Waste tank sensor

[Midnightsun]

OK so heres the deal, decided to get a head start on the project and went through my overstock of boat parts and aquarium parts. Turns out I have a virgin cap and a bulkhead fitting waiting to be used.

The Tank watch system uses a large standard 3" cap which holds the 3 probes. This is easily removed by unscrewing the entire assembly.

Probes......https://www.seleneoceanyachts.com/wp-co ... system.pdf

New Cap.....https://marinesan.com/3-cap-w-o-ring/

Wanted to just drill and tap the virgin cap but the material is rather thin so I went with a bulkhead fitting that has a 1" NPT thread, same as the SCAD probe so it will be an easy install.

Plan is to make an adapter plate to replace existing tank watch gauge and use the existing wiring. Will add to this as I get parts.

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[pepmyster]

WoW!!!! Just wow!!!! Nice work, as usual.

[vineyardgray]

I abhor the idea of opening my poo tank for any reason so since my boat never came with any of those fancy high falootin' tank monitors I have been entertaining the following system. Regrets to those who have opened their tanks. Or perhaps congratulations
https://www.gobius.se/en/products/level-indicator-for-boats/

[Midnightsun]

A small update.

Got my SCAD TM1 unit. Was pleasantly surprised to see how small it is. 2" x 2" x 1/4" thick. Made to be surface mounted with the supplied 4 small black screws. A small hole will need to be drilled to accommodate the plug in wiring on the back side which is rather simple.

The white tube is the screw in sender which will need to be cut to the correct length of my holding tank depth. Ideally it should be almost touching the bottom of the tank when screwed into place.

Will update in spring after install and calibration but this really looks promising.

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[pepmyster]

Very nice Hans, very nice!

[Midnightsun]

Just to elaborate on the sender. This type is basically the same as using those stick on metal strips to the exterior of the tank however with a twist to make it suitable for metal tanks where strips do not work or in my case where I have minimal access to the sides of the tank.

In the picture below showing the bottom of the probe you can see the 2 copper strips. Cut to length on a table saw and then the supplied cap is glued in place with pvc cement. In the end it gives you a reliable, foul proof sender which is the biggest issue on holding tank units.

Every place I have seen these units for sale come standard with the tape on senders. The internal type shown is always an extra order item for at least an additional $70. There is one exception which is where I bought mine and for the same price as the scad TM1 you can choose your sender type which equates to at least a $70 savings not to mention their price was the lowest I could find. Choose the option "internal for metal tank" https://www.sailorssolutions.com/?page= ... s&Item=TM1

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[Midnightsun]

Made an adapter plate today from a piece of left over acrylic. Same size and hole pattern as the existing tankwatch4 panel which it will replace. Elected to use VHB tape to secure the gauge to the acrylic as opposed to the supplied screws. Plan is to install it in the same location as the old unit utilizing the same screws. All wires needed and then some are already there and go to the original sender so using those will make the entire installation rather easy.

I could have made this prettier but it does go inside the medicine cabinet in the aft head and is only visible by opening the cabinet door. Bottom line is it is hidden for just my wife and I to look at as required.

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[Midnightsun]

This project has been a nightmare because the Scad unit simply does not work. Everything is installed and programmed multiple times even with help from Scad as a last resort. The unit must be defective but honestly after going through all this I am not convinced as to the reliability/accuracy of the electronics/sender style. I should mention years ago I had a unit made by Snake river which I believe were the original ones that used those copper strips located on the side of the tank. I did have to recalibrate every so often on that unit and then after a few years the gauge portion just gave up. It was replaced however it also failed after a few years. Figured they must have worked out the bugs by now but obviously not.

Plan B

Will be installing a trusty float sender that always works. Have decided to go with this one as it can be easily removed and the unit has a snap ring on the bottom to take the sender out of the external casing to clean which is a requirement on a black water tank internal float sender. Used the 0-190 ohm unit. https://www.aliexpress.com/item/4001053 ... 1802jbIB7I

Will use this new gauge by Bluesea, compact and small.
https://www.bluesea.com/products/1739200/Mini_OLED_Tank_Meter_-_Blue

Will report back in a month or so with results however I am confident this will work as intended.

[Midnightsun]

Will be installing in the next couple of days. Bench tested all and works like a charm. Clear and easy to read gauge lit at all times for easy viewing with a resolution of 5% digital increments along with a bar graph.

Used the same poly inspection cap as indicated on the first attempt to avoid piercing the tank. Needed a 1 1/2" BSP bulkhead fitting since the senders sold on Aliexpress all seem to be this thread style. The DN32 is the correct one. https://www.aliexpress.com/item/1005002 ... 1802eeQ8an

Soldered on a quick disconnect plug to the sender wires so the unit can easily be unscrewed and cleaned outside of the boat. As mentioned, there is a snap ring on the bottom of the sensor to allow the outer protective body to be removed for cleaning of the float if required. Really easy to unscrew by hand as there is only an o-ring seal between the sender flange and the bulkhead fitting

The Bluesea indicator is a snap to install and wire up. positive/negative and the 2 sender wires on a convenient push in plug.

Total cost for this setup was about $140 CAD.

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[pepmyster]

Too bad the other didn't work out. I found, by chance, an external sensing unit which I bought for my Rinker years ago and forgot about because we sold.(Obviously) Removed the old monitor and installed exterior sensors. Sensa Tank 2 is what I installed. Works great and I don't have to clean the sensor anymore. I am very surprised your mod didn't work but you always have a plan B.