For anyone NEW to RV's here is a little information about RV plumbing. This is a very basic article, but for people who don't know anything about an RV and are beginners, this would be helpful. I hope it helps you.
The most important to know is that RV's are designed with the idea that you can setup the RV without any hookups for a couple of days and simply ‘camp'. This has several names, such as boondocking or dry camping.
Their electrical system is designed to facilitate dry camping.
So is the plumbing system.
Most every RV has three tanks 1) Black, 2) Gray, and 3) Fresh.
Fresh water tank is for holding fresh water for drinking and other purposes. If you use the fresh water tank it is important that you treat it very carefully for the obvious reason that you'll be drinking from it. Sheri and I have not yet dry camped so we have not used the fresh water tank and always have a hookup to a water source. I'll write more on the fresh water tank care when I actually do it someday. If you use the fresh water tank, there is also a pump that will provide pressure to the water.
Gray water tank is a holding tank for the ‘used water' that is NOT from the toilet. We've noticed that this tank fills very fast. We fill ours so that we can use this tank to flush out the system when we drain the black water tank, but you really can just leave the gray water tank valve open all the time if your RV is connected to a sewer/septic system.
Black water tank is a holding tank for the water that comes from the toilet. This tank you keep the valve closed and only open it to dump in one big ‘flush'. If you don't do that your tank will build up. You need that flushing concept to keep things going. This tank is not designed to do any treatment, it simply holds the refuse until you can connect it to a proper dump station. People do put enzymes and other things into the tank, but everything you do is designed to simply assist in keeping the tank clean (you don't want refuse to build up on your sensors and give a useless reading) and not to treat the refuse. You must use special toilet paper with an RV that is designed to break apart rapidly.
All for now on this very, very basic article.