My rear black tank didn't empty....

[CoMaddMax]

RV newbie here... I have 2 BW tanks and one valve to empty. I emptyed the tanks (I thought) but when I went to add the toilet chems the rear tank was still 1/2 full. Any ideas why? No turds in the back tank which has a 1/2 bath feeding it.

[007matman]

Originally Posted by CoMaddMax

RV newbie here... I have 2 BW tanks and one valve to empty. I emptyed the tanks (I thought) but when I went to add the toilet chems the rear tank was still 1/2 full. Any ideas why? No turds in the back tank which has a 1/2 bath feeding it.

It's reading full on the digital guage or you found a way to peek inside and visually saw it was half full?

[mwdilday]

Originally Posted by CoMaddMax

RV newbie here... I have 2 BW tanks and one valve to empty. I emptyed the tanks (I thought) but when I went to add the toilet chems the rear tank was still 1/2 full. Any ideas why? No turds in the back tank which has a 1/2 bath feeding it.

Maybe there is a second dump valve?

[fonzie]

Post your type of RV you have, model number and year. It will help provide better feedback. Probably you have another black tank valve somewhere hidden.

[owgpz]

This is a long shot, but it sometimes happens. When the rig is being built and a hole saw is being used to punch the fitting holes, sometimes a tired or careless technician will leave the sawed out piece within the tank. Then when the conditions are just right, that circular piece of blank tank will perfectly fit over the drain opening.

[CoMaddMax]

It is a new 2016 Spartan 300 3912X.

[CoMaddMax]

After dumping the tanks, I could see the front tank floor in the front toilet. I looked in the rear toilet and the water is about 12-16" from bottom of the toilet drop tube.

[Flybob]

Put some water on the tan you think does not dump and see if it will come out the dump valve. You can not judge the level in the tank by the lights as they malfunction often. All it takes is a small amount of crud or foam to stick to the sensor and it will misread.

[fonzie]

If you have same RV as below, look at time frame 0:56 sec as there is a valve handle inside a compartment. Maybe that is second black tank.

https://www.youtube.com/watch?v=yBChCdI1pzQ

[CoMaddMax]

Thanks for the video, that's my beast and that is the only handle that I know of. Taking it in for some warrenty work so maybe the dealer will know... I'm not holding my breath though, cuase the dealer's service dept is lame. They have a used one for sale so maybe I can contact that owner.

[WilliamG]

Look on the frame rail from the tires back. A lot of units have a second pull handle there and you have to reach under to pull it.

[hikerpatrick]

I had my tires rotated at Costco years ago. My dump valve would drip once in a while. Anyway I went in the store and shopped. Came out and a pool of raw sewage was under the rig. I went to the mechanic and apologized and said I'd clean it up. He said no... that it was his fault. He saw the t-handle and wondered what it did........
That is what is called an "Oh Chit" kinda moment.
I now have two dump valves installed.

[beavs4au]

Originally Posted by CoMaddMax

RV newbie here... I have 2 BW tanks and one valve to empty. I emptyed the tanks (I thought) but when I went to add the toilet chems the rear tank was still 1/2 full. Any ideas why? No turds in the back tank which has a 1/2 bath feeding it.

I know I have a different model then yours but having two tanks it should have two valves.Mine actually broke of and had to get it fixed.Just saying look for another hole in the frame where a valve handle could be.

[mnoland30]

Since you are new, take a minute to google the GEO method. It works. TST treatment from Walmart is also a very inexpensive and effective treatment. I bought a hose extension with a adjustable spray nozzle on the end to spray the sides of my tank. I was amazed how much crud was still left in the tank after just dumping.

[CoMaddMax]

WooHoo! I found it! It is right in front of the tires on the drivers side. Thanks to everyone who posted and especially hikerpatrick, his post led me to look closley around the tires!

[dwayneb236]

Gotta love where they install some of those valve handles. I have two gray tanks on mine. One for the bathroom of course and one for the kitchen. The bathroom is easy to get to. In the front compartment. The kitchen gray tank is on the drivers side in front of the tires. Right under the bunkhouse slide. I get to crawl under there when it's time to empty. Have hit my head, back, arms, you name it. Nothing fatal though. I have finally got smart and ordered extensions to put on when the slide is out. No more crawling.