ADKDave,
So, basically what people are saying, is that your system is normal. Although going that long on the black tank might be unique, with just 2 I can see where that would be possible. The gray tanks on most rigs fill long before the black tanks. Without doing any scientific polling or calculations, I'd say about 3 times as fast, on average. If you're going 10 days on your gray tank, then that would be just about right for the 3:1 average.
Now, if what you're saying is that you used to be able to go longer, then most likely what is happening is that as you get more familiar with the rig, your water conservation practices might be getting a bit sloppier. In other words, you're using more water to wash up, shower, wash the dishes, etc.
Our rig has 75 gallons of freshwater, 60 gallons of gray and 45 gallons of black. With the five of us, we can go 3 days with mild conservation. We can extend it to maybe 4 to 5 days depending upon if we're solely using the motorhome for all meals and bathroom stops and just how strict out conservation measures are. (For instance, if we're out sight-seeing during the day we many not cook as many meals and use the RV bathroom facilities as much.) But usually it's running out of fresh water and filling the gray tank that limits us. The black tank generally does not fill first.
So, I believe your system is normal....except for the fact that you don't have a fresh water tank. Getting that fixed would be one of my highest priorities. Without a fresh water supply you have put a real damper on the ability for an RV to be "self sustaining".
Well, it WAS an interesting topic. :)
~Rick
