Storing RV - Tanks Wet or Dry?

[JDinFbg]

I have read multiple post in this forum and others about whether to store ones RV with the tanks wet or dry. I have always drained my tanks before storage (anywhere from 6 weeks to 3 months), but do not drain the pipes except over winter when sub-freezing weather could happen. This means that when I periodically check my RV in storage I have to take along a jug of water to replenish water in the toilet bowl. If I left some water in my fresh tank I could simply turn on the water pump for this. Some have opined that RV tanks are never truly "dry" since residual moisture and condensation will remain. Some have opined that keeping some water in the tanks will keep the drain valve seals wet and reduce problems.


So my questions. Has anyone actually had drain valve seal issues by leaving tanks drained? If you leave some water in the black tank, do you add some kind of tank treatment to work on any residual gunk that may remain in the tank? How much water do you leave in your tanks when being stored for an extended period of time? What about winter when it could freeze, do you leave water in your tanks?

[be-happy]

For me there is a big difference between summer storage and winter storage.
Summer storage or should I say in between trips, I leave the plumbing system as is. However the fresh water tank I do empty and fill to 1/3 before heading out again. I my self find no reason to drain the system, do you drain your house system when you leave?

Winter everything gets drained and emptied. I use the RV antifreeze in winter and keep it in the lines. Through the process antifreeze gets into the black and gray tanks and stays the winter.

Knock on wood I have not had any type of seal problem with what I am doing.

[Lantley]

For the most part you cannot totally drain your tanks even if you try. Some residual water will always remain. The bottom of the tank is not totally level or flat.

[Persistent]

Fredericksburg TX may be a lot different than Beaver Dam WI. Condition of your tanks may also be an issue.

Freezing
Water pipes, valves, faucets, and fittings can freeze and break even in short periods of freezing weather. Full tanks make take more than one day in freezing weather to cause freeze damage. A little water in plastic tanks will not likely cause damage. Small amounts of water in drain pipes and wet valves will probably not be a problem.

Black and Gray tank valves should be stored closed. Shape of the plastic seals is better maintained.

Avoid antifreeze in fresh tanks. It is almost impossible to get it all out later. Just drain and leave fresh tank drain valve open. Small diameter valves are usually okay open.


Heat
Long periods of extremely hot weather can dry out and damage plastic water systems. Heat and high humidity can grow things.

Moderate Weather
Cool, dark, wet things are usually okay. High humidity can still grow things.

Fresh Water System
Home water systems are usually dark and cool. They remain under pressure at all times. This has proven to be a good strategy for potable water systems. If pressure drops, they are no longer considered safe. Municipal water systems issue "Boil Water Advisories" if pressure drops too low.

Storing fresh water in RV tanks and pipes can go either way. It does not seem to generate hospital visits whether fresh tanks are stored empty or full for months at a time. To be safe, bleach your system if it has been stored either full or empty for months.

Black and Gray
Black and gray tanks seem to perform better when stored empty. The issue there is garbage and solids accumulating in tanks. Dried garbage and solids are extremely difficult to remove. Over a period of time dried solids can accumulate. Wet garbage can generate significant stink.

In Texas you are probably more concerned about accumulation of dried solids in tanks. Very hard to remove. Solids accumulating in black tanks have been know to plug the toilet drain completely.

I have experimented with various chemical additives over the years. I found the just plain water works best. Possibly a little Dawn Dish Washing Liquid helps. Chemicals eventually screw up a system.

Draining and flushing a black tank is the most important activity. Getting all the solids out is the goal. I use a transparent plastic drain fitting to observe when all the solids are out. I use the built in tank flush to refill and re-drain the tank until wet solids stop coming out.

To get the tank level gauges to work correctly I put 5 to 10 gallons of water in the tank when I drive 100 miles or more. The sloshing usually wets and removes dried scum. Drain and flush when I get to my destination.

In high dry heat situations, you may wish to keep the tanks wet. 5 gallons may keep the bottom of tanks, drain pipes, and valves wet so they don't accumulate hard dried scum or other solids.