Holding Tank capacities

[Eric Perplies]

If you want to calculate the volume of your gray and black tank one
way to do it is:

Bring a hose into your shower. It is nice to have a shut off valve at
the end of the hose. Let the water flow. A modest stream is best.
Leave your gray tank open to drain.

Time exactly the time it takes to fill a five gallon bucket. Be
exact. You can now calculate the flow rate in gallons per minute or
seconds. (Dump the five gallon bucket in the shower.) Do not shut
off the water on the hose or change the flow rate.

Now close your gray tank valve. Note the time. Go back to the shower
room. As soon as you see the water in the shower floor start to back
up, note the time and shut off the water.

You now know the flow rate out of the hose in gallons per minute and
the number of minutes it took to fill your gray tank. Multiply these
two numbers and you will get the volume of your gray tank.

You can do the same calculations with your black tank but it's hard to
do it without getting some water on the floor of your bathroom. I
used two five gallon buckets. One to start the flow of water, once
steady I moved the hose to the second bucket that I timed how long it
took to fill the five gallon bucket. Then switched back to the first
bucket. You then time how long it takes to fill the black tank,
multiply the result by the flow rate and you have the volume of your
black tank.