Problems with stationary RV black water tank smell

[birdlady]

Hello.  New to this group. 
Can anyone tell me a good way to clean out the black water tank if we are not movable?  We have an RV parked on our property.  We've hooked up to electricity, have a water well with a pump, and the gray & black water drain into a septic tank.  (we keep the things closed & first, drain the black water ... then, the gray water when we leave)  Since we don't "move" & slosh the black water around, I think that's the cause of our smell.  Also, we don't put toliet paper down the black water tank; we bag it into our garbage.  Nothing we use seems to get rid of the smell!  We also pour clear water in after we drain the black water - when we are going to leave.  Any suggestions? 
Birdlady

[Steven]

Heres a few tips that may solve your problem.

When the tank level is empty or low, use lots of water when flushing solids. As the tank fills you can cut back on the amount of water.

The black tank should be at least 2/3rds full before you empty it to allow plenty of flushing action. If it's not full when you're ready to leave, add water.

Once emptied, refill the tank with fresh water and dump again. This doesn't have to be done every time but does help to flush all solids out.

Use a tank flush wand... it's attached to a water hose and the flush end goes down through the toilet into the tank. Again this doesn't have to be done each time you dump... only as needed.

After dumping and cleaning, close the valve and add enough water to cover the bottom of the tank.

Use Thetford Aqua-Kem holding tank treatment... the kind with formaldehyde...  as per instructions.

If you still have an oder problem after using this procedure for a few weeks then you may have a clogged vent pipe or you may just have a sour tank.

You can check for a clogged vent pipe with a drain snake or a water hose.

There is a service that can power wash the inside of the tank to eliminate the odor causing buildup.. see: http://www.allprowaterflow.com

I can't imagine where you got the idea that you had to bag your toilet paper rather that putting it down the toilet. Seems a bit gross to me.  I can assure you that if you follow the tips above there is no need to bag the TP. Millions of RVers flush the TP down the toilet with no problems.

[LindaH]

Use Thetford Aqua-Kem holding tank treatment... the kind with formaldehyde...  as per instructions.

Steven has given you some good pointers except for the above statement.

Since the OP said they were draining their tanks into a septic system, black tank chemicals with formaldehyde should NEVER, EVER be used in a septic system!!!  It'll end up killing all the good bacteria in the septic system and then it will go dead, entailing someone coming out to pump out the septic tank.

Many fulltimers never use anything except lots of water in their black tanks and never have any smell (think a bowl full of water for flushing solids).  If you feel you must use something in your black tank, there are all kinds of enzyme products you can use.

[kevin h]

Ditto on what Karen said.    The discussion of treatments vs water only are very popular on every forum I have visited.  The can get quite animated as proponents on each side try to convince the other that they are full of ....!

We are currently non-mobile and so do not get the sloshing action either.   We do NOT use any chemical products.  We DO put the tissue in the tank.   We do have tank sprayers but I do not use them each time I empty.

When the tank is ready to empty, it will be very obvious when flushing.  The flushing sound changes as the space in the tank fills up and the water line gets closer to the top of the tank.   We do not flush until the sound changes so we can get the most water movement as possible in order to move the solids.  Also, the longer we can delay the longer for the solids to break apart.

Note that I said "break apart".  My reading and experience does not indicate that the solids are broken down or biodegrade as they do in a septic tank because they are not stored long enough for the bacterias to do their thing.  These are called Holding Tanks, not septic tanks.   But, they will break apart if they are submerged for a while.

Periodically, perhaps every couple months, I use a wand on a hose to spray out the tank.

I turn off the water to the rig.  Run a separate hose with the wand directly from the water connection outside into the bathroom.  Push down on the toilet flush valve and stick the wand down.  I turn on the water for the wand and spend a good 10 or so minutes directing the strong spray around the inside of the tank.

I marked the wand so I know which way the water is spraying because I cannot see the nozzle when it is down below.  I find this very helpful.  It helps me control the direction of the spray and ensure all parts of the tank are cleaned.  Also, be sure to direct the spray up and down, not just on the top or bottom of the tank.

After you do this a couple times you will become very aware of the piping from your toilet to the tank and be able to get the tank very clean.

When the weather is very hot you will get a little odor when flushing.  This is normal as you are opening a hole directly into a tank containing some very odiferous things.  Warming things up increases that.  Also, if you have an exhaust fan going, it can pull a little bit of odor from the tank.  Although this is not pleasant, it is normal.   If you get a LOT of odor, or if it lingers, you may have a blocked vent as Linda pointed out.

On an aside note, if you get some bad odors be aware that your GRAY tank can be very smelly.  Also, if your rig sits for long stretches without water being introduced to the drains, the water in the P trap can evaporate which opens a pipe directly to your tank.   Simply pour some water down the drain to fill this back up which reinstates the odor barrier.

I get a little windy with my responses sometimes but I want to share as information as so many folks graciously shared with me when I first got started.

Good Luck!!!

[Bighill]

We use and have piranha tank additive for a couple of years with great results.

[Tony C]

When the tank is ready to empty, it will be very obvious when flushing.  The flushing sound changes as the space in the tank fills up and the water line gets closer to the top of the tank.   We do not flush until the sound changes so we can get the most water movement as possible in order to move the solids.  Also, the longer we can delay the longer for the solids to break apart.

Kevin and Karen, thanks for the info. Kevin, I learned some things from what you just posted, and would like to ask you, since you listen to the sound of the tank to see if its full or not, how often do you have to drain the black water.

We used to do it every 3 to 4 days because my wife said "the sound changed", and then we spoke to someone who said he does it every 2 weeks. Also, on the chemicals we use, it says it can last a week to ten days.  So, we are now draining the black tank once a week and that seems to work well for us. I was wondering what you and others feel about this time period and I am aware of the fact that it does depend on the tank size and usage. Ours is a 40 gallon and we are only two people.

Thanks again for the very informative reply.

[Tumbleweed]

Greetings,

  I've been living in a 22' Class C RV for about 10 years now.  I've never used any type of chemical or additive in the black water tank.  My toilet drops straight down into to the tank.  I can see the water level in the tank when it starts to get full.  I use that to know when to drain it.  I don't have it hooked up to the septic tank on the property full time so I have to move the RV when its time to empty the tank.  Its kind of a hassle but depending on how often I'm home, I go from draining it once a week to one a month.  I get a little smell when I flush the toilet (it opens straight into the black tank) but thats it.  I don't know what size the tank is.  I also flush the TP in the toilet.

  I flush the tank with fresh water one or twice a year at the most just to do it.  I haven't seen a need to do it more often than that.  Other than that, the only water that goes into the tank is when I flush the toilet. I don't know if that good or bad, but so far I haven't had any issues.

[jonnysmith006]

i also heard lot of piranha tank additive dose it really works that well as i have the same problem thinking of using it .

[luckyd]

The question of "how often" do you drain your black tank depends on
the size and the use.  My MH has a 50 gal B tank and takes several weeks to fill.
I also listen to the "sound".  I then add water to make it full so I can see the water
in the bottom of the toilet.  I then drain the tank. 
Every once in a while I will mix up several gallon of Calgon with hot water, add one
cup of laundry detergent, let sit overnight.  I then add water to fill the tank and then
drain.  Keeps the tank and probes clean and also no smell.