[Richard]

I could only imagine that most of you lay awake at night thinking about replacing your waste tank sensors. Ok, maybe not. Some of mine were giving erroneous signals indicating the tank was partially full when it was not. Since the bride was well tuned in to the sensors in order not to overflow the tank, I received requests (multiple) to correct this situation. I delayed because I had heard horror stories about getting the old ones out. 

Getting them out is easy. Seriously, but you have to understand how they seal to make it easy. The screw you see threads into a nut on the other side of the rubber grommet. Tightening the inner nut on the screw tightens against the nut on the other side of the grommet, squishing the grommet, and sealing the hole. If you simply pull on the screw head you compress the grommet even tighter in the hole. Back both the nuts off toward the screw head, push the screw into the grommet about 1/4 inch. Put a small screw driver behind the lip of the grommet and pry the grommet out. If you can get a pair of needle nose pliers between the grommet flange and the tank, it’s even easier. 

It took more time to put the zip tie protective covering on the wiring than it did to change all five sensors. And go ahead and remove the fancy water bay covering to gain access. It would be very difficult to do with the cover in place. 

Oh yeah, it’s a good idea to empty the waste tank before starting the process.

[Robert David Smith]

Hi Richard,
Yep, Robert again (#431) got the coach back, it now looks great, but noticed small leak happening (i suppose when it shakes things break) from the bottom of the waste tank. Yes, I am awake at night thinking about the waste sensors (wife wants immediate attention to this new glitch) .Usually starts when the tank is about 4-6 inches full or greater, ~ when level is right near 1/4 tank sensor. I cross checked all water leak points sinks, showers, toilet, washer, outside faucets and the fresh water tank no leaks from any of them. The actual leak is very small (~1/2 cup) every 15 min or so. Spawns a slow dripping from water bay (yep stinky water too). No leak when I leave waste drain open. Read some blogs and talked to Newell tech's. The suspect is one of the sensors possibly leaking. I have yet to see an actual leak (but using towels isolated it to the waste tanks bottom right below the sensor. I will look closer when i take of the covering, but the 1/4 full sensor is looking like the culprit.
My question, For short term fix would it be feasible to patch the sensor area (thinking all of them) with a rubber sealant. I figured it's not under too much pressure and we only usually fill our tank about 1/2 before dumping. Was concerned about using rubber around the sensor.

[LynnJeff]

We switched to Garnet industries gagues on the outside of all the tanks including fuel

Has worked perfectly for past 7 years no issues

Garnetindustries.com

Granbury Texas

[rheavn]

Here is the right link.

https://www.garnetinstruments.com/rv-shop/

[Richard]

Post a picture please.

You will find patching any kind of leak from the outside is usually ineffective. Plus the tank material is polyethylene which is almost impossible to achieve to a good bond with any kind of caulk, adhesive, or epoxy.

First, get a roll of the blue paper towels used for the shop. One drop of water turns dark blue on that towel. Then using the knowledge that water does not run uphill, strategically place the towels to locate the drip.

If it is a leaking sensor, follow the instructions in the beginning of the thread to fix. It really is a piece of cake.

After you post a pic, I will send an Amazon link to the replacement sensors, once I am sure they are one and the same.

[folivier]

If it's the tank itself leaking it might be possible to get it plastic welded. Basically you need a piece of the same plastic and use a hot air welder to weld it. That's all I know is what I've read.

[Guy]

Our coach, being much older than 431 has little in common with black water tank design, but we nearly removed a tank that we were sure was leaking when it has a few inches of liquid in it. I always have to remember Richards, "look for the simple first" mantra. Liquid was coming out from under the tank, but the slow ( 1 cup per hour) stopped with the dump gate valve in the open position. After wraping different components with blue paper towels. we found that the 3" dump vavle on the drivers side had a leak around the operating shaft. It would wick down the abs drain pipe, and drip off the bottom of the tank, out of our line of sight. 

I don't know if any of this applies to the design of your newer coach.