I can’t be the only one with a poorly designed black tank.

[PsnRebel]

Let me preface, this is not my first rv (it is my 1st Class A pusher) and we have 30+ years experience mostly boon docking, but do spend time in campgrounds also.

With that said, two years ago we retired and bought a used 2005 Mandalay Presidio. From the very first trip, at a campground with full hook ups, we were lucky enough to be introduced to a poop pyramid, that literally “exploded” when opening flushing the toilet. Getting black waste everywhere. Wonderful.

I always leave water in the bottom of the tank after flushing to assist in breakdown etc. When traveling (and occasionally when parked) there’s always an odor.

Traveling down the highway, the poop pyramid has been known to resurface. Every time this occurs i dump the tank as soon as possible, but it doesn’t correct my issue easily and immediately.

I now know what the issue is, this is where i need help. The main, large portion of black tank is not directly under the toilet. The inlet from the toilet is at the far right end of tank. This area of the tank might be 10” tall, in theory the solids are supposed to travel along an ever so slight grade, about 12” towards the larger portion of the tank where they are supposed to fall into the a much larger holding area. This is where the sensors are and main capacity of the tank is. The liquids of course run off this “shelf” with no problem. Leaving behind the paper and solids to slowly accumulate. Filling the bowl full of water before flushing only may delay the inevitable, but it eventually rears its ugly head.

When dumping the tank the only way to clear this area of the tank is to fill the tank with water to near capacity. There is a factory installed sani flush that is on the top of the tank, but not really anywhere near where the pyramid begins to form.

I don’t know how to solve this. I thought i could add another black tank flush where the pyramid forms, which may work, kinda when on city water. I don’t believe the onboard pump will have enough pressure to be effective if i plumb in it a way it could use it when not connected to city water.

So frustrated. Any ideas? Sorry i cannot get a good picture of my tank setup to give a better idea. Picture an upside down “L”, or an “L” shape where the long vertical line lays horizontal and the smaller horizontal line is now vertical.

Thanks in advance.

[ScottG]

I recently watched an RV repair channel where they found there was no seal under the toilet and was causing all kinds of stink.
Also, If there's an Air admittance valve under the sink, I would replace it with a quality unit (anything but the black ones) from Home Depot, Lowes, Etc..

[PsnRebel]

enblethen wrote:
I doubt whether you are getting rid of solids in the tank.
Something like Drainbo this or similar products to truly breakdown septic tank solids may work.
You will have to fill tank to at least half to get it to work.

Thanks, but filling the tank even 1/2 way wont get the liquid to “rise” into the shelf area of the tank. But i do understand what you’re saying. Maybe i need fill the tank with water and draino like product and let it sit?

[enblethen]

I doubt whether you are getting rid of solids in the tank.
Something like Drainbo this or similar products to truly breakdown septic tank solids may work.
You will have to fill tank to at least half to get it to work.