way out of the tank within the next few dumps. Hopefully it won't make your dump valve "crunchy" in the meantime.
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