Holding Tank: Choice of Level Sender Unit

[Sealong]

Hello, I am fitting a gravity-discharge holding tank to my boat (with deck pump out, diverter valve etc.). The tank can only fit in one place and that location has limited access above it; enough to access the plumbing but not enough to remove, for maintenance, a 400mm length of float-type sender (e.g. TankMinder 1, 3 and SH3). The obvious alternative is the ultrasonic sender BEP Marine TS1 or the non-invasive SCAD TM1.

I would like to hear from anyone who has experience of using a non float-type sender unit in a black waste tank and any recommendations they may want to pass on.
Thanks in advance
Christopher

 

[vyv_cox]

For the cheapest and simplest method of determining tank depth, see towards the bottom of this page Toilets, holding tanks and associated matters

 

[Sealong]

For the cheapest and simplest method of determining tank depth, see towards the bottom of this page Toilets, holding tanks and associated matters

vyv_cox, many thanks. You have just saved me around £200. I like your simple and cheap idea and it makes perfect sense. If the reliability of tank senders is questionable, then a visual check will always be necessary. So forget the sender and gauge and use a torch.

 

[Aquanaught]

Alternatively fit a 12v LED light tape vertically to the rear of the tank connected by a momentary push switch. Only works though with the clear type plastic tanks. When we changed boats and had a black tank I fitted a Gobius unit which works well. Gobius 4 for grey, black & waste tanks - Gobius

 

[melvynpatrick]

You could fit a gobious pro. I have two. They fit outside the tank so don’t get covered in you know what. Not cheap. But good

 

[Mistroma]

Alternatively fit a 12v LED light tape vertically to the rear of the tank connected by a momentary push switch. Only works though with the clear type plastic tanks. When we changed boats and had a black tank I fitted a Gobius unit which works well. Gobius 4 for grey, black & waste tanks - Gobius

I bought a very cheap flat LED patch years ago in Spain and fixed it to the rear of the tank. There was power next to it for an optional cooling fan and I only needed a simple switch. It worked perfectly and you can always see the dark shadow clearly indicating the level. Dirt cheap, accurate and reliable.

I was thinking about some DIY sensors and ESP32 before realising the tank was sufficiently translucent.

 

[riverliver]

The gobius 4 will only work on a vertical tank not one laid horizontal (I bought one here and never fitted if anyone wants one). Now bought a gobius pro which I hope might work but fitting it over winter so cant say yet

 

[wonkywinch]

Another vote for the Gobius, easy to fit and seems quite accurate ( I tested it by pouring 20 litres of water at a time into the 80 litre black water tank it monitors).

 

[rogerthebodger]

with a holding tank I simply have a float switch mounted in the top of the tank to show when the tank is full and need emptying

 

[Sealong]

with a holding tank I simply have a float switch mounted in the top of the tank to show when the tank is full and need emptying

Yes and the simplicity of that item would probably be my first choice. However, as I mentioned, my particular problem is lack of clearance above the tank to remove a float-based unit for maintenance.

 

[trbt]

For DIY route there is a cheap (~13 eur) XKC-DS1603 ultrasonic liquid level sensor, that is attached (glued) to the bottom of the tank and reports liquid level over TTL serial, RS485 or as analog voltage. This works very well in my testing (yet to be put on the boat), also there are existing projects on the web for integrating this to SignalK, for example Ultraschall Tanksensor mit SensESP – open-boat-projects.org

 

[melvynpatrick]

I have a mopeka pro on my diesel and water tanks. A similar thing I think