Your RV has a three part water system.
(1) A portable fresh water holding tank with a pressure demand 12-volt water pump.
(2) A city water (water hose) connection that provides water to the system which bypasses the fresh water holding tank and the water pump to supply your fresh water.
(3) Waste water holding system designed to capture and hold all waste water.
Portable Water Tank System
The portable water tank system is a relatively simple system. It consists of a plastic holding tank which is filled by either a gravity fill system and/or a pressure fill system, which requires a hose to be connected to a fitting and a valve turned to the fill position. Regardless of how the tank is filled, the tank will be drained by gravity. There will always be a valve to drain your tank. Normally, it will be located by a white plastic petcock style drain. If you are having trouble locating the valve, find the tank itself, which will often be positioned very close to the fill receptacle. The drain will be in one of two locations: (1) under the trailer in the approximated location of the tank itself, or (2) in the compartment where the tank is located. If the tank is above the floor of the RV, 95% of the time the drain will be inside the RV next to the tank. If the tank is below the floor, the drain will be underneath the RV. Always remember to drain your fresh water tanks between each use. This will prevent any stagnation that can cause water to taste and/or smell bad.
TIP: You can sanitize your RV fresh water tank with a small amount of chlorine bleach; 1-tsp for every 40-gallons of water. Running the solution through the entire fresh water system can prevent or reverse the bad taste or odor caused by stagnation. DO NOT mix bleach with ammonia, as this combination can create a toxic/poisonous gas! Always make sure your water system is ammonia free prior to using chlorine bleach for sanitization. Also, remember to flush the bleach solution out completely prior to using the water system.
NOTICE: Water left in the RV’s fresh water tank can smell or taste bad after a week or two. DO NOT be alarmed! Simply run the water through the system until the odor is gone, 6-10 gallons for the hot water and 1-3 gallons for the cold water. If the odor does not go away, simply follow the directions in the “TIP” above.
The second component of the portable fresh water system is the pressure demand 12-volt pump. The water pump supplies pressure and flow to distribute the fresh water from the holding tank. A 12-volt water pump does have an on/off switch! When the faucet is in the “on” position, the pump will draw fresh water out of the tank and create pressure throughout the water system. If the water lines are empty, it will take several minutes for the system to push out the air pockets. To bleed out the air pockets, turn on a hot water faucet until pure water flows. Then shut off the water faucet and the water system should pressurize properly. Once the proper pressure or PSI is reached, the pump will automatically shut off. When the water pressure drops, i.e. you run the faucet or shower, the water pump will automatically turn on to retain the desired pressure. Due to the design of the pressure demand system. The water pressure may surge during use. Unfortunately, there is not much you can do about this. However, some RVs do have the provisions for an additional pressure accumulator tank.
Keep in mind, the water pump can be noisy. The water lines are made of a hard plex plastic and sometimes the vibrations from the water pump can be transferred into the structure of the RV creating a vibrating noise. Generally, the noise does not come from the pump itself, but the water lines. There is no way to completely remove the vibrating noise; however, you can buy a high-end water pump that will create less vibration to reduce the noise.
TIP: never leave the RV unattended with the water pump on for any length of time! If a leak develops, the pump will run until the tank is empty, and in the worst case, into your RV. After the tank is empty, the water pump can continue to run, which will burn out the pump and will need to be replaced.
City Water – Fresh Supply
The city water system is a simple set up. Simply connect a hose to the city connection and turn on the water at the hose source. NOTE: If you suspect the pressure at the source of the water to be high, use a RV pressure regulator to ensure a PSI of 40. The system will automatically pressurize, although you should bleed the system by turning on a hot water faucet until the water runs smoothly and there is no air present. WARNING: High water pressure can damage your water system! Even though you are on city water, stagnation can still occur. If stagnation does occur, run the hot water for 6-7 gallons and 1 gallon of the cold. You can also follow the directions of the shock/sanitize tip above.
Waste Water Holding System
The waste water holding system contains at least two holding tanks and often three. The tanks are generally mounted below the floor level of the RV and covered with an “underbelly” material. The first tank is called the “black” tank or holding tank. This tank will hold the body waste or toilet water only. A few things to know about your black water tanks are: (1) 99% of the time, the black water tank will only hold toilet waste. (2) Black tanks require a waste digester/deodorant. There are many products available on the market. And (3) black tanks require RV toilet paper. RV toilet paper is specifically designed to break down fast. This allows the water to flow out during the dumping process. WARNING: The black tank level indicator is easily effected by debris caught on the electronics. Any piece of toilet paper on a sensor can cause an incorrect reading. This is a common occurrence with RVs, and flushing your black tank regularly can help prevent false readings.
NOTE: Even with proper care, the black tank is not odorless, and if left unattended or undamped, the odor may fill the inside of the RV.
Grey Water Holding Tanks
The grey water holding tank or tanks “2” and “3” are for holding the sink and shower waste water. Please be aware of which sink/shower drain goes to which grey water tank and the capacity if each tank. You will often find that you may have to budget your waste/grey water.
QUICK TIP: Always dump the grey water tanks last (preferably the shower tank). This will help clean the drain after you dump the black water tank.