Using Roebic K-57 to clean tank sensors.

I little background first.
We've been living full time in our RV since the end of October. I have 3 tanks. 1 black and 2 gray. They have tank level indicators which read Empty, 1/3, 2/3 and full. For the past month, all the tanks read 2/3 even when they're empty. What else is new. The full light does go on when it's time to dump.
I contacted Roebic and spoke to a manager in the R & D department. I explained my situation and she said to dump 16 OZ of K-57 in the tanks and let them sit as long as possible. I did it to the galley tank because that's the one which fills the slowest. I filled and dumped the tank a couple of times before adding the K-57. The last time I filled it to the point where the full light lit. I then added the Roebic. I was able to let it sit for 72 hours before I had to dump it. The results was that when empty, the 1/3 light is lit. Better than before so the K-57 did work. I wish I could have let it sit a few more days.
We are going on a 10 day cruise the end of January and I'm going to do the same thing to all the tanks and they'll be able to sit for 10 days. I'll let you know what happens when we come home and dump all the tanks.
She also said that K-57 would be better in my case and not K-67. K-67 would be for a plugged line or trap.  She also said that Roebic has chemicals for black tank and gray tanks. 2 different chemicals. I don't know if I want to be tied to having to use chemicals. I haven't for the last 20 years and don't want to start now. I'll have to think about that.
I purchased the Roebic K-57 at a Tractor Supply store.

Looking forward to your results with the 10 day soak.

Enjoy the cruise,

Tom

After 5 years of reading 1/3 full, I finally got my black tank to read empty with a product called Happy Camper.
http://1-happycamper.com/products.php

I used Roebic 57 or 47 to clean gunk off tank walls for about 10 years, with generally good results. Rid-X works too, but I always preferred the Roebic products. Three days is about the minimum to get decent results and longer is better.  Most of that time I had external sensors and just needed to reduce the slime coating on the tank walls.  If you have internal sensors, results are more chancy because the internal sensors can catch shreds of paper that may later dry into a solid mass on the sensor when the  tank is emptier. Those can be nigh impossible to remove, even with a long soak and Roebic or Rid-X

Well I have the results after the tanks sat for 10 days with 16 oz. of Roebic K-57 added in each of the 45 gallon tanks.
The first thing I did was dump the black tank and I flushed it a couple of times. I then dumped the gray tanks. All three tanks now read 1/3. The Roebic may have helped a little. Maybe just using fresh water would have accomplished the same results.

I know this is an old topic, but I had put K-57 in the tank couple of week ago. Now due to the Covid-19 virus we are ordered to stay home. My trailer is at a storage facility.  I will not be able to empty my black tank for some time. Do you see any risk in leaving the Roebic K-57 Treatment in the blank tank for an extended period of time.
Thanks.

No risk at all. It's merely a biologic agent, adding yeast-like microbes that will digest wastes, grease, and scum.  They just eat until its gone, or at least as much as they can reach.

Just to clarify, dump the K-57 into a flushed and empty tank or a flushed tank with clean water added?

I would dump and flush the tank then put in maybe 15 or so gallons of fresh water. Then if you could drive around to let it slosh around splashing your sensors would probably help and to make sure all the solids get splashed. .

You want the tank full of liquid so the good microbes can reach all parts of it.  Flush the tanks as well as you can, then add fresh water and the K57 (or RidX or similar) and let it percolate as long as you can manage.

Tanks with internal sensors (the pins go thru the tank sidewalls) don't clean up as well as those that have external sensors. The pins get clogged with toilet paper and solids can build up thickly as well. If the tank has been had years to accumulate the sludge, a few days of biological soaking isn't going to magically cure it. It helps, but miracles are rare.