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Cleaning Black Tank Sensors/Installation of SeeLevel II
During the last 18 months, we tried most of the recommended remedies for cleaning the black tank sensors so that they would be more accurate.  Our sensors had read 1/3 full when empty.  The 2/3 and full sensors were fairly accurate.

Last August and September, we followed Larry Wade's suggestion to fill the black tank (3/4) and let it “cook” during those hot days and nights for 2-3 weeks.  We added a cup of  RID-X RV Toilet Treatment and gave it a 3 week cook.  After a short trip, we flushed the tank and did a second treatment for another 2-3 weeks.

A second step that might have helped is I cleaned the external black tanks sensors with a brass brush and water resistant silicone and sealed the 3 fittings with dielectric grease.  If it didn't really help, it certainly didn't hurt.

At this point, the readings for 1/3 full were sporadic. 

Early in February, I added a ½ cup of heavy duty dishwasher (gel) with 4 gallons of water and drove 125 miles before using the toilet.  I repeated this last step earlier this week and now the blank tank reads empty with less than 7-8 gal (estimate). 

According to the original owners, the black tank sensor gave them trouble during the first year.  So those sensors were probably crusty for a long time.  I believe that Larry's suggestion and the dishwasher gel finally cleaned the internal sensors.

My strategy going forward is to do the 3 week summer cook once a year and use a ½ cup of heavy duty dishwasher after each dump and flush if we going to store her for a few weeks.
Re: Success with Cleaning Black Tank Sensors
Reply #1 –
Ed, you've tackled a lot of projects in the relatively short time you have owned your LD.  And inaccuracy of the 1st sensor is something you can live with. But installing a Seelevel monitoring system will show you've made a jump to the big leagues.

After installing Seelevel, we know we can go longer between "pit stops". And when the nearest dumpstation is a half day drive in Yellowstone....well it saves us a lot of time and probably gas too.

Not saying your tank cleaning strategy is not important.
Steve K.
Steve K

2003 Mid-bath
Re: Success with Cleaning Black Tank Sensors
Reply #2 –
Our Seelevel has been giving inaccurate reading on the black tank for quite some time now. I replaced the sensor which did not fix the problem. We have tried a variety of fixes which haven't worked. Since we full time we can't employ the fixes suggested here.

As a result we plan on having the tank pressure cleaned when we visit Yuma in the near future. We know two people who have done this with success including one fulltimer who has done it twice on his class A. The downside is the cost, $200. They do both tanks.

Will let you know how that turns out.

Jim
 
Re: Success with Cleaning Black Tank Sensors
Reply #4 –
"...we plan on having the tank pressure cleaned..."

???  I'm not understanding this statement! You are aware that the sensors for the SeeLevel System are located on the 'exterior' of the tank, are you not? How will having the interior cleaned help with that? The SeeLevel sensors function by capacitance through the tank, sensing the level of the effluent as it falls or rises past vertical points on the sensor, resulting in a % of full/empty.

Have you called the SeeLevel folks to voice your concerns?
Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: Success with Cleaning Black Tank Sensors
Reply #5 –
Quote from: Lazy Bones  - 
"...we plan on having the tank pressure cleaned..."

???  I'm not understanding this statement! You are aware that the sensors for the SeeLevel System are located on the 'exterior' of the tank, are you not? How will having the interior cleaned help with that? The SeeLevel sensors function by capacitance through the tank, sensing the level of the effluent as it falls or rises past vertical points on the sensor, resulting in a % of full/empty.

Have you called the SeeLevel folks to voice your concerns?

Have talked to the SeeLevel folks and no solution. In fact, discussed it with them prior to ordering a new sensor. It's my understanding that the sensors are sensing the thickness through the walls and the theory would be that buildup would throw that off. It is off from the start after emptying them. It seems to be accurate as it gets much closer to full.

Jim
Re: Success with Cleaning Black Tank Sensors
Reply #6 –
Quote from: Ed D.  - 
Ever try these?
I use one to clean my black tank now and then. Works well.
Ed

Amazon.com: Camco 40074 Flexible Swivel Stik with Shutoff Valve: Automotive

Amazon.com: Valterra A01-0187VP Flexible Tank Wand: Automotive

I have tried the wand which did not fix the issue. Maybe it has something to do with the fact that the toilet outlet doesn't open directly into the tank. I don't know.

Jim
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: Success with Cleaning Black Tank Sensors
Reply #7 –
"Maybe it has something to do with the fact that the toilet outlet doesn't open directly into the tank."
---
I've used the Valterra flexible tank flushing wand for many years; the TK has a straight drop from the toilet into the tank, so this configuration allows efficient use of the flexible wand. It can sometimes be a little inconvenient to put the hose through the bathroom window, but the overall process goes quickly.

