Holding tank sensor issue

[rpns51]

Re: 2007 Roadtrek 190 Popular. We are on our first trip and are finding that even when we have emptied the grey and black water tanks, they still show 1/3 full. After 3 uses, they are reading "full". This does not seem accurate. Any feedback or ideas? Thank you, Bob Selby

[markopolo]

It's a common problem in most RV's (at least for me it is with the B, B+ & C RV's I own/owned).

Mine read 2/3rds full or even full after dumping. They'll both read empty after I really flush them out. Fill them with water and dump them until they read empty. Some people will put ice cubes in a half full black tank and drive around a bit and then dump it.

A clear sewer connector will let you see the color of what is coming out of the tanks. Flush them out until clear water is all that is coming out.

When we're away for while we just put up with it and know that we can go several days in between dumping.

Sometimes, about a half hour after dumping, the sensors will report the tanks as being empty.

[Ron J. Moore]

Seems a problem of sorts in most RV's. Last week, we emptied our RT190P and flushed with water; still would show one-third. I decided since I was ready to do it, I flushed both tanks with Hot Water and Dawn....drove around for about 45 minutes and flushed again....I'm into stupid all the time!! Stupid in that the soapy water flowed right out, I rinsed until no more suds appeared --- but damned one-third was shining brightly, ha!! It settled down on a run a day or so later. Safe travels, Ron J.

[Mike]

I've noted the same results. It usually shows a higher level of contents reading just after dumping.
I'm assuming the sensor(s) need a while to "dry" before it'll show the correct level of contents.
After a bit of driving after dumping, the levels usually read where you'd expect them to be.

[oschreiber]

Once I saw an article or a post recommending pouring an ice bag in the toilet, drive around for half an hour and then empty the
tank. People use that technique to clean coffee pots. Maybe this has been posted already.
Best regards.

[Mike]

I don't know how effective it is, but it seems a lot of people use it (ice in the holding tanks).
It gets mentioned on a lot of RV tips and tricks pages.
I'm trying to keep a bit of RV antifreeze in my holding tanks all the time, along with whatever
the tank treatment of the day happens to be.
I don't think it hurts, and it may help keep to seals and gate valves lubricated.

[Duffy]

We drop a 1/4 cup of Calgon bath oil beads down the toilet after emptying the holding tank and just leave it until the next tank dumping. This keeps the sensors clean and registering correctly. I don't think it would have to be that brand necessarily but it works for us.

[Y IZ IT]

My DD and SIL's TT was having the same problem. I read on numerous forums using Calgon and ice and take it for a ride. My SIL laughed and said no way, but my DD decided to try it. My SIL had TP on his face . It worked.

[Mike]

I've found that time is the best fix for sensors reading fuller than expected.
If we dump, and check the tank levels right away, they always still show the level
they were just prior to dumping, or just fuller than expected.
Check a few hours later or the next day, and they always
show green/empty. I think they just need a bit of time to dry.

We've never used ice cubes as a dump-aid, but it makes sense that it could help.