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jr_spyder · 22-08-2014, 12:56

I had a funny discovery yesterday that I thought I'd share. I have three fresh water tanks on my boat: 90 gal in the bow under the v-berth, 40 gal low down amidships and 35 gal to starboard. There's a very nice manifold under the cabin sole where all tanks' supply lines meet, each with a ball valve, and the line to the pump is fed. I've never completely trusted the electronic gauges, especially the one on the mid tank, and have just had an instinct something wasn't right.

Last week my wife and I left the dock for a four day cruise with just the 90 gal tank full and the other two near empty. When we returned the gauges said we used all 90 gal in big tank - which didn't seem at all plausible as we're pretty miserly with water even on short cruises. Meanwhile the wacky gauge on the mid tank was showing about 75% full. These two facts were never so clear before. I opened the inspection port on the mid tank and sure enough it had miraculously refilled itself!

To make a long story short (a fair amount of troubleshooting and bloody knuckles) the ball valve at the manifold for the mid tank had started to fail and was leaking ever so slowly when closed. Since the bow tank was full and is higher up, and the lower mid tank was empty, there was a suitable siphon effect for the bow tank to put pressure on the manifold and all the closed valves, and thus backfeed water into the mid tank. So, darn it, I don't have a miraculous never ending supply of fresh water, but I have solved a mystery that's been lurking for a while. I think my gauges might actually be fine. I've changed the valve so now time will tell.

There's always something...

JR

Blue Stocking · 22-08-2014, 13:04

AW shucks !! I was gonna ask you to raft up and fill mine from that magic well,.

Matt sachs · 22-08-2014, 13:15

You carry 165 gallons.....nice!

Greg4cocokai · 22-08-2014, 13:24

Quote:

Originally Posted by Matt sachs

You carry 165 gallons.....nice!

We have 400 gallons!

jr_spyder · 22-08-2014, 13:24

Plus 12 more in the hot water heater. We also have a water maker that I've never turned on since I bought the boat ~3 years ago. Heading for blue water next year where all this will start to pay off. For coastal cruising it's kinda overkill. But that's how Ted Hood built his boats.

Matt sachs · 22-08-2014, 13:32

Im jealous. I thought my 85gallons and a watermaker was overkill

socaldmax · 22-08-2014, 15:40

How did 90 gal from one tank fit into a 40 gal tank?

Is the gauge that inaccurate, or did it overfill and vent into the bilge?

Reefmagnet · 22-08-2014, 16:21

Quote:

Originally Posted by socaldmax

How did 90 gal from one tank fit into a 40 gal tank?

Is the gauge that inaccurate, or did it overfill and vent into the bilge?

They probably consumed it.

We had the opposite thing happen to us early in the year. We have two identical tanks each holding about 40 gals. Headed out from the marina on a trip that was at least a week away from resupply. The weather was terrible and we motor sailed for about half an hour before we turned to run with the wind. The wife went down stairs to turn the engine off and found the bilge full of water (heard the bilge pump running). The source of the leak was our pressurised water system combined with a faulty hose clamp that let go on a newly replaced filter. "Thank goodness we have the other tank turned off" we agreed. Twelve hours later we reached our anchorage for the night only to discover that the "spare tank" was just about empty as well! Investigation revealed that the tanks are joined by a common fill tube. The "in use" tank was on the lee side of the boat while were heavily heeled and being hammered by the chop. This allowed the water in the reserve tank to transfer to the in use tank via the fill tube. Needless to say, we now make it a point to turn the both the fill tube valves off and the pressure pump when travelling!

jr_spyder · 22-08-2014, 17:33

Quote:

Originally Posted by socaldmax

How did 90 gal from one tank fit into a 40 gal tank?

Is the gauge that inaccurate, or did it overfill and vent into the bilge?

I don't think we left the dock with a full 90 gal. I didn't want to overfill/pressurize the tank so I stopped filling when the gauge said full , not when I got back pressure. Then we consumed some, and there was some still left in the 90 gal tank. So it works out.

jr_spyder · 22-08-2014, 17:41

Reefmagnet,

We had a similar situation very near after we bought the boat. The bilge pump was running non stop so we thought we were taking on water. It turned out that a loose hose fitting came apart and was draining our fresh water into the bilge with the water pump running.

We have a buzzer/light that goes off in the cockpit that tells us if a bilge pump is running. So that irritation got our attention and we found the problem quickly. We also have a buzzer/light that tells us if the fresh water pump is running but it wasn't working at that time. It is now. It's really nice to know when you're in the cockpit and can't hear stuff below if pumps are moving water around in your boat unexpectedly. Kinda of fun to tell guests I'll know if they're using too much fresh water as well!

JR

**StuM** · 22-08-2014, 18:00

Talk of leaking ball valves and fill pipes does point out one other thing:

Unless your multiple water tanks are plumbed completely separately, there is a risk of cross-contamination in the event of a tank being fouled. So always carry a completely separate supply of drinking water on passage.