As ever, YMMV.
2003 TK has a new home
Re: Success with Cleaning Black Tank Sensors
Reply #8 –
Jim

A little research never hurts and even leads to more/better understanding. So I went to the Garnett web site and started poking about. In Chapter 4 of the Owners Manual I found what might be the answer you are looking for. It is said; "If sludge buildup in the tank becomes extreme the gauge will cease to operate properly". It also suggests that a cleaning may be helpful. So, as you indicated, perhaps a trip to Yuma may be to your benefit.

And, as I said earlier, the sensor's reading is derived by 'Capacitance'. A capacitor is two conductors separated by a dielectric material, in this case the circuitry in the sensor and the liquid in the tank, separated by the tank wall. If that tank wall should increase in thickness (such as would occur with sludge buildup) then the measurement would be inaccurate or intermittent or non-existent.

https://www.garnetinstruments.com/wp-content/uploads/2015/12/709-709-PH-Manual_v3.2.1.pdf     ;)
Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: Success with Cleaning Black Tank Sensors
Reply #9 –
Jim and Gayle, as you fulltime like me, giving your black tank soak time is a challenge. 

As pointed out, the sensors read through the wall, and encrustation can throw them off.  Being way off at low levels and more accurate as the level rises is consistent with that.  Think about this - you want to soften and loosen the deposits, then provide something physical to loosen the stuff on the walls. 

When things got bad for me, after months of being unable to do a tank flush, I finally had the ability to do a thorough cleaning.  I started by dumping, then I filled about 2/3 to 3/4 with the warmest water I could manage.  I started by turning on the water heater, and by filling several pots with water and putting them on the stove.  When everything was up to about 140 deg., it all went down the toilet.  I added water until my SeeLevel read 75%, and I added about a half cup of laundry detergent.  (Add the detergent last, else you may have soapsuds on your roof - don't ask how I know this.)  Let it soak overnight.  Dump, rinse with a flush wand, then re-fill to about 2/3.  Add a few bags of ice cubes to brush against the inside walls, and drive a winding or rough road for an hour.  Dump, rinse with the flush wand, then check your SeeLevel reading.  Mine read 0 for the first time in 6 months. 

It is a pain, but less expensive than $200...

Ken F in NM
'08 MB
Re: Success with Cleaning Black Tank Sensors
Reply #10 –
Quote from: Kenneth Fears  - 
Add the detergent last, else you may have soapsuds on your roof - don't ask how I know this.

I know how to do that and it was easy!  LOL.  Sure glad that only DW saw the error of my ways.  You never saw anyone clean up soap suds so fast while trying to look composed. That was on day 3 of ownership.
Re: Success with Cleaning Black Tank Sensors
Reply #11 –
Ken

"I started by dumping, then I ..."

I'm glad you found a system that works for you!

That having been said I would wager that I could solve Jim's problem with a lot less effort. All it would take is less than a bottle (12oz) of Eco-Save, a bacterial/enzyme RV tank treatment.

Eco-Save Products, Green long before it was Fashion!!

I also have the SeeLevel System that Jim is having problems with. I was using Eco-Save long before acquiring my LD and now continue to add 1oz each time following a dump. I've never seen any indication of false readings since my SeeLevel System was installed by Mike Sylvester many years ago.    ;)

Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: Success with Cleaning Black Tank Sensors
Reply #12 –
I remember, in the past, it has been suggested to put ice down the commode and drive around to mechanically clean the black tank and sensors. Has anyone tried this with success?
Greg & Victoria
2017 Mid-Bath  “Nocona” towing a manual 2015 Forester
Previously a 1985 TK
SKP #61264
Re: Success with Cleaning Black Tank Sensors
Reply #13 –
We've never paid any attention to the black tank sensor since they are often so inaccurate.  We can tell by the sound when flushing when it's getting full.
Linda Hylton
Re: Success with Cleaning Black Tank Sensors
Reply #14 –
Thanks Ken and Steve. Will look into those options.

Jim
Re: Success with Cleaning Black Tank Sensors
Reply #15 –
And this thread is why I love this LD group......
Rebecca in WA
2016 mid-bath
"Ramirez"
Re: Success with Cleaning Black Tank Sensors
Reply #16 –
"I remember, in the past, it has been suggested to put ice down the commode and drive around to mechanically clean the black tank and sensors. Has anyone tried this with success?"

