Grey valve open

............First off purchase some 'Dump Valve Lubricant' from Thetford , it works ! Dump Black tank whenever it gets full . About every 2 weeks pour half a gallon of bleach into gray tank and fill half way with water , then dump..........it'll clean out your sewer line . , jf

The best way I have found is to form a P-trap in the stinky-slinky. It eliminates sewer flies and odors from entering. I leave the grey water valve open at all times and only dump the black when necessary.
Works for us and has for the last 48 years of RVing.

lanerd wrote:
When leaving the gray tank open, won't a p-trap or duck bill keep any insect from coming up the drain?

And shouldn't the black/gray roof vent keep any sewer odor from entering the rv?

Typically the large drain hose ( 4 inches ? ) does not have a P trap.

And sometimes the roof vent is not enough for odors coming in from the sewer or septic, especially if they are driven by a strong wind.

Sam Spade wrote:
Can you....yes.
Should you......NO.

And what is going on with the black tank has no bearing on the right answer.

There are no "pros" except for being too lazy to go out and open the valve once a week or so......at the same time as you open the black valve.....which usually are side by side.

Well, Sam - you need to do some more detective work - or should that be "digging" before you suggest/accuse a poster of being lazy!..:(

Forgot the two things every plumber knows?..:@
(Only one of the two applies here)

Some folks have TWO gray tanks - the "normal" two (gray/black), and a completely separate gray for the kitchen.

For the (completely separate kitchen tank) set-up - leaving the kitchen gray open is fine - especially for us lazy types..:C

The black tank does have "bearing" (roller or ball?)..:S

Dumping the black tank contents, *followed* by the gray - helps move the black contents to the real sewer.
(The first of the two things every plumber knows)

Sooooo for the gray/black combo, as others have noted, "save" some (or all) of the gray contents to flush the lines and move the black tank contents after/following a black tank dump.

Open and dump the gray - as needed, when full and/or to facilitate a black tank dump.

The above is certified by Columbo as being the REAL deal!

:W

When leaving the gray tank open, won't a p-trap or duck bill keep any insect from coming up the drain? And shouldn't the black/gray roof vent keep any sewer odor from entering the rv?

Ron

I leave mine open. Have done so for many years and also full timing since 2011. Mine is 75G and if closed I am the one that is in the shower when the tank is full. Also with the clothes washer it's a bad idea since you can be close to full and leave while clothes are washing and cone home to water on the floor.

So at least once a month I close the grey tank and add about 40G and dump and flush. Zero issues!

We have always left ours closed and because we do, we escaped from potential serious damage. We own property in a small midwestern town that does not have separate sewer/storm water drains. During heavy rain, the system gets overwhelmed with storm water and it backed up into our sewer hose. If we had the grey tank valve open, it would have backed up in to our RV. Is it a rare occurrence-probably but you never know where the conditions could be right for this to happen. By the way, the first time this happened, the water also backed up into our garage (no house) so we have taken multiple steps so this does not occur again. We have a bathroom in the garage and the water poured in through the drains including the toilet. We had to remove all the wall board and dry out the insulation and the garage flooded with about 6 inches of standing water. Glad it was not in our RV.

grahampconrad wrote:
I am in a rv park for five months, and i am plugged in to sewar. Can i leave my grey valve open all the time except when i flush? THANKS in advice. I know there are pros and cons on this, but i would like the Right ANSWER.

More solids that you realize go into the grey tank. Leaving the valve open all the time just allows it all to build up that much more. Shut it, then drain =after= draining the black tank. This will help rinse more of the solids out =and= rinse the hose after draining the black tank.

FWIW, we stopped doing dishes in the sink, and use a basin instead. We then dump it in the toilet. Keeps food and grease from going in the grey tank and gives us more water in the black to help keep us from the dreaded poop pile.

Lyle

Besides sewer gases, sometimes sewer roaches can enter your tanks also, when leaving the valves open for extended periods.

Turn Key wrote:
You can but I wouldn't. Sludge will build up and dry in the bottom of the tank causing issues down the road. Better to let the grey water fill the tank and then drain it every few days. Will keep the sludge moist and allow it to drain away with the water. Your call, though.

Happy Camping!

^^^ THIS ^^^

To a lesser extent, soap scum and some food particles can build up in the tank. (although we wipe away all food particles prior to washing) As with the black tank, emptying large volume all at once helps to drain most of that out of the tank.

Letting water just flow out often leaves soap scum and food particles behind to dry out.