Drain smell.

Don't forget to check your tank vents. Having sat for a year, critters could have decided that the vent pipe made a good nesting hole. Air has to go somewhere when water displaces it. The AAV is also a good bet to have gone bad.

Lyle

Moved from Forum Technical Support

I've read that the black tanks should be closed and only open/empty when 3/4 full but is that true for the grey too?

Yes. At least that is what we do. But then again, we very seldom camp in places where they have full hook-ups.

As GMandJM said, "Personal preference and to each their own."

We leave our tanks closed and dump them when needed. I don't like "sewer flies". Supposedly keeping a bend in your sewer hose works as a P-trap. Personal preference and to each their own.

Anyways....

It could just be that your sink drains/p-traps need a good cleaning. If the rig has been sitting a year, the "stuff" down there might have dried onto the piping.

If you're having grey tank odors, you may want to shut the tank then pour some Dawn or Calgon down the drain. Fill the grey tank and let it sit awhile to "de-gunk" the inside of the tank. Dump the tank and see if that helps.

And have you checked your water-heater anode rod, if you have one?

Leave the grey open. You put a lot more water into the grey tank than you do the black - it's a pain to go open the grey tank valve in the middle of a shower..........

When the black tank is getting to the point you want to drain it, then close the grey valve so it fills with enough water to clean the hose when you drain the black tank. Leave the grey tank open until the next time you need to drain the black tank.

I don't know what is causing your smell.

Bill

We keep our gray tank drain open all the time due to the fact that we use our clothes washer and dish washer a lot and along with showers, the tank will fill quickly (65 gal tank).

You are probably experiencing a bad Air Admittance Valve (AAV) located under your sink. Look for a small (two or three inches) device located on top of the drain piping. It screws off and you can find a replacement at home depot or lowes.

And yes, you are correct about leaving the black tank closed until 2/3rd or 3/4th full. If you know how long it takes to fill the gray, you might want to close its valve so that when the black tank needs draining, you can use the gray water afterwards to flush out the stinky slinky. Otherwise, the hose will still have lots of "stuff" left in it. Not good.

good luck

Ron