   Greg, I saw a youtube on this subject, they say it does not work.  Maybe there might be a different result with our tanks?

http://www.youtube.com/watch?v=iH6acEmqvcw

        Karen~Liam
            98~MB

1998 ~ MB  WanderDaze
previously a 1984 Winnebago itaska- The Road Warrior, before that several VW Buses and before that a 1965 Chrysler Convertible Newport or our 1969 Chrysler La Barron with an ice box and a couple sleeping bags
Re: Success with Cleaning Black Tank Sensors
Reply #17 –
Any method that cleans the sensors will work until the next time the tank is used then all bets are off.
Could care less what the idiot lights say.
We know from experience that after 6 days, it's time to find water and a dump station.
Ed
Re: Success with Cleaning Black Tank Sensors
Reply #18 –
Quote from: HiLola  - 
I remember, in the past, it has been suggested to put ice down the commode and drive around to mechanically clean the black tank and sensors. Has anyone tried this with success?
Not sure if driving around with a couple bags of ice floating around in the tank makes much of a difference.
It's sort of an RV old wives tale, something people have done for years without knowing if it is effective.
Guess we could install a couple of holding tank cams and see for ourselves.

Just driving  will agitate the contents, something we regularly do, since we regularly dump at home.

Before leaving for home, I will often pour a cup of dishwashing soap into each tank. Much of the buildup in holding tanks is grease based. The detergent help breaks it down, during the drive home.
Seems to work. Our 14 year old tanks are free from buildup and the tank sensors still work, although we use a SeeLevel for more accurate readings.
What the dishwashing soap doesn't dissolve,  will be taken care of by the annual summertime enzyme soak.

Larry



Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Success with Cleaning Black Tank Sensors
Reply #19 –
Quote from: Ed D.  - 
Any method that cleans the sensors will work until the next time the tank is used then all bets are off.
Could care less what the idiot lights say.
We know from experience that after 6 days, it's time to find water and a dump station.
Ed

EXACTLY!

And you if always use the fresh water tank, it pretty hard to fill both the gray and black tanks from one freshwater fill up.
35 + 28 is more than 58 in the fresh water [MB specs]
Don & Dorothy
Sold our LD in June of 2023

Our boring always non-PC travel blog
Traveling Dorothy
Re: Success with Cleaning Black Tank Sensors
Reply #20 –
Quote from: Don Malpas  - 
And you if always use the fresh water tank, it pretty hard to fill both the gray and black tanks from one freshwater fill up.
35 + 28 is more than 58 in the fresh water [MB specs]
When boondocking for long periods, we never completely fill the holding tanks.
We can carry an extra ten gallons of water, to utilize the extra available tank space, and add an extra day or two, before looking for a dump and fresh water.

Larry.
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Success with Cleaning Black Tank Sensors
Reply #21 –
I agree that ice is an old wives' tale.  That does not mean that it is not effective.  In the film, the test focused on dealing with a solid mass on the bottom of the tank.  Everything I have read about using ice focused on removing deposits from the sides, not the bottom.  To get the ice to the sides, it must be floating on enough water so that, as the surface sloshes, there is a rubbing of the tank sides by the sides.  The guy in the film said that the ice could be stopped very easily, so it could not be effective.  (Hmm, I wonder why the Titanic sank, then?)  I do know that ice, floating on water, hurts if it bumps into you.  I suspect that a mass of floating, sloshing ice cubes can add mechanical scrubbing to simple sloshing.  Besides, it is cheap. 

When several flushes had failed to clean the sides of my tank, I added about 10 gallons of water, then put two large bags of ice down the toilet.  I drove for about an hour, then dumped and flushed.  For the first time in months, my SeeLevel gauge read zero.  Would a third soak and flush, without ice, have cleaned the tank for me?  Maybe.  I have no way of knowing.  What I do know is that SeeLevel was telling me I had a black tank approximately 1/4 full after the second dump and flush.  After the water and ice, then dump and flush, it read empty.

Ken F in NM
'08 MB
Re: Success with Cleaning Black Tank Sensors
Reply #22 –
Quote from: Karen & Liam  - 
"I remember, in the past, it has been suggested to put ice down the commode and drive around to mechanically clean the black tank and sensors. Has anyone tried this with success?"

