Water tank level

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Iggy

Guru
Joined
Mar 1, 2020
Messages
891
Location
United States
Vessel Make
Pacific Trawler 40
As some of you know I have a new to me Pacific Trawler 40, a 2001

I am trying to figure out how to monitor the water lever. The boat has two 100 gallon aluminum water tanks. It would be easy to meter the water going in but out would be a lot harder.

What have you guys done in trying to monitor the level?

The other side to this, for small trips I don't need to carry 200 gals for a 2 or 3 day trip.
 
I usually “stick” the depth. If you’re consistent the way water is used, over time you’ll know within 5% to 10% how much volume are in your tanks. Are your two tanks equalized by using cross-over plumbing? You might also check out the “Scad” system. We use Scad in our fiberglass holding tank. Works well. Scad makes a sending unit for metallic tanks as well. Good luck!
 
When I had AL rectangular cross section tanks, I spent decades just using a dowel calibrated in 10% increments. Nowadays, I have a plastic tank which cannot be "stuck" because of the silly angles in the fill hoes, but I can see the level by lifting the cockpit hatch if I begin to lose confidence in the factory installed WEMA level sensor and gauge combination.
 
Iggy said:
As some of you know I have a new to me Pacific Trawler 40, a 2001

I am trying to figure out how to monitor the water lever. The boat has two 100 gallon aluminum water tanks. It would be easy to meter the water going in but out would be a lot harder.

What have you guys done in trying to monitor the level?

The other side to this, for small trips I don't need to carry 200 gals for a 2 or 3 day trip.
Click to expand...

To get an approximation, assuming your tanks are at the stern of your boat, mark the top of your bottom paint at the waterline with full tanks and again with empty tanks. In between, just keep an eye on those marks. Soon you will know when to fill up.
 
My water tank and fuel tanks have sight glasses and the holding tank is plastic.
I also have a Maretron system for the fuel, water and holding tanks. This reads out at the helm station area.
 
OldDan1943 said:
My water tank and fuel tanks have sight glasses and the holding tank is plastic.
I also have a Maretron system for the fuel, water and holding tanks. This reads out at the helm station area.
Click to expand...
Me too!:blush:
 
I emptied by tanks through use and then filled them up with one of these attached to the hose/spigot:

Orbit Hose End Water Flow Meter Black https://www.amazon.com/dp/B0187BOFD...t_i_TYFQZ2EPBN3DAAA99BRN?_encoding=UTF8&psc=1

As I filled up, I noted the level read on my electronic gauge and gallons of flow measured by the device. I do similar occasionally to double check things. I can't vouch for its accuracy, but it has been precise. Also, it does have a reset feature, which I use after flushing the hose and before filling to avoid the need to do math.

I've had it for ~14 months, out in the Florida sun on the spigot the whole time, and it still works. So, I am pleased. I thought it'd be a one season toy, and, really, anything more than a day was a bonus w.r.t. the one time use I bought it for.
 
I can tell if mine are full, they overflow. After that, guesswork,although there is an old skill in Australia of rapping corrugated iron (plastic too) water tanks with your knuckles and determining by sound the level. At a more practical level, there are externally attached systems to read the level of black water tanks, would they work for "white water".
 
Giggitoni said:
I usually “stick” the depth. If you’re consistent the way water is used, over time you’ll know within 5% to 10% how much volume are in your tanks. Are your two tanks equalized by using cross-over plumbing? You might also check out the “Scad” system. We use Scad in our fiberglass holding tank. Works well. Scad makes a sending unit for metallic tanks as well. Good luck!
Click to expand...

Yes, the 2 tanks can be equalized.

I went to their web site. Scad is stating " SCAD internal sensor available for metal tanks;" I will e-mail them and see, but one problem is getting into the tanks. Thanks!

Dip sticks can not be used as there is no way to get into the tank itself.
 
Last edited:
koliver said:
To get an approximation, assuming your tanks are at the stern of your boat, mark the top of your bottom paint at the waterline with full tanks and again with empty tanks. In between, just keep an eye on those marks. Soon you will know when to fill up.
Click to expand...


Thanks! If nothing else, that will give me a rough idea.
 
gkesden said:
Orbit Hose End Water Flow Meter Black https://www.amazon.com/dp/B0187BOFD...t_i_TYFQZ2EPBN3DAAA99BRN?_encoding=UTF8&psc=1
Click to expand...


We use the same unit and it has worked well. I have ours installed on the outlet of a water filter system in the engine room so filled the tank and ran all the water out to check the capacity. Seems quite accurate and we haven't run out of water since. It reports both the most recent usage and total so it's been interesting and helpful to find out how much a shower or a dish washing use. Guess whose shower uses twice as much water:)
 
currently use a stick. Have just installed scad external stick on on holding tank but not yet sure it is working correctly ( no time to check and confirm)

For the water tank I am considering a sight tube vertically teed into feed line inside aft cabin closet for easy access. At the top a simple on/off tap to open to air to allow it to equalize to tank level.
 
