water tank question

[Ken Heyman]

Last season I was convinced that I had a leak in my aft water tank. Recently after a thorough inspection using "complex" deductive reasoning (I looked at at my manual diagram), I realized that the aft tank could discharge its contents into the starboard tank if both valves are left open. What I don't know is whether this is normal or an issue that should be corrected. Presumably if both tanks are full and both valves open, the draw will be form the starboard tank?. I guess the answer may be to only keep one valve open at a time. Thanks in advance for the assistance.

Ken

[Sailing Steve]

Not a direct answer to your question, but I only open one tank at a time, beginning with the aft tank.  This gives me some "notice" on how much water I've used.  It also "moves" the balance of the boat forward as the water gets used.

Steve

'90 L'Abri
Hull# 1080

[Stu Jackson]

Ken

There are two schools of thought on this issue.

One, keep the valves open all the time, so the aft tank "drains" into the starboard (lower) tank by gravity.  Helps with "trim," as Steve mentioned.

The other is to only have one valve open at a time, which determines the tank that is being used.

I prefer th second, because I always know when a tank is empty and needs to be refilled.  When one goes, I refill it, but switch to the other tank, thus helping just a little bit in keeping the water "moving," and turning it over.  We haven't ever run out of water when away from a source, whereas if the aft tank is always draining into the forward tank, once the water goes, you're SOL.  Some have also discussed "cross contamination," but I haven't heard any real life stories about this happening.  Older tech notes discussed this subject a few times way back in the early days.

[Ron Hill]

Ken : On the 1987 and later MKI's the aft tank is higher than the starboard tank.  If you let both valves open, the aft tank will completely drain until it's empty and then you'll finally draw water from the starboard tank.

What I do is shut off the aft tank and draw water out of the starboard tank so it doesn't get "stale".  I do this for a day or 2 and thru a shower use or 2.  Then I open the valve from the aft tank and refill the starboard tank from the aft tank and shut that tank off again.  That way I use water from the starboard tank and keep the water circulating.  It's also easier to refill the aft tank which I refill with FILTERED water.  In a place like the Bahamas where water costs more than diesel !!,  I run the starboard tank dry, then fill from the aft tank and I exactly know the water consumption and remaining capacity. 
A few thoughts.