   Greg, I saw a youtube on this subject, they say it does not work.  Maybe there might be a different result with our tanks?

http://www.youtube.com/watch?v=iH6acEmqvcw

        Karen~Liam
            98~MB


Interesting, thanks for the video!
Greg & Victoria
2017 Mid-Bath  “Nocona” towing a manual 2015 Forester
Previously a 1985 TK
SKP #61264
Re: Success with Cleaning Black Tank Sensors
Reply #23 –
This is a summary of our recent Garnet 709 SeeLevel II installation.  Adding it here because it is the most recent relevant thread I could find.  And because this thread, among others, inspired my wife and me to install the SeeLevel II monitor.  It also inspired us to adopt the use of Eco-Save.  The contributors to this forum are awesome.

My wife and I have a new-to-us (since June) 2011 27’ MB.  We love it.  It is well outfitted and was very well maintained.  But, until this week, it had only the stock tank level monitors, which are near useless, as has been well established on this forum.  Hence our first meaty diy upgrade.  (We have also added a water filtration system that I will write about soon.)

The SeeLevel installation went flawlessly, if slowly, thanks to posts on this forum and to two comprehensive articles, one in the Lazy Daze Companion, and the other in Andy Baird’s blog:

The Lazy Daze Companion: SeeLevel Systems Monitor
Tank gauges

We purchased the 709 SeeLevel II from rvupgradestore.com.  The bundle included three 12” SE tank sensors, which was perfect for the MB.  The price out-the-door was $184, including shipping.

We placed sensors on the tanks as directed in the Garnet installation guide.  If a sensor length allowed for a slight adjustment up or down, within the parameters of the instructions, we adjusted slightly up on the black and gray tanks to get the most accurate possible reading of “full” (100%).  The fresh water tank had no wiggle room, the bottom of the sensor wound up right at the top of the outlet to the water pump.  We think (hope) this will give us a pretty accurate indication of empty, with near-instant, real-world confirmation.  :)

Highlights of the install include:
  • The grey tank sensor was placed on driver's side of the tank, adjacent to the propane tank.  The metal propane tank is far enough away that it doesn’t interfere with the sensor’s performance. The Garnet install instructions are specific about proximity of a sensor to metal and routing of the sensor wires away from the left side of the sensor.
  • The black tank sensor is located on the passenger's side of the tank, to the right of the stock sensor and adjacent to where the stock sensor wires pass through the undercarriage into the basement of the galley sink cabinet, where the water pump is located.
  • The fresh water tank sensor is placed under the galley drawers on the passenger's side, forward toward the oven.  It’s an awkward location that taxes dexterity and patience.
  • New 18 awg marine grade wire (Ancor) was used.  I bought 25’.  That was barely enough.  If I had to do it again, I would get 30’ and not worry about every little bit of waste.  I also used Ancor marine-grade connectors.
  • To get the new 2-wire pair from the undercarriage to the galley sink basement, we drilled a new 1/4” hole immediately adjacent to the existing hole.  I was very cautious locating the hole.  The result was perfect.
  • To get the new wires from below the sink to the cabinet above the sink, we ran the wires through the black tank vent pipe.  I came to this solution reluctantly, but after looking at alternatives, bowed to those with MBs who have gone before me.
  • We located the monitor in the small space between the range hood and the microwave, an absolutely perfect spot.  See the photo below.
  • As recommended in the articles, I taped the sensors in place, otherwise completed the install, and tested the system.  It worked perfectly.  Then I permanently affixed the sensors and covered them with 3M undercarriage spray.

See attached photos, fresh water tank excluded (no way to photograph).

Happy to add detail. Please ask.

Many, many thanks to the many Lazy Daze Owners' Forum contributors who collected and posted the information that made this process so much easier for my wife and me.  The worst of the process for me is that I’m bruised and muscle-sore from crawling around under the rig.  Yeah, what doesn’t kill you…

Jim

Jim & Sue
Formerly owned: 2011 27' MB, Sidra
Re: Cleaning Black Tank Sensors/Installation of SeeLevel II
Reply #24 –
Quote from: Karen & Liam  - 
"I remember, in the past, it has been suggested to put ice down the commode and drive around to mechanically clean the black tank and sensors. Has anyone tried this with success?"

   Greg, I saw a youtube on this subject, they say it does not work.  Maybe there might be a different result with our tanks?

http://www.youtube.com/watch?v=iH6acEmqvcw

        Karen~Liam
            98~MB


I love when grown-ups do science fair projects & really geek out the whole thing (including buying "a recipe for simulated waste from NASA").  Thx for sharing..

P.S.  Ldy Lulubelle has a straight shot into the tank, so I can eyeball things (& I do when running the hose through the bath room window), but the idiot lights on the rang hood have worked for me so far,

Lynne


Lynne
LDy Lulubelle, Green '05 31' TB
Lilly, the 4-Legged Alarm