Last edited:
koliver said:
To get an approximation, assuming your tanks are at the stern of your boat, mark the top of your bottom paint at the waterline with full tanks and again with empty tanks. In between, just keep an eye on those marks. Soon you will know when to fill up.
Click to expand...

Uh, well, no. 200 gallons of water weighs ~1400 lbs. The tanks are located approximately six feet aft of the center of buoyancy, which is close to midships on the Pacific Trawler 40. The "weight to submerge an inch" (a measure of the trim sensitivity of the boat) is several thousand pounds an inch. To measure a one-inch change in waterline submersion at the transom would require approximately 2000 pounds placed AT THE TRANSOM. Removing 200 gallons of water from a location about 14' forward will result in an immeasurable trim change.

All this info is from a former owner of a Pacific Trawler (me) who attempted to correct a bow-down trim state caused by the three foot transom extension added by Pacific Trawler to create the 40' version. I found the boat needs about 2000 lbs. of lead in the lazarette to trim properly, even with all water and fuel tanks full.

In my experience with my Pacific Trawler 40, those 200 gallons of house water was more than sufficient for my needs, even on extended trips throughout the PNW. I soon learned to re-water after a week or so underway, and never ran out. And never missed a water tank gauge. Your mileage may differ, of course, but one of the many virtues of the Pacific Trawler 40 is it's ample tankage.

Regards,

Pete
 
jungpeter said:
Uh, well, no. 200 gallons of water weighs ~1400 lbs. The tanks are located approximately six feet aft of the center of buoyancy, which is close to midships on the Pacific Trawler 40. The "weight to submerge an inch" (a measure of the trim sensitivity of the boat) is several thousand pounds an inch. To measure a one-inch change in waterline submersion at the transom would require approximately 2000 pounds placed AT THE TRANSOM. Removing 200 gallons of water from a location about 14' forward will result in an immeasurable trim change.

All this info is from a former owner of a Pacific Trawler (me) who attempted to correct a bow-down trim state caused by the three foot transom extension added by Pacific Trawler to create the 40' version. I found the boat needs about 2000 lbs. of lead in the lazarette to trim properly, even with all water and fuel tanks full.

In my experience with my Pacific Trawler 40, those 200 gallons of house water was more than sufficient for my needs, even on extended trips throughout the PNW. I soon learned to re-water after a week or so underway, and never ran out. And never missed a water tank gauge. Your mileage may differ, of course, but one of the many virtues of the Pacific Trawler 40 is it's ample tankage.

Regards,

Pete
Click to expand...
Thank you! Great to know.
 
Used a WEMA gauge on each of MOJO's tanks for 20+ years. Works great!
 
I have a 34 Californian with a 75 gal water tank. I installed a flow meter on the output of the tank. It measures the flow out of the tank. It is a P3 P0550 water meter from Home Depot.
 
For a simple, quick and inexpensive way to monitor water tank level, just fit a tee onto your equalizing line. Then run clear tubing up from the tee to a level above the tanks. Leave the top vented with filter or screen. Just mark it off in gallons or percentage full.
 
Another vote for the Tank Tender, mine will do five tanks, two fuel, two fresh water, and one black water
 
Fit a simple flow meter after your pump, top tanks, empty them, read metered volume and you know exactly how much water capacity have (but looks like yo already knows). Push the reset button when topping the tank and you are good to go and will find out how much you have left at any time. Simple, fool proof, cheap.

I am pretty sure you can even find a flow meter that you set to a predefined volume and it tells you how much is left.

L
 
I've just fitted a Gobius Pro to my holding tank. Sends an ultrasonic pulse into the tank at intervals that you can decide. I fitted mine at 3/4 full and for a water tank would fit at 3/4 empty. It blue-tooths to your phone, self adheres to the outside of the tank and they claim it will work on metal and plastic tanks.
 
AusCan said:
For a simple, quick and inexpensive way to monitor water tank level, just fit a tee onto your equalizing line. Then run clear tubing up from the tee to a level above the tanks. Leave the top vented with filter or screen. Just mark it off in gallons or percentage full.
Click to expand...

Bingo. :thumb:
 
Opaque plastic tanks
Easy enough to see level
No gadgets to fail.
 
The Hart system did not work well for us -- who knows why, as it is a very simple solution.


Maretron makes two different N2K solutions -- a sonar gauge that must be fitted to the top of the tank and a pressure gauge that goes at the bottom. We have both an Fintry and they both work very well. They have the advantage that you can set them to average over a user set period, so you get a good reading even in rough seas. We will probably end up using both on the new boat.


You could try using a plumber's snake or an electrician's wire puller like a dipstick down the fill pipe.


We've had gauges with floats in the tank, which work, but are not very accurate.


Sight gauges work well if getting to them is not too hard -- a piece of clear plastic hose tapped into the bottom of the tank with a valve at the bottom and leading well above the top.


As for how much you will need -- saltwater toilets or fresh? Showers? Swimming? On our circumnav, with saltwater heads, three people used a total of 15 gallons of freshwater daily. Mostly in the tropics, so daily short showers, but not much swimming.


And note above -- 200 gallons of fresh water is 1665 pounds, not 1400. A gallon of fresh water weighs 8.3 pounds.


Jim
 
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