Portable/battery-powered External Holding Tank Monitor?

[AlastairLC]

I’m looking for an external holding tank monitor that doesn’t require wiring. I found this
TouchSensor 100600442-01 SensaLevel Ultra Single Sensor Amazon.com: TouchSensor 100600442-01 SensaLevel Ultra Single Sensor: Automotive
but it doesn’t say what powers it and the wires look suspicious.
Has anyone found such an item that could be used to occasionally check waste level? (All I need.)

 

[Rich Stidger]

It must have power so I suspect that it uses 12V. Hence the in-line fuse holder. These type of sensors do not work on metal holding tanks. And if your tank is a poly tank and you have a spot to hold this sensor, then I would think that you could see the level thru the tank. In my experience, holding tank sensors are problematic at best. At worst, they simply don't work.

 

[AlastairLC]

Thanks Rich. My tank is poly, but I can’t see through it even when I put a flashlight against it.

 

[Rich Stidger]

I have a Snake River brand of capacitance sensing holding tank gauge and it simply doesn't work. I have sent the display unit back to them and they have told me that it works fine. The sensor I have is an in-the-tank PVC rod and it also outputs a change in voltage with tank level. But the system just doesn't work. I have given up on it.
I know that our holding tank capacity is good for 8-9 person-days before needing to be emptied. So if there are 2 people on board, that is 4 days. 3 people is 3 days. I mark the pumpouts on a calendar with the TOD it was pumped.

 

[AlastairLC]

Same here. I keep track of usage and pump out after a certain number, but it would nice to have a fallback. (In case I lose count.)
But it would have to be external.

 

[tfox2069]

If it has to be battery powered, you're extremely limited to probably some rare industrial applications, like this one, but you'll have to contact the manufacturer for pricing - likely expensive:

ViewSonic Ultrasonic Level Sensor Transmitter

Viewsonic Series Battery Operated Ultrasonic Level Sensor has a range of 200 feet. It features an all plastic design and 1% accuracy.

iconprocon.com

If you could tap into 12v anywhere nearby, your options would include this:

Pro Wireless Tank Monitoring System | West Marine

Check out our Pro Wireless Tank Monitoring System and more from West Marine!

www.westmarine.com

I just wired one and it was super easy to install and calibrate. You check it via Bluetooth, or it comes with a simple wired remote display with a green or red light, which is programmable via Bluetooth. I opted for just one sensor, which I put at 2/3 full, so when the light turns red I know I have 1/3 of tank capacity left, and its time to pump out.

Yeah, I know - the price - but I had disconnected and disposed of my macerator and had the 12v wires right there, and didn't want to run the 3rd wire thru the boat, which is required for the nice and inexpensive external strip sensors (which are what most people run).

 

[AlastairLC]

Thanks tfox2069. Unfortunately I don’t have room between the tank side and bulkhead for anything larger than a strip.

 

[Rich Stidger]

Here is an update on the capacitance sensor that I have. It is true that this system has not worked well for the last 10 years. But this post got me thinking and since I had some time at anchor, I figured I would take another go at it.
My display was always stuck at whatever I last calibrated- either empty or full. So I pulled the PVC rod sensor with the intent to measure the voltage difference between empty and full (using a bucket with seawater). I was surprised to find out that the rod would barely pull out of the threaded hole in the top of the tank. It was coated about 1/4" with solids. So I am thinking now that the coating of solids was causing the sensor probe to sense the coating and never sense the actual level in the tank.

After cleaning and testing, I found that the output voltage of the sensor varied from 0.59V in air (empty) to 1.75V when immersed in seawater to the bottom of the threads. So now I know the sensor is working. I re-calibrated the display for empty and full and then tested the sensor at different depths in a bucket. It was not perfectly linear, but my tank is not uniform either, but it did display from empty to full according to the depth of the water.

So I inserted the sensor back into the tank and reconnected the three wires. Over the next few days I will be able to see if this is now working and I will post my results.

Seeing all of the build-up on the PVC sensor rod and after I confirm that this was the operational fault, I will add cleaning of this sensor to my yearly tasks. I have never seen any instruction that claimed cleaning was required. Obviously with an external foil sensor, this cleaning does not apply.

So AlastairLC, if you can pull your tank and apply the foil sensor, you may have a nicely operating system.

 

[AlastairLC]

Glad you got it working, Rich.
That much solid coating, huh! Makes one wonder what’s building up on the inside of the tank.

 

[Rich Stidger]

Glad you got it working, Rich.
That much solid coating, huh! Makes one wonder what’s building up on the inside of the tank.

Time will tell if it is working. And yes, I am thinking about the build-up on the tank walls. But I know of no remedy.

 

[jviss]

And yes, I am thinking about the build-up on the tank walls. But I know of no remedy.

There are several holding tank rinsers on the market. They use garden hose pressure water and a water jet nozzle to rinse the tank walls after it has been pumped out.

 

[JamesG161]

I guess I am lucky that both of my Hold Tanks are below the water line of my boat.
When appropriate and we do know the tank is empty, we turn off the macerator and let the the hold tank "backfill" with seawater. It takes about 20 minutes for full tank backfill. Rinse and Repeat 2 times if we can.
_____

I pulled the PVC rod sensor

What size hole for you sensor? Mine Wema sensor has a "cage" around it to avoid the big stuff.
Jim...

 

[jviss]

I guess I am lucky that both of my Hold Tanks are below the water line of my boat.
When appropriate and we do know the tank is empty, we turn off the macerator and let the the hold tank "backfill" with seawater. It takes about 20 minutes for full tank backfill. Rinse and Repeat 2 times if we can.
_____

What size hole for you sensor? Mine Wema sensor has a "cage" around it to avoid the big stuff.
Jim...

I hope you don't do that in the harbor, or in a river. Three mile rule still applies. (Maybe the nine mile rule for you?)

 

[Rich Stidger]

I guess I am lucky that both of my Hold Tanks are below the water line of my boat.
When appropriate and we do know the tank is empty, we turn off the macerator and let the the hold tank "backfill" with seawater. It takes about 20 minutes for full tank backfill. Rinse and Repeat 2 times if we can.
_____

What size hole for you sensor? Mine Wema sensor has a "cage" around it to avoid the big stuff.
Jim...

When I had a new holding tank fabricated, I had the large hole for the WEMA sensor replaced with a 1" NPT threaded hole. The PVC rod sensor screws directly into that port. Prior to my tank replacement, I removed the WEMA sensor and fabridated a plate with a 1" NPT opening and the holes around the circumference to duplicate the WEMA attachment.

I still have the adapter plate if it would be of use to you.