When setting up your RV at a campsite that has a sewer port included with the hookup amenities, is it better to keep the black tank valve open or closed? 

Leaving the black tank valve open will allow all of the water and other liquids in the holding tank to freely flow into the sewer port. This may sound like a good thing but this has several drawbacks.

Diagram of an RV pyramid plug clog caused by leaving the black water holding tank valve open
Pyramid plug clog caused by leaving the black water holding tank valve open

Without  liquid in the holding tank, solid waste and toilet paper can stack upon itself with each use. This can lead to a dreaded pyramid plug. And even though you will be flushing the toilet, the water from the flush will simply drain past the solid waste and toilet paper and out the open black tank valve. 

Graphic of waste and paper above the water line in an RV holding tank creating odors from anaerobic bacteria off gassing hydrogen sulfide
Waste and paper above the water line creating odors from anaerobic bacteria off gassing hydrogen sulfide
  • There will be no water covering the solid waste and paper to keep odors at bay.
  • Leaving the black tank valve open will cause any liquid holding tank treatments to drain out immediately rendering them useless and wasting your hard-earned money.
  • Drop- in style holding tank treatments (pods, pellets and powder) will have little to no water to fully dissolve and activate them, again rendering them useless and wasting money.

 

Graphic of waste and paper below the water line in an RV holding tank keeping odors at bay with aerobic bacteria changing waste to carbon dioxide and water
Waste and paper below the water line keeping odors at bay with aerobic bacteria changing waste to carbon dioxide and water
RV black water holding tank waste valve in the closed position
Black water holding tank valve in the closed position

On the other hand, keeping the black tank valve closed will allow water to accumulate, allowing the bacteria to replicate and fully digest the solid wastes while covering solid waste and keeping odors away. 

So be sure to close the black tank valve while on full hookups. For further reading, click this link to the Unique Method. https://uniquecampingmarine.com/pages/unique-method

If you would like to read about if leaving the gray water holding tank valve open is a good idea, check out this article!

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