Tank level sensors

[Davidhoy]

I'm installing level sensors in my diesel and water tanks, and everything was going along smoothly. I measured the depth of the tanks, found the appropriate sensors and purchased them online. Installing the diesel level sensors went off without a hitch, and I now have level information on my NMEA 2000 data bus, displayed on my Garmin MFD.

Of course nothing ever goes perfectly on boats, and when I tried to install the sensor in the water tank I found that sides of the tanks slope inward toward the centerline, and the access hole is not above the deepest part of the tank. It's not off by much, but enough that the float tube hits the side and pushes inward, making installation impossible. I looked for an alternate sensor, perhaps one using ultrasonics instead of a float, but these too require positioning over the deepest point of the tank.

Short of relocating the access hole, does anyone have a suggestion regarding a sensor that could work in this situation?

Thanks,
David.

BTW, I'm using an AlbaCombi analog-to-N2K converter to get engine and tank level data onto the NMEA 2000 data bus - very nice piece of equipment!!

[Shrew]

If if you do get one installed, the problem will be accuracy. Unless the tank is square, cylindrical or rectangular then a gauge reading half won't represent capacity. It will only reflect the height of the contents as compared to the bottom/top.

Take a conical shape. The gauge could read "1/2", however if the cone were inverted, that "1/2" reading would be significantly less on the inverted cone, than if the base were on the bottom. Thus rendering the gauge somewhat useless.

[Davidhoy]

Originally Posted by Shrew

If if you do get one installed, the problem will be accuracy. Unless the tank is square, cylindrical or rectangular then a gauge reading half won't represent capacity. It will only reflect the height of the contents as compared to the bottom/top.

Take a conical shape. The gauge could read "1/2", however if the cone were inverted, that "1/2" reading would be significantly less on the inverted cone, than if the base were on the bottom. Thus rendering the gauge somewhat useless.

You make a good point, and I had considered that. Fortunately I'm less concerned about accuracy, and more about having a general feel for the level in the tank. That way I can chastise my crew when they use too much water washing the dishes and showering . If the level drops too much I can either fill up at the dock, or run the water maker if at anchor.

-David

[Typhoon]

I had ultra sonics on my boat when I bought it , they never worked and where all corroded.
Tore it all out and put in Wema sensors , works great , no trouble at all .

Look for a new spot to put a new hole , more trouble now , less later.

Regards John Tully

[Paul Elliott]

Is the float at the end of a metal rod, or is this a tube-type sensor? If it's got a rod, you may be able to bend the rod or turn the sensor so the float drops into the deeper part of the tank. It's never going to be accurate, but you can work out a calibration scale for it. This can still be useful, even if it reads empty when the tank isn't completely dry.

[a64pilot]

The Wema sensor I have on my boat works by having a magnetic float go up and down a tube, think floating donut on a .5" tube, no arm

See here http://www.wemausa.com/sensors/cover...l#.WH_ux8s8KfA

[Davidhoy]

The senders I bought are the Wema ones with the float on a stainless tube. They work great for the two diesel tanks, couldn't be happier. The only problem is the sloping side in the water tank and the corresponding location of the 1.5" NPT threaded fitting into which I need to install it. Since the tank hole is threaded, bending the tube won't work as I have to rotate the sender to install it. Guess I could swap the sender out for one that has the SAE 5 hole flange mounting, and install an adapter...

[gulfstar37]

Wema sells an adapter plate for the 5 hole unit. It looks like a horseshoe. Use a whole saw to cut a new hole in better location. Mark and drill 5 mounting holes install horseshoe adapter through hole inside tank and install mounting machine screws into bracket sandwiching tank top between sending unit and adapter bracket. Works very well and gives something solid to screw into. Just a hint, have several extra long screws( heads cut off) to install and capture adapter bracket inside tank. Once holes line up, slide sending unit over long screws and align and install your mounting screws then remove extra long screws and replace with your shorter mounting screws.

[Davidhoy]

Originally Posted by gulfstar37

Wema sells an adapter plate for the 5 hole unit. It looks like a horseshoe. Use a whole saw to cut a new hole in better location. Mark and drill 5 mounting holes install horseshoe adapter through hole inside tank and install mounting machine screws into bracket sandwiching tank top between sending unit and adapter bracket. Works very well and gives something solid to screw into. Just a hint, have several extra long screws( heads cut off) to install and capture adapter bracket inside tank. Once holes line up, slide sending unit over long screws and align and install your mounting screws then remove extra long screws and replace with your shorter mounting screws.

How do you keep the debris out of the tank while drilling?

Actually, if you look at the picture below of the top of the tank, you can see the 1.5" NPT plug lower right, and the PVC elbow top left connects to the deck fill hose. Perhaps I could swap these two around? That would almost certainly solve my problem...

[gulfstar37]

This is water tank? Use shop vac while drilling hole or use Vaseline on drill teeth and wipe off just before drill or hole saw breaks through and put clean Vaseline back on. Will capture 98% of filings.

Swapping the fittings may also work.

Looks from photo like there us a top plate on tank that may be removable. If so new gasket or sealant will probably be needed.

[Davidhoy]

Yes, it's the water tank. If I can't switch the fittings around I'll try your trick with Vaseline or remove the plate. Would be a good opportunity to get it cleaned up too. The PO didn't seem too concerned with maintenance and cleaning.

[SailFastTri]

Originally Posted by gulfstar37

snip
Use a whole saw to cut a new hole in better location. Mark and drill 5 mounting holes install horseshoe adapter through hole inside tank and install mounting machine screws into bracket sandwichingJust a hint, have several extra long screws( heads cut off) to install and capture adapter bracket inside tank. Once holes line up, slide sending unit over long screws and align and install your mounting screws then remove extra long screws and replace with your shorter mounting screws.

That's a good tip. After I lined mine up the first time I simply used a marker pen on both the sensor head and the surrounding tank, so all I have to do when replacing is to line up the marks.

Another tip for those who need to winterize, is to use a clear (clean) suction hose added to a shop vac to suck out the tank water at end of season ( to a level below any pickup hose connections). Then use either the blower side of a (clean) shop vac or an electric inflator air pump to blow out the fresh water hoses. I think this is better than using antifreeze, and leaves no residual antifreeze taste. Been doing this for several years in New England.

[Suijin]

From the picture, I would call that whole plate with the fittings the access plate. I would take it off and definitely inspect the tank. If it's not been opened in awhile you may be a bit surprised by what you find in there, regardless of whether you've routinely been sanitizing the tank.

That would also give you the opportunity to drill and install the new sensor where you want on the plate without worrying about contaminating the tank.

[double u]

WEMA btw can make you non-linear levelsensors...

[Typhoon]

I replaced all my tanks sensors with wema's 2 water and two diesel , also added two additional pick ups and returns . That was a lot of holes . There was really no way to stop debris from getting into the tanks . I just gave up , made the mess , and cleaned the tanks afterwards . No short cuts on boats . I find they will always come back and bite you in the bum just when you are at your most vulnerable .

Regards John Tully