When you ask in several forums and Facebook groups about the gray tank and black tank there will be a lot of different and sometimes conflicting answers. This led me to write up the way we handle our gray tank and black tank and maybe, just maybe you think this is the way to go!
Just to make it clear, the black tank is waste from your toilet, the gray tank is from your shower(s) and sink(s).
IMPORTANT; Keep both the black tank AND the Gray tank closed! Even when you are having full hookups!
The reason to leave the black tank closed is so that the solids stay in the fluids of the tanks to dissolve and stay soft. If you have the valve open all the time, the fluids will be drained into the sewer and the solids will pile up and create the dreaded “poop pyramid”.
You also want the grey tank closed or sewer flies and other critters can come into your RV and/or odors from the (neighbors) sewer.
Dump when the tanks are 3/4 or totally full (You don’t have to dump both tanks at the same time)
Attach the hose to the dump station hole and if you can find something heavy put it on the elbow so the hose will not “jump” (We use a photographer’s light stand sandbag for it, just look it up on Amazon)
Go over to your RV and hold that end of the hose under your cap while you remove the cap. (Any seeping will get into the hose)
Next, hook up the hose to the RV
Before you pull the handle on the black tank, open the gray tank valve for a few seconds and close it again then check if there are any leaks. When you have a leak and would have pulled the black tank without checking, you make a bigger mess let alone the stink!
When all is good pull the black tank valve open.
Optionally flush the black tank and then close the black tank valve.
Next, open the gray tank valve, this will also flush everything that is left from the black tank out of the hose.
Optionally flush/rinse the sewer hose and close the grey tank valve.
The next task is to add about 3 to 5 gallons of water to the black tank to create a good fluid base again.
Put on latex or other disposable gloves (to avoid any contamination) and get the sewer hose out. Before removing the cap to the holding tank drain opening, ensure both the gray and black water valves are both closed.
Avoid dumping tanks that are not at least 2/3’s full. If you have to dump, add water to the tanks till they become at least 2/3 full. This will help promote all the solids and particles to become suspended in the water and flow out of the tank. If you are going to travel before dumping, you can add some dish-washer detergent (1/4 cup to a tank) and let it slosh around. Caution: Too much soap may cause excessive foaming! (The ice cube trick as promoted on various media does not work, there is a YouTube video that shows that)
Attach the hose to the dump station hole first! It is a good idea to use a clear elbow and a hose ring to connect the sewer hose to the dump station hole, as this will hold the hose in place and avoid any splatter. If the ring or the elbow is not available, insert the end of the sewer hose into the dump station’s hole about eight to twelve inches (if you only insert the hose a few inches the hose may come out when dumping the tanks and that will cause a large mess). Use the hole’s cover, a brick, or something heavy enough to hold the sewer hose in place so it doesn’t pop out of the hole (Do not use an object that is small enough that it could fall into the hole and plug the dump station).
WHERE TO DUMP;
This website can direct you to a dump station: https://www.sanidumps.com/