[Don]

I usually dump it the first thing when I get there … Because of transit most of the contents would be suspended in the fluid and washing around.

Then I close the valve, and just before I leave, I will dump it again, and give it a rinse.

Having no earthly idea as to whether this is right or wrong, I freely offer it up under the heading of “it works for me.”

BCO

[Archived]

They’re making a big mistake by leaving the valves open as solids will built up in the tank. You need that volume to properly empty the black tank followed by the gray tank as a rinse. I also rinse after each dump. The only time it would make sense to leave the gray tank open would be if you had lots of laundry to do, since most of the washers are water hogs. On my last dump of the trip, I also lean the bus over just a tad to port to be sure everything gets out while rinsing.

[Brian]

Just because some leave their tanks open should not cause a smell. The hose should fit tight on the ground fitting. If it doesn’t then it doesn’t matter if the valves are open. You have to realize not all RVs enjoy the same holding tank capacity that we do.

My routine is that the hose comes out when we are leaving, if staying for two days or less. Longer stays it comes out then and both tanks are emptied and the valves closed. I leave the hose attached at this point and empty the tanks every two days. Like many, if not most, I use the gray tank contents to clean out the black tank.

I use the tank flush on the last use and cleanout prior to parking the coach after a trip.

I’d say you’re procedure is common for those with large tanks.

[Archived]

The smell can come from the open valves, sewer gases rise through the hose and out your roof vent and would be a constant source of poo tinky.

[Ed]

Here is some very good information on tanks etc. from the Drainmaster.com website. I have their valves in my coach, and the site has lots of info. This is cut from a .pdf they have for download there.

1. The not-so-obvious dangers of leaving the Gray Valve Open

RVers sitting for long periods of time in RV resorts, etc. tend to leave the gray water valve open because it is inconvenient to go outside to pull the valve every few days. This practice leads to future problems with bad odors coming from the tank through the vent pipe or dry a p-trap. In addition leaving the Gray valve open allows the drained water to splash into the empty tank and the particulate in the water adheres to the sidewalls of the tank, and then dries!

2. How suction in your holding tank can be your best friend

Keeping the Gray Valve closed until the tank is 2/3rds full, and then opening the valve allows the suction created to pull most of the scum out of the tank and down the drain. With the valve closed as the tank fills a scum builds up on the surface not on the tank walls.

[Archived]

I do not leave my valves open but I would love to leave the big hose attached to make draining the gray water every 3-4 days easier. My Vantare has the bigger (Thetford) connections. I had never run into these on any of my previous RVs except for my parent’s 67 Airstream. Do most bus converters use them? If so, why?

I have never found a Thetford 90 and a 45 won’t go out the hole. By the time I put a Thetford/Standard adapter on, a regular 90 will not fit either. Therefore my plumbing bay door has to be open when the sewer hose is attached.

Anybody ever seen a Thetford 90?

DKO

[Bob]

Do as Tom says or you will run into that unfriendly character known as the “MOUND”.

Looks like this ……. only inside your black water tank.

[Doug]

I believe Ed needs to add prunes to his diet.

The poop will in fact accumulate in a pile if the tank drain is left open because there is not enough force or volume in the waste water to carry it out. What we have done is empty and fill at the same time. With a full fresh water tank and an empty holding tank we start out by emptying the one and filling the other. When we need to refill the fresh water tank the holding tank has a lot of head pressure because it is now near full. When the valve is opened anything on the bottom of the tank is literally swept into the drain hose due to the velocity of the waster water. In 22 years we have never had any issues using that practice. Of course our morning deposits are not the equal of what Ed apparently has.

[Gerald]

Reminds me of Jdub!

[Archived]

I had not considered sewage gases escaping through the gray water tank roof vent. Also appreciate the warning about the “mound”. Lots too learn

[David]

If you smell sewer gases the first thing to check is if the traps are filled. If you haven’t used a drain for a while the chances are good that the water in the trap has evaporated and that might be where you are getting the odors. This would especially be true if you are using a vent fan because as air is exhausted it is pulled in from thre outside and a dry trap could be just the path it needs.

Kitchen sink, shower drain, bathroom sink drains are all the obvious ones, but what about the washer for example?

Some coaches have roof vents that literally suck the water from the trap when driving because there is a vacuum in the area around the roof vent at speed and even though you masy have used a sink prior to traveling the trap has still been pulled dry.

Another issue could be related to a system vent that is not through the roof. Some fixtures such as a kitchen sink next to windows may not have a roof vent, but may have an air admittance valve. These are spring loaded valves that are closed by virtue of a spring and a seal. When water flows down the drain the valve opens and admits air into the drain to facilitate water flow. But if the spring or seal has gone bad, the valve remains open and the smell may be coming into the coach through this valve. It will look like a stand pipe downstream from a trap stopping just beneath a counter top. In that case the valve needs replacement.

[Archived]

Just for the sake of clarity I said the mound looked like that. And, THAT is an African subterranean termite mound. They can get to 30 ft. tall.

Here is another example.

You don’t want one of those in the coach either. And Jon, prunes won’t help that.

[Archived]

Bus people are full of it!

[Corey]

This coming from a used car guy!!!

[Archived]

The
only time it would make sense to leave the gray tank open would be if
you had lots of laundry to do, since most of the washers are water hogs.

I have teenage girls that take showers, a washer has nothing on that .. My wife and I have been talking about the need to tow a second freshwater tank after our eldist used half the dang pacific ocean one night to wash her hair.

We usually leave the gray tank open when we camp for more than a day. Then on departure, fill the black tank to the 3/4 point (presuming its not already there) and the gray tank to nearly the top and flush them both out. The plumbing on my conversion is such that I can run from the fresh water tank into either of the gray or black though a set of valves .. I tend to run the freshwater tank down to about 1/2-1/3rd when traveling so I don’t have all the extra weight, unless I know we will be boondocked for a night or two ..

When we get home, I fill both tanks and flush them 2 or 3 times each before storage.