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Filling and emptying water tanks at camp


Filling fresh water tank
I have a 40 gallon fresh water tank in my RV.
Assuming normal conditions, how long should it take to fill my fresh water tank?
I tend to shut off the water source too quickly and not completely fill this tank.

Emptying dirty water tanks
I have 40 gallon grey/black water tanks in my RV.
Assuming normal conditions, how long should it take to empty each grey/black water tank?
I seem to always leave some water in these tanks after I empty them.


as the 2 before me stated......  Use simple math.. or keep an eye on the overflow... 

I purchased a water flow meter to watch when flushing my black tank.. I verified the flow to make sure it is CLOSE to actual and error on the lower side to be safe...

Me-Her-the kids
2020 Ford F350 SD 6.7
2020 Redwood 3991RD Garnet


The rate at which your FW tanks fills is completely contingent on the flow rate of the source filling it and the rate at which your tank can accept water. Do you have good flow at the source, does it have a pressure regulator on it? Mine has an overflow, I watch the sensor to tell me when it's full, but on most sensors, full isn't really full. 

As Nick mentioned, emptying your tanks is complete when stuff stops flowing out. A few factors here as well, like the design of your tanks, if you are level etc. And the sensors often are inaccurate. I find that a black and grey flush helps keep the sensors clean and in working order. 


Jeff - 2023 FR Sunseeker 2400B MBS

Nomad II
Nomad II

Here is what I did. I filled a 5 gallon bucket with water from my hose. it took 50 seconds. Simple math determined the rate was 1 gallon every 10 seconds. Knowing that I can fill my water tank with whatever amount of water I choose with a little easy math and the timer function on my phone.

As for draining the tanks, they're empty when the water stops draining out of them; either that or the drain line is stopped up/plugged. Now if you are relying on the gauges to tell you if they are empty or not, the gauges are rarely reliable. The gauge could read half full when in reality the tanks are empty.