Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 26-07-2020, 19:30   #1
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: Adelaide, South Australia
Boat: Swanson 42
Posts: 7,006
Looking at doing a DIY capacitive black water tank sensor

Hi all,

I am getting a little tired of playing the "guess the blackwater tank level" game, even more tired of getting it wrong.

I've looked at some of the options for monitoring the level, and the one that looks like it will work best with my particular setup is a capacitive sensor.

There are many good articles on DIY capacitive tank sensors, but most are for somewhat "cleaner" environments than a blackwater tank.

I am curious to see if anyone is using a submerged capactive sensor for their tank, and if so, how does it perform over time? Does it block up in any way (no need to go into horrible details here), has it proved reliable over time?

If you went DIY, which approach did you take with the construction?


Edit: I am not entirely settled on a submersible capacitance sensor. I will try external sensing (timber and fibreglass tank), but it seems from some reading here on CF that the external sort get into trouble from the walls of the tanks become... er... messy.

Thoughts and experience of the external sort, particularly DIY would also be helpful.


Matt
__________________
Launch delayed.
GILow is offline   Reply With Quote
Old 26-07-2020, 20:12   #2
Registered User
 
wefleenor's Avatar

Join Date: Nov 2010
Location: Portland, OR
Boat: 49ft custom power catamaran
Posts: 51
Re: Looking at doing a DIY capacitive black water tank sensor

Yes, I have units that fit into a pvc tube and stick down into the black water tank. I have issues with them fouling and giving poor readings. Good news is they function well near the top. However, I am now working on an ultrasonic sensor attached to a pi to measure the level.

Bill
Double-Wide
wefleenor is offline   Reply With Quote
Old 26-07-2020, 20:22   #3
Registered User
 
chrisr's Avatar

Join Date: Dec 2016
Location: Australia
Boat: Tasman 40' catamaran
Posts: 694
Re: Looking at doing a DIY capacitive black water tank sensor

why does the mix of 'DIY' and 'black water' send shivers down my spine ?



cheers,
__________________
"home is where the anchor drops"...parked on mooring at Yamba for a few weeks while we visit family in Newcastle & Sydney... maintaining social distancing !
chrisr is offline   Reply With Quote
Old 26-07-2020, 21:07   #4
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: Adelaide, South Australia
Boat: Swanson 42
Posts: 7,006
Re: Looking at doing a DIY capacitive black water tank sensor

Quote:
Originally Posted by wefleenor View Post
Yes, I have units that fit into a pvc tube and stick down into the black water tank. I have issues with them fouling and giving poor readings. Good news is they function well near the top.


Hmmm... I feared this would be an issue. Do you think the dielectric gap has an influence on the probability of fouling or is it simply stuff adhering to the electrodes?

Did you try the external sensor approach?

Ill be interested to hear how your ultrasonic sensor works out. It was my preferred approach initially, but it seems there can be problems with the surface being a little... err... fluffy from time to time and preventing a good reading. Also lots of complaints about needing to clean the sensors, even though they are not submerged.
__________________
Launch delayed.
GILow is offline   Reply With Quote
Old 26-07-2020, 21:09   #5
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: Adelaide, South Australia
Boat: Swanson 42
Posts: 7,006
Re: Looking at doing a DIY capacitive black water tank sensor

Quote:
Originally Posted by chrisr View Post
why does the mix of 'DIY' and 'black water' send shivers down my spine ?







cheers,


Yeah, some room for trouble, no doubt about that.

Touch wood, no major problems with my DIY holding tank so far (less than a year), aside from keeping track of the capacity remaining.
__________________
Launch delayed.
GILow is offline   Reply With Quote
Old 26-07-2020, 22:00   #6
Registered User
 
chrisr's Avatar

Join Date: Dec 2016
Location: Australia
Boat: Tasman 40' catamaran
Posts: 694
Re: Looking at doing a DIY capacitive black water tank sensor

can you see the tank easily ? is there room for an external sight glass - or even a translucent panel in the tank

would have the added advantage of seeing what you had for dinner last night...



cheers,
__________________
"home is where the anchor drops"...parked on mooring at Yamba for a few weeks while we visit family in Newcastle & Sydney... maintaining social distancing !
chrisr is offline   Reply With Quote
Old 26-07-2020, 22:20   #7
Registered User

Join Date: Apr 2007
Location: Australia
Boat: Island Packet 40
Posts: 4,022
Images: 7
Re: Looking at doing a DIY capacitive black water tank sensor

Have a look at Jaycar Cat ZD1904, let your imagination loose and see what happens.
RaymondR is online now   Reply With Quote
Old 26-07-2020, 23:08   #8
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: Adelaide, South Australia
Boat: Swanson 42
Posts: 7,006
Looking at doing a DIY capacitive black water tank sensor

Quote:
Originally Posted by RaymondR View Post
Have a look at Jaycar Cat ZD1904, let your imagination loose and see what happens.


That would be a good option if I had an outlet at the bottom of the tank, but I dont, and for fairly obvious reasons Im kind of reluctant to start drilling holes.

