Any advice? Tank Tender Reading?

[SteveNewport]

Hey guys. Our 1991 Hatteras 41c has a Tank Tender to measure the level of Fuel, Water and Waste.I just filled the fuel tank completely to the top (500 gallons). When I dipstick the tank, at completely full, it is between 28” and 29” on the stick.When I tried the Tank Tender, it shows about 26.5” (and someone has written a little arrow on the gauge as well).Questions:1. I assume the Tank Tender “inches” are supposed to correspond to the actual inches of fuel in the tank? So I should be seeing “28.5” on the TT? Is that correct?2. If that is correct, any ideas why my TT is only showing 26”? 3. How do others use their Tank Tenders? Any advice?Thank you!!Steve

 

[SKYCHENEY]

The tank tender measures the amount of liquid in the drop tube that was installed for that system. If it does not extend all the way to the bottom of the tank, then your reading will be less. I suspect that is what is happening here. The only way to know would be to pull out that little plastic drop tube and measure it.

 

[Guy Walters]

Steve, inches of water is a pressure measurement on the Tank Tender gage not a measurement of depth. There are easy conversion charts for "inches of water" to PSI but that want help you either. The Tank Tender does not know the dimensions of your specific tank and therefore you have to build your own conversion chart. I just installed one for my water tank and holding tanks. They are simple to use and basically just require running an 1/8" plastic hose to the location, drilling and tapping a hole in the top of the tank, inserting another 1/8" much stiffer plastic hose to 1" off the bottom. The way I made my conversion table was as follows:
1. Empty your water tank
2. Take your water hose and time how long it takes to fill up two 5 gallon Lowes plastic buckets.
you can do any increment of gallons but I found 10 gallons was close enough.
3. Start filling, pull the hose out of the deck filler at the same allotted time and then check the Tank Tender "inches of water"
4. Write this down on you chart ie. 10 gallons = 1.2". (I just made that up but you get the idea)
5. continue to to do this until the tank is full.
It is easier if you have a helper and I found that it is better not to turn the hose off during measurements because the flow rate might not be consistent. I realize this is sort of a PITA but you only have to do it once. I laminated my chart and keep it next to the Tank Tender.
I hope this helps.
Guy

 

[Captain Ralph]

Guy has a great plan there.
He must have spent some time in my local swamps.

Dead weight of fuel is lighter than water so the pressure meter will read differently from the fuel tanks.
Luckily, Fuel pumps are a lil easier to figure gallons per tank level.
When we worked on our Bertram and tried to figure our oddly shaped fuel tanks to the gallons inside;
We scheduled with the fuel supplier their slowest time. Pumped, read the pump, took a picture of the fuel gauge, made notes.
Tipped the dock kid well.
Yep, our fuel tanks are no way linear when that gauge starts going down.

 

[SteveNewport]

The tank tender measures the amount of liquid in the drop tube that was installed for that system. If it does not extend all the way to the bottom of the tank, then your reading will be less. I suspect that is what is happening here. The only way to know would be to pull out that little plastic drop tube and measure it.

Thank you!

 

[SteveNewport]

Guy has a great plan there. He must have spent some time in my local swamps.Dead weight of fuel is lighter than water so the pressure meter will read differently from the fuel tanks.Luckily, Fuel pumps are a lil easier to figure gallons per tank level.When we worked on our Bertram and tried to figure our oddly shaped fuel tanks to the gallons inside;We scheduled with the fuel supplier their slowest time. Pumped, read the pump, took a picture of the fuel gauge, made notes. Tipped the dock kid well.Yep, our fuel tanks are no way linear when that gauge starts going down.

Yes, this is the same thing we did. Took a while, but now we know closely how much fuel we have at every inch demarcation in the tank. Thank you!