sewer valves

mlts22 wrote:
Same. I used to leave my gray water valve open, but I use a twist on third valve so I can use gray water to back-flush the black tank when dumping.

I do the same. Once the black tank is empty, I close the 3rd valve (at the bottom of the "Y"), open the gray tank valve and let the water level stabilize in both tanks...then close the gray, and open the 3rd valve to let the black drain again. I do this at least twice and it keeps the black tank empty of all solids and tp.

As an added feature, I will also keep the black tank spray running all during this process.

Ron

Same. I used to leave my gray water valve open, but I use a twist on third valve so I can use gray water to back-flush the black tank (might have the water do something) when dumping.

There is also the fact that flies and rodents can crawl through the hose into the tanks if they are left open.

The reason to leave the valves closed is to prevent a poop pyramid and to keep the sludge from the gray tank migrating into the valve seal cavity in the valve. THAT is the number one reason people will have inadequate gray valve and black valve sealing tight. It does NOT take that long to open the valves and dump the tanks. Doug

Leaving the Black valve open will construct you an excellent poop pyramid as the solids will just build up. Always leave it closed until ready to dump the black tank. I used to leave my gray valve open until I read a post on this forum about a member that had his valves open and there was a sewer back up in the campground. The sewage backed up into his trailer and flooded it with raw sewage. Best advice now is to leave both closed until dumping.

Agree with Black tank closed. You can leave the grey open until, let's say, the day before you leave, so you can shower freely, wash clothes, etc, than capture a tank of grey to rinse after the black is dumped.

I would leave all valves closed while gone.

Thank you for the info .

Ron.

Might also want to leave them closed for another reason........

There was a recent thread about a gal in FL that left her hose and tank valve open. The campground sewer system backed up and flooded the trailer with sewage. The TT was a total loss.

Unless you are bypassing the rv's holding tanks you do NOT want to ever leave them open. Tanks should always remain closed until at least 2/3 full, then dump. Leaving the valves open will allow all the liquids to drain leaving solids behind. You'll end up with the dreaded poo pyramid. Since flush systems on Rv's are not pressurized but rely on gravity, you need as much volume and water when you dump to produce force to flush the tanks empty.