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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 08-31-2010
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Virtual Fresh Water Tank

I originally posted this in the "How To" section, but noticed that this section gets a lot more traffic...So here goes.

I've been lurking around Sailnet for years, gathering and using knowledge, and benefiting from this community enormously. I figured I better throw a dime in the slot to do my part.

This post relates to the use of city water pressure aboard boats. We've all heard the stories of boats that sink at their slip because it was hooked up to city water and an internal hose gave way and the bilge pump didn't work because the power went out, etc, etc, etc,.... There have been heated threads dedicated to the problem of how to get fresh water from the spigot on the dock onto a boat. The two options are, hook 'er up to the city and throw caution to the wind OR fill 'er up every week or so with a dockside hose (i.e. run out in your bathrobe with shampoo in your hair and wave hi to the neighbors while you wait for the tank to fill). Neither is a great solution.

I was faced with this problem two years ago when after throwing caution to the wind and choosing option 1. Up to this point we were hooked to the city water with a hose and relied on a little shutoff valve on the water intake which we (my wife and I) were hit or miss on whether we actually used it or not. Sometimes we'd leave for a week and have forgotten to turn the valve off...This is how people get into trouble. Our number came up one day and I was fortunate enough to be on board when a water heater hose gave out and city water came flooding in.

We went to filling the tank every week, but that is a real PITA if you've been enjoying non stop water flow for the preceding year. So I looked for an alternative to the two game plans. Idea 1 was a button operated solenoid on a timer (press the button, get water for ten minutes) but this requires power to the button and the valve which would have to be onboard, no good. Idea 2, remote control something or another to the spigot which would open water flow when a "key" was aboard...again, full of holes, not to mention WAY too complex.

In my searches for various valves and such I came across a volumetric metering valve made by a company called Bermad. It's a tank filling valve that allows you to select the number of gallons you want on a dial... In the case of mine, between 5 and 125. I got to thinking and realized that my bilge could easily handle 75 gallons or so. What I had been trying to do is control the ingress of water at the time of use, what I realized with this valve is that it would control the ingress of water at the time of failure...75 gallons (or whatever you want to set it at) then ZIP it will shut off the water until the dial is reset. This valve requires no power and lives OUTSIDE on the deck of my boat, inline with the fresh water hose, doing its handy work before entering my boats water system. In essence, it's a virtual tank, but rather than filling it with a hose, you reset it with a dial... Much easier and quicker than hanging out on the dock in your bathrobe. We still use a shut off valve, and are better about turning it off when we leave the boat these days, but this is a great fail safe and it has worked flawlessly for two years. We've had 2 hose ruptures for various reasons and the valve saved the day both times. The part number is Bermad 1106-MTA-125, it costs about $100, plus you need fittings to make it compatible with your average hose. Here's to not sinking our boats. I hope this information is helpful to a few of you out there.
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Old 08-31-2010
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I don't think any city water hookup is desirable on a boat - whether you're relying on a hose clamp or a mechanical item there is a risk. Filling a tank once a week is not a real problem.
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I agree with mitiempo; connecting the dockside water up to a boat is inviting problems. Most dock water is at a pressure significantly higher than your boat's probably used to and with plastic hosing, splitting can be a real problem. I know of one boat that nearly sank when a fresh water line cracked and put 2" of water on top of the cabin sole.

There are two possible solutions: fill the tank and disconnect the hose, use the dock water only when you're on board and turn it off when you're not using it.
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I've been thinking about building a remote control valve (off the boat) that you would turn on when the tank runs low to refill it, and it would automatically turn off after a time or certain volume of water went through it. So you have the benefit of not having to leave the boat to fill the tank, but without the risks of the constant connection to shore water, nor the pressure of shore water. I'm thinking this would be advantageous in the winter.
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And another thing... how do you even attach pressure water to a boat anyways? If you were to screw a hose into the tank fill deck fitting (which I don't think would fit, but maybe it does), you still have the problem of the tank's air vent. Wouldn't you just be spilling water out the vent? And I don't think these vents are always to the outside of the hull, in which case you're filling up your boat even absent a failure in your plumbing...
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Old 08-31-2010
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Given that it is not desirable to allow ship's water to simply sit and potentially stagnate in ones tanks, it would seem wiser to refill the ships tanks when necessary rather than go through the brain damage of trying to concoct a fool proof shore-side water connection, no?
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"use the dock water only when you're on board and turn it off when you're not using it."

I agree, though the problem with this approach is that people forget to turn it off, best intentions aside, I am one of those people.

Being that my boat was a former racer, I'm not blessed with much tankage, making the "fill it when it's empty" approach fairly cumbersome. At 25 gallons, some weeks My wife and I would have to fill it 3 times. For us, adding another tank is not an option worth considering at this point.

The "virtual Tank" approach is simply the best for us when you weigh the various factors. Yes, there is some risk of potential failure involved, but I would argue that that risk is extremely low, perhaps even less than the risk involved with having to fill my F/W tank on the icy docks in the morning before I have my coffee.
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Our city water connection is an inlet with a female hose thread and a pressure regulator. It's plumbed into the system with a non return valve that keeps the pressure from filling the tank.

We haven't had a problem with city pressure where we live but I'm sure others might elsewhere, even with a regulator.
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Best reserved for trailers and motorhomes - they don't risk sinking.
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I don't think it's a bad idea. I'm not allowed to leave a hose connected to my boat at our yacht club, but if I were I might do this. I plumbed my boat with pex so no worries about over pressure, but I still wouldn't want to forget to turn the water off for a week without some sort of safeguard. For me the bermad valve would be a perfect solution.
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