Fixing / Replacing holding tank sender

[Rohan]

Wondering if this is worth my trouble or I should leave it alone.

Both the senders in my water tank & holding tank don't work properly. The water tank one looks like a very easy and straightforward replacement.

The holding tank though is a different story. Not surprisingly it has a lot of sealant over it. I can cut through that, but frankly I am not relishing the idea of opening up a holding tank. I can pump it out and rinse it out but still it seems like a pretty unpleasant job. I would really like to fix this sender but I can live without it if need be.

It's not entirely non-functional, but it's strange, when the holding tank is full, the needle will jump to full. But it won't register anything at all otherwise. Anyone have experience with this?

It's a 30 gal holding tank and a WEMA QC-5 sender if that matters.

[S/V Illusion]

To state the obvious, having a working tank monitor can be useful so I’d get it working but, just as I wouldn’t clean out a septic tank in the back yard, I wouldn’t work on a holding tank myself. Stimulate the economy and have the yard guys do it.

[peghall]

Easiest least expensive solution: replace both tank monitors with a system that uses sensors that attach to the outside of the tank. SCAD is top rated by Practical Sailor and offers a 2 tank system. Scad Tank Monitors



--Peggie

[Rohan]

Originally Posted by peghall

Easiest least expensive solution: replace both tank monitors with a system that uses sensors that attach to the outside of the tank. SCAD is top rated by Practical Sailor and offers a 2 tank system. Scad Tank Monitors

Thanks! I'll look into that. I wonder how accurate they are. I prefer gauges with needles but still this might be a solution.

[Rohan]

Originally Posted by S/V Illusion

Stimulate the economy and have the yard guys do it.

Unfortunately in my local area, there aren't many of those kinds of guys and right now they are backed up for a very long time.

[Bill Seal]

WEMA tank senders are just a string of resisters and reed switches inside a s/s tube, activated by a floating magnet on the outside of the tube. There's probably a broken connection inside the tube.
Just beware, acccording to California's silly Prop 65, eating the sensor could cause cancer.
This item may be known to the State of California to cause cancer, birth defects, or other reproductive harm. Just another reason California voters shouldn't be allowed within a mile of a ballot box.

[ranger58sb]

Originally Posted by Rohan

It's not entirely non-functional, but it's strange, when the holding tank is full, the needle will jump to full. But it won't register anything at all otherwise. Anyone have experience with this?

It's a 30 gal holding tank and a WEMA QC-5 sender if that matters.

Sometimes the float gets stuck... and then gets unstuck... and that might especially be the case if it's their much older plastic unit.

Anyway, WEMA's (KUS') newer stainless holding tank senders wouldn't be mounted with a lot of interfering sealant. They have a collar which attaches to the tank... and then the sender assembly itself just screws into the collar. And easily screws out for occasional cleaning. Check out the KUS website, if what I'm describing sounds different from what you have.

-Chris

[Dave Lochner]

Originally Posted by ranger42c

Sometimes the float gets stuck... and then gets unstuck... and that might especially be the case if it's their much older plastic unit.

Anyway, WEMA's (KUS') newer stainless holding tank senders wouldn't be mounted with a lot of interfering sealant. They have a collar which attaches to the tank... and then the sender assembly itself just screws into the collar. And easily screws out for occasional cleaning. Check out the KUS website, if what I'm describing sounds different from what you have.

-Chris

At the bottom of the Kus/Wema holding tank sensor is a spring clip. Release the clip and the outer tube comes off for cleaning. There is probably some crud on the sender that is hangin up the float.

https://kus-usa.com/product/holding-...nder-shs-shst/

[bobgarrett]

I never had a holding tank level sensor but wanted one. I feared all the issue with fitting something in that "pit", and how long it would be before it seized up and needed cleaning. There are commercial kits that sense the level from outside but they are quite pricey and I also saw some poor reports.
I bought three of these https://www.ebay.co.uk/itm/Non-Conta...72.m2749.l2649
or something similar.
With 12v to them and a little adjustment they light up when the "fluid" is level with them and can also drive remote leds if you don't have a holding tank level view port.

