RV Repair: Sight Gauges for water tanks, holding tanks, water tanks

Question
We recently purchased a 1985 Chateau travel trailer. We are unable to locate any kind of gauges to indicate the level of the gray water tank or the black water tank.  How can we tell when these tanks are full?  

Answer
Betty,
     If there isn't a monitor panel with gauges for the holding tanks then the only way to tell when they are full is when they start backing up in the tub and toilet.  You can buy and add a monitor panel and add sensors to the tanks.  They should be readily available at most any RV parts store.  I hope this helps and good luck.

Darren