Ive see the approach of using a pressure sensor combined with a dip tube with an opening at the bottom, but in most cases it seemed it was hard to maintain pressure over time, so the readings become increasingly inaccurate, just when youd really rather they were not.
__________________
Launch delayed.
GILow is offline   Reply With Quote
Old 26-07-2020, 23:10   #9
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: Adelaide, South Australia
Boat: Swanson 42
Posts: 7,006
Re: Looking at doing a DIY capacitive black water tank sensor

Quote:
Originally Posted by chrisr View Post
can you see the tank easily ? is there room for an external sight glass - or even a translucent panel in the tank



would have the added advantage of seeing what you had for dinner last night...







cheers,


I cant find the vomit emoticon, darn it.

Although access to the tank is very good on three of the four sides, I think Ill give that approach a miss.
__________________
Launch delayed.
GILow is offline   Reply With Quote
Old 27-07-2020, 02:14   #10
Registered User

Join Date: Apr 2007
Location: Australia
Boat: Island Packet 40
Posts: 4,022
Images: 7
Re: Looking at doing a DIY capacitive black water tank sensor

Quote:
Originally Posted by GILow View Post
That would be a good option if I had an outlet at the bottom of the tank, but I dont, and for fairly obvious reasons Im kind of reluctant to start drilling holes.

Ive see the approach of using a pressure sensor combined with a dip tube with an opening at the bottom, but in most cases it seemed it was hard to maintain pressure over time, so the readings become increasingly inaccurate, just when youd really rather they were not.
You could put a sounding tube in from the top and have one of those things they use to pressure up the blood pressure cuff to pump air in and have a calibrated U tube full of water to read off the depth. Or use the pressure transducer and a meter.
RaymondR is online now   Reply With Quote
Old 27-07-2020, 06:53   #11
Registered User
 
AKA-None's Avatar

Join Date: Oct 2013
Location: Lake City MN
Boat: C&C 27 Mk III
Posts: 1,062
Re: Looking at doing a DIY capacitive black water tank sensor

Ive thought of possibly adding Some way of flushing fresh water down past the electrodes not sure how that would work but a thought
__________________
Special knowledge can be a terrible disadvantage if it leads you too far along a path that you cannot explain anymore.
Frank Herbert 'Dune'
AKA-None is offline   Reply With Quote
Old 27-07-2020, 06:57   #12
Registered User

Join Date: Jun 2019
Location: Rochester, NY
Boat: Chris Craft Catalina 381
Posts: 1,179
Re: Looking at doing a DIY capacitive black water tank sensor

I haven't messed with a capacitive sensor for black water, but I've got the Blue Sea ultrasonic sensor in my tank and it's been pretty good. Occasionally it'll seem to lose reading or get a bit funky, but it's only happened twice and both times has self-resolved fairly quickly, so I'm not sure what's causing it. The rest of the time, it's very accurate (when compared to visually looking at the slightly translucent plastic tank).
rslifkin is offline   Reply With Quote
Old 27-07-2020, 08:48   #13
Registered User

Join Date: Oct 2015
Posts: 9
Re: Looking at doing a DIY capacitive black water tank sensor

I have been looking at this Gobius Pro, Bluetooth Level Indicator, Marine Sanitation in Wash state carries them, but have not made the jump. My thought was try one at the top of my tank so that it would alarm when 75% full. Anyone else used them?
Miket99 is offline   Reply With Quote
Old 27-07-2020, 10:49   #14
Registered User
 
John De Bree's Avatar

Join Date: Jul 2020
Posts: 9
Re: Looking at doing a DIY capacitive black water tank sensor

I used on my old boat a float switch off a submersible septic pump and it worked well. Never had a problem with it.
John De Bree is offline   Reply With Quote
Old 27-07-2020, 11:04   #15
Registered User
 
wefleenor's Avatar

Join Date: Nov 2010
Location: Portland, OR
Boat: 49ft custom power catamaran
Posts: 51
Re: Looking at doing a DIY capacitive black water tank sensor

Quote:
Originally Posted by GILow View Post
Hmmm... I feared this would be an issue.

Did you try the external sensor approach?

.
Stuff adheres to the outside of the pvc tube, not directly to the sensor material, but it does change the readings.

I do not have access to the outside of the tank, only the top.

I have a PhD in environmental engineering so I have little fear of my ability to properly handle wastewater. My years of academic research included the development and use of many electronic sensors, including ultrasonic. I have built and resurrected toilets in several developing countries during 12 years as adviser to the Engineers Without Borders chapter.

In this case I am simply accessing the top of the tank through an existing access plate that provides the vent and will actually leave a bit of an air gap from the max fluid level to the ultrasonic sensor to minimize fouling.

Bill
Double-Wide
wefleenor is offline   Reply With Quote
Reply

Tags
DIY, water

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fresh Water, Gray Water and Black Water Holding Tanks vweber Plumbing Systems and Fixtures 10 13-07-2018 20:25
Salt Sailing & DIY Interior Projects are doing a New Years Giveaway :) SSG2015 Multihull Sailboats 1 21-12-2015 06:52
Ultra sound water tank sensor landonshaw Construction, Maintenance & Refit 10 29-07-2014 17:02

Advertise Here


All times are GMT -7. The time now is 01:49.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.