Just got our 42v13 a couple of weeks ago so this is the first time I've drained our GW tanks. Tank 2 drained fine. When I pulled the lever for tank 1 a little water drained out, then nothing. Tank 1 still reads 2/3 full. (Tank 2 reads empty now.) Could it be clogged? If so, can I use regular household declogger (e.g., draino)? Any other troubleshooting tips?