Thanks for the quick initial feedback. I was told by the previous owner of the trailer to first open the black valve and let completely drain, then while leaving black valve open, pull open the grey valve which should rush into the black tank to help rinse.Once grey finishes drainng then close both valves.
Does this procedure sound reasonable?
I do that,but don't drain all the gray with the black valve open.Open and drain black,open gray for maybe 20 seconds,close gray valve,after black empty,close black and open gray until empty,close gray,remove hose,install cap.
This is exactly what I do except since my gray tank is bigger than my black tank, I will do this procedure several times but only hold the gray valve open for about 5 - 10 seconds. Watching my water level gauge, I will shift the water from the gray to the black every time the black runs dry and when the gray tank first hits the empty mark on the gauge, I'll close the black (after putting the gray water in the black for the last time) and finish emptying the gray to clean the hose. With a clear connection at the end of the dump valve, you can see just how clean the water is coming out of the black tank. People who dump their black tank once and think that it is "empty" should try this method and see just how many times it takes to actually get everything out of the black tank. You'll be very surprised! And then they understand why their tanks sometimes stink up their rv. Shifting the water from the gray to the black will not cause the black water to go into the gray tank as long as the black tank is empty when you are shifting the water from the gray tank.
Those (like me) who have a macerator, can leave the dump open and it will keep the flow of water running out the hose insuring that it won't go back up into the gray if you leave the gray valve open too long. Those who do not have the macerator, probably should close the dump valve while shifting water from the gray to the black. If you don't have this third gate, you should probably install one.
Hope this helps.
Ron & Sandie
'08 Safari Simba SBD35 CAT C7
Toad: 2011 GMC Terrain SLT2
Tow Bar: Sterling AT
Toad Brakes: Unified U.S. Gear
TPMS: Pressure Pro
Member of: GS, FMCA, Safari Intl, CAT
Here's what I've been doing for the last couple decades, and have had no trouble. (I'll let others judge the propriety...)
Get the "Artificial Inseminator Guy" gloves, the slinky, and connect up. Open the black and let all of it run out. There will be some, um, 'stuff' that goes through after you think it's empty; you have to wait a few extra moments for that.
Open the gray. Pick up the hose so the gray runs back into the black tank, and count to 50. Drop the hose and close the gray. Again, wait for all the last stuff from the black to go through.
Open the gray again. Pick up the hose and count to 50 again. Drop the hose and close the gray again. The black should be really clean this time, so after it's empty, close the valve.
Open the gray again and let the rest of it go. Go inside and put the half cap of cheap laundry detergent and the heavy squirt of dishwasher soap in the stool, fill the bowl and empty. Inside is now ready to go.
By this time the gray tank is almost finished draining. Watch for the last bit of it, then close the gray, make sure the hose is clear, then put the hose away. Running gray water through the hose like this cleans it nicely, so there's no leftover nastiness to deal with.
Ready for the road. I'm typically done in less time than it takes most folks to dump.
I pull the gray tank first for a few seconds to test the drain connections. If there is an issue, cleanup would be much easier. Then I pull the black. After draining, rinsing and closing the black, I pull both gray tanks.
1999 F250 XLT Superduty Supercab 2WD, V10 pulling a 2006 Keystone Cougar 243 RKS
Oh yeah, the wife & Beagle come along too!