Today I'm going to talk about the gray water holding tank, that's the tank under the RV that stores the wastewater from your sinks and your shower.
When you're staying at an RV Park with hookups the gray water tanks have very little use. Since their designed as storage tanks and you don't need to store gray water if you have hookups, you would normally just hook up your drain hose, leave the gray water valve open and let the gray water run into the RV Parks sewer system.... This is a little off-topic but never ever leave your black water tank valve open while you're hooked up. I will cover this more when I write about the black water tank and how to deal with it.
It's only when your Boondocking that you have to worry about your gray water and the tanks that hold it. And the only thing you have to worry about is the empty space in them and how much of that you have left. Some RVs will have one gray water tank, and the kitchen and the bathroom gray water will be plumbed into that one tank. Other Rvs like my Arctic Fox, have two gray water tanks, one for the bathroom, and one for the kitchen. And if they're designed properly their sizes will match up fairly close to the amount of freshwater that you have in your freshwater holding tank. Like for instance my Arctic Fox has a 73 gallon freshwater holding tank, and two 35 gallon gray water tanks. And the theory behind this is that the freshwater holding tank will be the limiting factor of how long you can stay boondocked. Since there's a black water holding tank also getting fresh water added to it, normally water will be what you run out of first. Which is the reason why so many boondockers have devised different ways of carrying drinking water to their RV.
Your RV will have a gadget that is supposed to tell you how empty or full all of your tanks are. And this is usually a series of lights that light up as your tanks fill up. My experience has been, and I think most RVers will agree with this, that these gauges are almost totally worthless. There are a variety of reasons for this such as, grease build up, something hung up on the sensors, and these things ARE often the problem. But I think something that's often overlooked is the fact that due to where the tanks have to be placed that there often not very tall. In other words the tank may be 6 feet long, and 3 feet wide, but only 6 inches tall. And because the sensors are measuring how tall the liquid is in the tank, if the tank is only slightly unlevel it can make a huge difference in what your sensors are reading because your sensors may only be 1 inch apart.
Other than dumping it when it's full, the gray water tank requires very little care. Some people complain of smells coming from their gray water tank, but I've never experienced that personally. I'm very careful about what goes into my gray water tanks. I try to keep as many food particles and grease out of my tanks as possible and I do this by wiping my dishes and pots and pans with paper towels before I wash them. I also have a screen over the kitchen drain that filters out smaller particles.
They sell various concoctions that you can put in your gray water tank that is supposed to keep down or prevent any smells but I've never seen the need for any of them and frankly have never seen any evidence that putting chemicals in your gray water tank does anything beneficial. I believe that if you keep as much food and grease out of your gray water tank as possible and make sure all of the P-trap's in the kitchen and bathroom have water in them you will have very few problems with your gray water tanks
Now as for where you dump your gray water tank I'm going to put off talking about that until I write about dealing with your black water tank, because they're both dumped in the same place, at the same time I will cover that thoroughly in my next post about consumables.