[Davidhoy]

I may be somewhat biased, since I work for the company, but I really love my Maretron TLM100 ultrasonic level sensors. A while back I replaced all my old resistive fuel level sensors, and just today got new sensors for all my fresh water tanks. You do have to remove the old sensors and attach the new ones to the top of the tank - not the most pleasant task with a black water tank, but not nearly as gross as unclogging a tank that's too full ;-)

-David

[Davidhoy]

Originally Posted by Bill Seal

WEMA tank senders are just a string of resisters and reed switches inside a s/s tube, activated by a floating magnet on the outside of the tube. There's probably a broken connection inside the tube.
Just beware, acccording to California's silly Prop 65, eating the sensor could cause cancer.
This item may be known to the State of California to cause cancer, birth defects, or other reproductive harm. Just another reason California voters shouldn't be allowed within a mile of a ballot box.

I doubt that there is a single marine product that is not caught up in that Prop 65 net. It's utterly ridiculous!

-David

[Flatswing]

[QUOTE=Rohan;3375613]Wondering if this is worth my trouble or I should leave it alone.

The holding tank though is a different story. Not surprisingly it has a lot of sealant over it. I can cut through that, but frankly I am not relishing the idea of opening up a holding tank. I can pump it out and rinse it out but still it seems like a pretty unpleasant job. I would really like to fix this sender but I can live without it if need be. “

That’s just silly. First, tough to beat Peggy’s advice re: replacement. Second, you need to find out why it’s gooped up with sealant. Marine heads are one of the number one issues cruising so might as well dive in. Flush multiple times, lots of Chlorox, protective gear & trash bags. Get it apart, clean up/replace the sender or convert to an access hatch if adopting Pegggy’s on tank solution. Most senders get blocked with animal fat in the waste or crusted with crystals from pee. Phosphoric acid works best for the crystals.
Knowing the ins & outs of your black water system is valuable information. I disassemble & clean my sender every 12-18 months - well worth it. Much easier now I have a disconnect plug allowing it to be easily removed for cleaning. Takes 30 minutes now.

[Rohan]

Originally Posted by Flatswing

Second, you need to find out why it’s gooped up with sealant. ...
Knowing the ins & outs of your black water system is valuable information. I disassemble & clean my sender every 12-18 months - well worth it. Much easier now I have a disconnect plug allowing it to be easily removed for cleaning. Takes 30 minutes now.

The sender is mounted on the tank, and the sealant covers the top of the sender, I assume to prevent smell or leakage. It's not blocking the plumbing or anything.

If you open up your holding tank very 12-18 months, you are a braver man than I. Maybe I'll get a gas mask and just do it. I may be imagining it a lot worse than it really is.

[Flatswing]

Originally Posted by Rohan

The sender is mounted on the tank, and the sealant covers the top of the sender, I assume to prevent smell or leakage. It's not blocking the plumbing or anything.

If you open up your holding tank very 12-18 months, you are a braver man than I. Maybe I'll get a gas mask and just do it. I may be imagining it a lot worse than it really is.

Well like most things, once you get started - it's never as bad as one fears. Though the job always takes twice as long 'cause you find more stuff to fix, but it is well worth it. Seriously though, the goop on the sender fitting is probably to prevent seepage or smells. Why was this a problem? A corroded fitting is one possibility - which needs replacing - Peggy Hall has lots of ideas for those.
A blocked vent can put pressure on the sender tank fitting seal causing bad smells in the boat. Peggy will tell you that the commonest cause of a blocked vent is at the thru hull fitting - mud daubers especially.
Usually any liquid overflow around the sending unit came from an over filled tank ('cause the gauge was broken-which is why you should fix it!) resulting in sewage slopping into or backing up into the (frequently 90 deg.) fitting on top of the tank that the vent hose connects to. Plan on also pulling the vent hose off the tank fitting and inspecting both sides carefully for partial or complete blockage.