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Old 10-04-2007, 08:31   #1
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Tank Tender

I currently don't have any gauges for fuel, water and holding tank levels so I'm thinking of installing a Tank Tender system. Does anyone have any experience with installing and using this system? All of my tanks are irregular in shape making me wonder how acurate any system would be for measuring fluid levels. Any input would be appreciated.
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Old 10-04-2007, 08:37   #2
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How about using a dip stick with marks indicating the amount of fluid in the tanks.
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Old 10-04-2007, 08:39   #3
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The Hart Tank Tender operates on air pressure. It pumps a small amount of air through tubing to the bottom of the tank. The excess air pressure bleeds off until the air pressure in the tube equals the liquid pressure in inches of depth, to be interpreted in gallons of fuel or water (water weighs 8.35 pounds to the gallon and diesel weighs 7.18 pounds to the gallon). Accordingly, the tank shape is of no consequence whatever.
They're very accurate.
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Old 10-04-2007, 10:03   #4
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Gord,

The resultant air pressure in the Tank Tender is proportional to depth of the liquid being measured, so if it's in a tank with vertical sides, it's a good measurement of gallons left, but if the tank has tapered sides, you can only know the depth, not the volume.

Steve B.
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Old 10-04-2007, 10:15   #5
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But you can make a calibration table, just like you would for a stick. I'm considering a Tank Tender as I would have to cut another hole in my cabin sole to use the stick method.

John
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Old 10-04-2007, 11:17   #6
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Quote:
Originally Posted by senormechanico
Gord,

The resultant air pressure in the Tank Tender is proportional to depth of the liquid being measured, so if it's in a tank with vertical sides, it's a good measurement of gallons left, but if the tank has tapered sides, you can only know the depth, not the volume.

Steve B.
This is what I'm concerned about, as all of my tanks taper to the shape of the hull. I currently use the stick method for my fuel, and I can check my water tanks by removing the inspection plates, but that, frankly, is a pain. The waste tank is just a guessing game, and I've guessed wrong in the past! The tank tender seems like the perfect solution, especially since there isn't any electricity needed.
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Old 10-04-2007, 11:34   #7
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Of course, Steve B. Is right.

TANK CALIBRATION:

Boats and RV's are constructed of a wide variety of tank shapes and sizes. For simple shapes, the following methods of calibration seem to work:
1) Measure the width and length of the tank in 1" levels and calculate the number of cubic inches for each inch of height.
There are 231 cubic inches in a gallon. Therefore, the number of cubic inches divided by 231 will give you gallons per inch of the tank height.

2) A tank can also be calibrated by filling it with a metered flow hose or with a 2 or 5 gallon container and reading the Tank Tender each time 2 or 5 gallons are poured into the tank.
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Old 10-04-2007, 11:42   #8
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We have one on our boat and use it for the four tanks that we have . It works well. We also have a chart to tell how many inchs equil how many gallons.
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Old 10-04-2007, 11:46   #9
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The Water Computer control unit, from Offshore Systems, measures the water used, and the water added to the yachts freshwater tanks from a watermaker.

Goto: Water Computer
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Old 10-04-2007, 14:09   #10
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Thanks for the replys. For those who have installed the system, are there any issues with installation that I should know about? One question I have off the top of my head is how do you keep shavings from falling inside the tank when drilling holes for the tubing? (particularly the fuel tank). Also, does the tubing have to stay above the hole you have drilled for the tubing in the tank? I'm assuming it does, to prevent a siphoning effect, right?
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Old 10-04-2007, 15:22   #11
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I don't have one of these systems but I've drilled lots of holes in boats.
Just turn on a vacuum with the hose right next to where you're drilling and you'll get 99% of the bits.

The hose is full of air and as long as you don't get a siphon started before installation is complete, you shouldn't have a problem.

Steve B.
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Old 10-04-2007, 17:10   #12
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we have had Tanktenders on our fuel and water tanks for over 12 years. They were a breeze to install, have never failed and are a better indicator of actual fuel and water on board then any other guages we have come across. And yes you can calculate the amount in your tank based on the shape and get an accurate reading. But the easiest way is to start with an empty tank if you can and add fluid in measured amounts and note the readings.
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Old 10-04-2007, 19:35   #13
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Chuck, tell me more about Tank Tenders. I have two fuel tanks, both trapezoidal mounted athwartships, and six (!) separate water tanks, roughly triangular in shape mounted port and starboard of the salon bilge. Do I gather that I'd need a separate Tender for each tank? And must one have line-of-sight on the tank to monitor levels? I like to think I'm Capt. Anal, but realistically if checking levels will involve me pulling up most of my salon sole, I bet I'll often find something else that needs checking...

Gord, I like the idea of the Water Computer—brilliant, just measure usage! Might make boocoo sense for me with all my damn tanks. Is there any such device available for fuel tanks? I would think Offshore Systems would call it a "Water/Fuel" Computer if it worked for fuel too.
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Old 10-04-2007, 20:43   #14
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Geoff, The panel I have will monitor 3 tanks and I believe there are panels that monitor more. They have a small plastic tube that runs from a very small hole in the top of the tank to the panel. If you check their web site you can see all of the options with monitor for up to 8 tanks I believe. They also have install info as well as computing volume.


Look here for their Home Page
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Old 10-04-2007, 21:13   #15
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Quote:
Originally Posted by Geoff S.
Chuck, tell me more about Tank Tenders. I have two fuel tanks, both trapezoidal mounted athwartships, and six (!) separate water tanks, roughly triangular in shape mounted port and starboard of the salon bilge. Do I gather that I'd need a separate Tender for each tank? And must one have line-of-sight on the tank to monitor levels? I like to think I'm Capt. Anal, but realistically if checking levels will involve me pulling up most of my salon sole, I bet I'll often find something else that needs checking...

Gord, I like the idea of the Water Computer—brilliant, just measure usage! Might make boocoo sense for me with all my damn tanks. Is there any such device available for fuel tanks? I would think Offshore Systems would call it a "Water/Fuel" Computer if it worked for fuel too.

For fuel flow you need something like a Floscan meter as diesels generally have a return flow.
Floscan Instrument Co. Inc.

You buy one tank tender, it has a selection switch to select which tank you are going to read. On installation you run one tube to each tank. Each tube has to go to the bottom of each tank when you first install it. After that you just select the tank of interest, pump the pump handle and look at the gage. What you're doing is pumping air down the tube to the bottom of the tank. The pressure due to the liquid level is read on the gage.

As suggested above empty the tank, pour in x gallons at a time, use the tank tender to read a value, make a table of gallons versus meter reading.
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