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Sewer Valves – do you leave them open or closed while hooked up?

11-21-SewerValve_smallAnother in the series “The Most Common Questions on RV Forums”

MacWhen you’re on hookups are you supposed to leave the black tank valve open?  How about the gray?  Should they be closed?  When should you dump? …

First a few quick definitions:

  • Black Tank = the waste tank connected to the toilet
  • Gray Tank = the waste tank connected to the sinks
  • Waste Valve = the valve used for dumping the contents of the waste tanks.  Generally there are two, a larger one for the black tank, and a smaller one for the gray

Short answer:  When hooked up always leave the black tank closed until it’s at least 3/4 full and ready to dump.  Generally, leave the gray tank open until a day before dumping the black tank.  At that time close it to allow buildup of gray water for the purpose of flushing out the sewer line after the black tank is dumped.

Long explanation:  The black tank will contain pee (#1) poop (#2) water and toilet paper.  If you don’t use enough water the solids won’t dissolve and will pile up in the middle of the tank.  By using plenty of water, and letting the tank get full before you dump it, it will dump more forcefully and help to get out all of the solids.

  • Always use a full toilet of water for a load of #2.
  • It’s not necessary to add water if you only do #1 just rinse it down.
  • Limit your toilet paper use to just enough to do the job.
  • NEVER dispose of anything in the toilet except the four things listed above (#1, #2, water, and toilet paper)
  • Tell non-rving guests these things and especially ensure that children understand the potty rules

There are two reasons for letting the gray tank build up for a day before dumping it

  • Flushes out food particles and other things that go down the sink and shower
  • Rinses the sewer hose after the black tank is dumped

If you follow these guidelines you will eliminate 90% of your potential sewer problems.

Happy Travels

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