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Holding tank sender replacement

Tim22

.
Jun 16, 2014
238
Hunter 310 Ottawa
The sending unit in my holding tank has become clogged and it is time to replace it - o joy! I am planning on replacing it with a Scad internal unit which uses a one inch npt threaded hole. I am trying to figure out what the current install configuration is and how best to remove it and install the new one. I have attached a photo of the current installation. Any suggestion?
Thanks
Tim
 

Attachments

Tim22

.
Jun 16, 2014
238
Hunter 310 Ottawa
Unfortunately I can’t install the exterior mount sender as the tank tapers to 5 inches at the bottom and doesn’t get wide enough to install the two sensor tapes until about half way up the tank. To complicate further I only have access to one end of the tank and the location of the fittings make it impossible to run the tapes So short of removing and re installing the tank the exterior mount isn’t going to work. I replaced the old tank five years ago and there is no way I am removing and installing again - not ever!

Tim
 
Jan 11, 2014
7,373
Sabre 362 113 Fair Haven, NY
That looks like a Kus unit. It should unscrew from the tank with a 1 ½" thread. Once you pull it out there is a spring clip at the bottom that will allow the shield to be removed. Remove the shield clean it up and put it back in.

It is a really well built sensor. I wouldn't replace it.

 
  • Like
Likes: rgranger
Dec 2, 1997
7,963
- - LIttle Rock
I second Dave's advice. Cleaning internal sensor units isn't a fun job, but it's actually fairly easy. Body waste is full of animal fats...that's what's clogging the sensors, so you need a good grease cutter. Step 1. Put it in bucket of water to which you've added at least a pint of detergent......an engine degreaser works best. Let it soak for at least a couple of hours.

Step 2. Remove it from the bucket. If you're lucky and used enough degreaser, you may be able to blast what's left off it with a hose..better yet, a power washer--carefully! If it's stubborn, you may have to scrub with a brush..NOT a wire brush...that'll scratch it...a tooth brush to get into tight places, a scrub brush where that'll work.

PLAN B: Before cleaning or using a SCAD internal sender, give 'em a call to discuss whether you really can't use the external strips....whether they really have to go all the way to the bottom, how far apart they need to be. These are questions I need to ask 'em too!

--Peggie
 
Jan 4, 2006
3,640
Hunter 310 West Vancouver, B.C.
Hey Tim,

No reason you can't install an external sensor same as mine as I believe our boats are the
same year.

Holding Tank Dimensions.jpg


Sensor Location on Holding Tank.JPG



I replaced the old tank five years ago and there is no way I am removing and installing again - not ever!

Aw, c'mon .................... it's kind of fun after a while specially when it's up to your armpits. Admit it, now :poop:.
 
Oct 22, 2014
14,956
CAL 35 Cruiser moored EVERETT WA
Of you really need to know, using a gauge, when the waste tank is empty?

It seems to me the goal is to be able to tell when the tank is 2/3rds or more full.

I’m interested in what Scad has to say.When I installed the sensors on my tank I had to cut the foil strip down so that it did not extend beyond the tank. I know it does Not extend to the bottom of the tank. It does extend to nearly the top. I figure when the tank gauge reads full there are a couple of inches left. I do not want it backing up so I empty before it over fills.

The question is there a minimal length required of the sending unit to provide a signal to the gauge.
 
Jan 11, 2014
7,373
Sabre 362 113 Fair Haven, NY
The Kus (formerly Wema) gauge is a high quality gauge with few moving parts. The rod has a series of magnetic reed switches that change the resistance as the float moves. There is enough play in the float that it will be difficult to clog up. The liquid and the waste senders are basically the same and are available with different mounting options. The waste ones have a standard NPT thread and the rod is protected by a SS tube to help keep stuff out. I'll be installing one this spring and using a tank sensor module to change the output to NMEA 2000



IMG_0187.jpeg

IMG_0185.jpeg
 
Oct 22, 2014
14,956
CAL 35 Cruiser moored EVERETT WA
As a Float tube design, it is a good as it gets.

I have the WEMA float in my Starboard Tank when the original sender (1974 vintage) failed.. The WEMA has shown to be accurate and reliable over the past 3 years on my boat. I would expect their waste tank sender to be the same.