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oak_box 06-22-2021 11:36 AM

Water tank level sensor
This weekend, I pulled out the float sensor in my water tank.

I have a metal tank, the sensor has the 5 screws around the perimeter.

The strange thing was that the screws weren't threaded into the tank itself. There is a metal ring with threaded holes on the inside of the tank, basically clamping the sending unit to the tank. I was VERY lucky that one of the screws stuck, allowing me to find out that the interior supporting ring was completely separate from the tank. With most of the screws removed, I was able to carefully work the ring out (there was a notch cut in it to allow it to get through the hole in the tank).

Has anyone seen this before? Or do most cases just drill holes in the tank, secure with self tapping screws, and call it a day?

It looks like there was some sort of anti-seize compound on the screw threads, possibly to keep them from backing out, more likely to keep them from corroding - I was fairly shocked to be able to get the screws out after 40 years!

I'm assuming I should use anti-seize when I put in the new sensor. What compound is SAFE to use in a water tank? (or is there such a thing?) I had to use a little PB-Blaster to get the screws loose, and I'm sure there was some amount of dirt/debris that fell into the tank. So I won't be DRINKING the water any time soon. But eventually, it would be nice if I could flush the tank enough to be able to trust the water for drinking. For now, I'll just use it for washing.

Turtle Blues 06-22-2021 12:14 PM

Standard installation for most Taiwanese metal water and fuel tanks that I see. Units are usually mounted on the access port cover which is safer to remove as the studs are usually welded.
I would cover the nut and tip of the bolt with a dab of silicone rather that other chemicals to keep from contaminating the water.

oak_box 06-24-2021 11:24 PM

I hadn't considered the fuel tanks - but you're probably right that they are most likely a similar setup.

I'm assuming regular automotive anti-seize is the right thing to use on the screws for the fuel tank sending units?


Turtle Blues 06-25-2021 05:56 AM

Can't hurt, but my preference would be a fuel rated thread sealant.

ranger42c 06-25-2021 06:53 AM

That sounds vaguely like approx. half of the WEMA/KUS holding tank sensor assembly.

In their units, there's a horseshoe-like fitting that goes inside the tank, and a full circle fitting that screws to that horseshoe.

But that assembly is also center-threaded and the actual sensor itself screws into the now-already-fitted mounting assembly.

I think they make the same mounting system for their freshwater tank sensors, too.

I mention it because if the screw pattern might match, or even if it doesn't, swapping to the WEMA/KUS set-up might be (relatively) easily possible and you wouldn't need much in the way of caulk or sealant.


Codger2 06-25-2021 08:46 AM

3 Attachment(s)

Originally Posted by oak_box (Post 1014449)
Has anyone seen this before? Or do most cases just drill holes in the tank, secure with self tapping screws, and call it a day?

That's exactly what I did just a few weeks ago & it was in complete agreement with the instructions. My water tank is plastic however.

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