Grey water tank query

duckblind123 · July 2016

At the completion of camping this week, we performed the dumping exercise. I connected the hose to the Black water and opened the value. The Black water tank emptied very quickly with a good amount of force. Next, I moved the hose to the Grey water tank and opened the valve. When the Grey water began to empty, it did not have the same force as the Black water. The tank emptied, but just seemed to not have the same force as the Black water. It took longer, but that is also because th Grey water is much larger than the Black water. I am asking about the force of the Grey water coming out being much less than the Black water. Has anyone else experienced this?
Thanks, duckblind123

Nomad · July 2016

Yes, I experience that from time to time. I think the deal is, the blackwater tank is almost right above the drain/valve. The graywater travels down a tube. If my graywater tank is fuller, it seems to make a difference. Many times I empty my freshwater thru the sink and refill with fresh so the graywater tank is fuller. Another factor is T@Bs drain forward whereas most others drain to the rear. Some dump stations are slanted for others - even though very slightly in many cases. One thing I do in those kinds of situations is lay down some lego block levelers to raise the rear of the T@B to get some downward flow forward.

jdargis · July 2016

I believe 2" gray water pipe, compared to the 3" black pipe, makes a huge difference in water flow. The dump fittings are the same.

KyBawpaw · July 2016

Could be it needs more air above it all. I open the sink valves when draining the gray water tank.

Nomad · July 2016

The sink valves aren't inline with the gray water tank - might help if you're draining the fresh water but the water pump might interfere.

KyBawpaw · July 2016

Humm... I think you're right about that PX. That'll save me some steps at the dump. I just did that as part of routine. Mine drains flow fine. (Except for the A/C thing..never see a drop fall but all is dry inside)

Sharon_is_SAM · July 2016

Wasn't there a recent issue with a blocked gray water vent slowing/preventing the gray water tank from emptying? Had something to do with the shower.

ChanW · July 2016

jdargis has it figured right. The gray water drain pipe is 1½"id and the black water drain pipe is 3"id. We could do the math on it, but I'm too lazy.

Maybe Ratkity can explain the flow rate... B-)

Ratkity · July 2016

Dangit Jim, I'm a microbiologist, not a physicist! *Star Trek ref*

Nomad · July 2016

Well dangit Ratkity - Make something up :-)

Ratkity · July 2016

PXLated said:

Well dangit Ratkity - Make something up :-)

Um... ok..

"The microbes in the gray water tank stick to the sides of the tank and outlet pipes. These microbes obtain a certain symbiotic consciousness and conspire together to create a monster organism that will eventually totally block your gray water flow. This can only be circumvented by sending donations to your T@B University microbiologist who will then expunge the slimey living mass from your pipe for a mere $10k (Bitcoins accepted)"

ericnliz · July 2016

Ratkity,

Good job!

Nomad · July 2016

Excellent :-)

leenscottfl · July 2016

Ratkity that is what I have suspected for some time. Thanks for confirming my suspicions.

JandJ92010 · July 2016

Wow! Who knew that dumping water could be so complicated!

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