As mentioned in the past, I joined and put a shutoff valve on the two overflow tubes from my TT fresh water tank. This was done to prevent syphoning of water while driving from the fill station to a campsite.
I did it to prevent the syphoning yet wondered if it would help for dirt, bugs, wasps, etc. from entering the FW tank when it was not in use. I always shut the valve once the tanks were full or if I was not using the TT.
Today I went to fill the tank at home since we are only going 10 miles to the State Park tomorrow and I'd rather not do it as I arrive and found that something had put a plug in the valve.
I filled the tank until water came out the normal overflow spot, near the fill and the spot with the screen. (The overflow tubes do not have a screen) No water came out the overflow tubes until I used a solid #12 wire to probe the valve end and get out the larva that was put into the valve.
Now I'm sure I will keep the valve and suggest that everyone somehow covers their overflow tubes for the same reason.
The valve end was plugged totally.