We used are "new" ( 21' fun lite) hi lo this weekend and all went GREAT. Very pleased with our purchase. Had one question though. Can both Black water tank valve and Grey water tank valve be left open at the same time?

I left the black water tank open until I needed to empty the greay tank.

Thanks...

It sounds like you were hooked up to full hookups? If so I've never left either the gray or balck valves opened all the time. I ususally don't dump until the tanks are some what full. If you leave the black water tank valve in the open position the solids and toilet paper will not disvolve, if the valve is left open the liquids will flow out leaving the solids and paper. If you let it sit in there in the liquid it will disvolve and flow out when you do finally open the valve.
When dumping my tanks I always dump the black water tank first. Then I dump the gray. As the gray water flows out some of it will go into the black water piping and tank and help flush it with gray water.
Hope this helps.
God Bless
Papa

Are asking about when you are emptying the tanks? You should empty the black tank first, then the gray tank second. That flushes the black tank residue out of the hose. Leaving the black tank valve while emptying the gray is okay. If you are asking about leaving the black or even the gray tank valves open all the time, that is a big NO,NO. I assume you can figure out why.

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Thanks....it does help....obviously I'm pretty new to this.

donm49,Don't feel bad about asking questions. I am still learning after owning our PreLoved preenjoyed for 11 yrs. Welcome to the forum.