Dual water tanks - draw from both or one at a time?

[SoSound]

For those who have two fresh water tanks; do you pump from both tanks at once? Or, do you use most from one tank and then switch over when necessary?

My system has a manifold which can open one tank at a time, or both at once. I have been drawing form just one tank at a time, and it eventually makes a little bit of a difference in the fore-aft balance as I drain one tank at a time. Nothing that I can actually feel or measure, it just looks odd when one tank is empty and the other one is full.

 

[quadrille38]

Previous boat had two tanks and I always drew off one at a time and alternated. That way I was sure I wouldn’t run out. Current boat only has one tank of 75 gallons. I wish they’d have split that into two when they built the boat.

 

[kloudie1]

One at a time..

 

[kappykaplan]

 

[jssailem]

Dave. I have two 50 gallon tanks, one port, other starboard. They are above and outboard of my two 80 or so gallon fuel tanks. I alternate the use of the tanks drawing on the starboard fuel and the port water. If an imbalance starts to appear then I check levels and will switch if a tank is nearing empty. I try to maintain near zero degree heel.

 

[dlochner]

When we are out on a extended trip, we draw from one tank at a time. First the bow tank to lighten the bow, and then the starboard tank. When one is empty, it is time to think about finding water in a couple of days. Also it is easier to check the level of the starboard tank than the bow tank.

When we're not out cruising we just use one tank, the starboard tank that is under the salon sette.

And right now there's a leak some where and I ain't a happy skipper.

 

[Davidasailor26]

Another vote for one at a time. If one tank is empty the pump will pull air from there instead of water from the other. Admittedly I don't know if it's actually possible for there to be air in one tank and water in the other if the manifold is fully open, but I figure I'd rather not find out in the middle of a shower.

 

[Don S/V ILLusion]

If you have a water level gauge, it’s a non-issue. If you can’t know how much water if remaining (in both tanks), why invite an unwelcome surprise?

 

[dlochner]

Admittedly I don't know if it's actually possible for there to be air in one tank and water in the other if the manifold is fully open, but I figure I'd rather not find out in the middle of a shower.

It will depend on the location of the manifold. If one tank is completely above the manifold, it can be empty. If boat tanks are above the manifold then it will be impossible. Water will always seek its own level, so if the tank outlets are not on the same level, the higher tank will drain first until the water level is at the top of the lower tank and then they will drain evenly.

 

[JamesG161]

My 60 gallon tank is Center Balanced. The larger 100 gallon [ starboard slight offset] offsets the Galley cupboard. Plus now we stow all extra beverages on the starboard side. I did note a slight port side list until I move the stowed beverages.

Alternate them for sanitation alone.
Jim...

PS: Hunter did a great balancing design.
PSS: If I opened both, the 60 Gallon would fill the 100 from elevation differences.

 

[SoSound]

Thanks, everyone! I have two 34 gal. tanks. One is under the v-berth and one below the berth in the aft cabin (along side a 34 gal. fuel tank). The manifold is above the outlet for both tanks, and has a valve to control which tank (or both) to draw from. I think it sounds like a good idea to work from the forward tank, all else being equal... and, if not equal, then match the levels of the fuel and rear fresh water to balance things laterally.

 

[Stu Jackson]

Previous boat had two tanks and I always drew off one at a time and alternated. That way I was sure I wouldn’t run out. Current boat only has one tank of 75 gallons. I wish they’d have split that into two when they built the boat.

Right answer!

I find it incredible that anyone could tell trim differences from an empty water tank, but more power to anyone who can. Kinda like a crew member moving around.

 

[ToddS]

Two tanks... 100 gallons total... I do one, then close it and open the other. This is mostly because I don't have gauges (on my list of improvements to add, but haven't gotten there yet), and I can better estimate when I need to refill after one has emptied. My tanks are one in the bow, and one near the stern, and I absolutely can see the difference (in my 32 foot waterline) in how that 800 pounds (350+ Kg) of water is distributed. my boat already sits just a tiny bit lower in the stern than the bow with full water and diesel tanks, but if I empty the bow first, the stern sits way lower. I've never measured, but I'd estimate there is a difference of a couple full inches between emptying bow first, vs stern first.

 

[jviss]

Right answer!

I find it incredible that anyone could tell trim differences from an empty water tank, but more power to anyone who can. Kinda like a crew member moving around.

Yea, a 300lb. crew member.

 

[jssailem]

if I empty the bow first, the stern sits way lower.

From an engineering point of view, a good reason to put your water tanks low, parallel the center line and amidships. I use the heel meter to judge if I should start drawing from the other tank. Pretty easy to keep the boat sailing upright.

 

[Tally Ho]

I have 2 30-gallon tanks, under settees on port and starboard sides, mid ships.

I have a manifold that allows me to draw one tank at a time.

As others have said, I don’t have tank gauges, so I run one tank until empty, and then switch.
That way I don’t run out completely.

I also think it helps to keep the water fresher (but maybe just my perception).

Greg

 

[sail sfbay]

My sailboat has 5 tanks ( 1 forward, 2 mid-ship starboard and 2 mid-ship port) with tank level monitor. I pull water off all the tanks simultaneously that way I mitigate the risk if bacteria growth in idle tanks.

 

[jviss]

My sailboat has 5 tanks ( 1 forward, 2 mid-ship starboard and 2 mid-ship port) with tank level monitor. I pull water off all the tanks simultaneously that way I mitigate the risk if bacteria growth in idle tanks.

Yes, but if one suffers a leak, you stand to lose all your water, depending on how they are connected.

 

[sail sfbay]

"Yes, but if one suffers a leak, you stand to lose all your water, depending on how they are connected."

For long passages I totally agree. Should have clarified that is an acceptable risk for bay, delta and coastal cruising. All 5 tanks are manifolded together to the water pump with a manifold station upstream of the pump.

 

[dlochner]

My sailboat has 5 tanks ( 1 forward, 2 mid-ship starboard and 2 mid-ship port) with tank level monitor. I pull water off all the tanks simultaneously that way I mitigate the risk if bacteria growth in idle tanks.

If you have shocked your tanks at the beginning of the season and if you use municipal water, there shouldn't be much of a problem with critters growing in the tank.