Bi111ion
Well-Known Member
A water tank needs a vent to let air in so the water can get out. How can this be done so that the water does not come out if you have a knock down or an inversion? A non-return valve perhaps?
Water tank vent
- Thread starter Bi111ion
- Start date
Tranona
Well-Known Member
Normally the breather pipe goes in a loop well above the heeled waterline. This should cope with a knockdown, Inversions are vanishingly rare and if it did happen to you a drop of water coming out of a breather would be the least of your problems.
Bi111ion
Well-Known Member
Thanks, so I assume vent pipe is small enough bore not so much would come out then.
As for inversions being rare that is true, although I do sail with someone who survived an inversion in a yacht off Anglesea (unfortunately one of the crew did not). But I am working towards getting Tui prepared again for blue water passages, and that includes making sure you do not die in an inversion. Lockers and floor boards need some attention as well as stowage of gear. As well as not dying by being hit by floor boards it would nice to still have some fresh water to drink while you made a jury rig. I will eventually work out a good way to fasten down the cabin sole boards so that they stay put in an inversion but I can still pull them up in a panic wondering where I might have been holed. But as the tank needs a vent pipe now I thought I would try to do that right first time. Maybe you are right that a thin pipe looped up high and down again is OK without a check valve. But why not run that pipe down off the pipe going to the deck filler? Our deck is very high.
As for inversions being rare that is true, although I do sail with someone who survived an inversion in a yacht off Anglesea (unfortunately one of the crew did not). But I am working towards getting Tui prepared again for blue water passages, and that includes making sure you do not die in an inversion. Lockers and floor boards need some attention as well as stowage of gear. As well as not dying by being hit by floor boards it would nice to still have some fresh water to drink while you made a jury rig. I will eventually work out a good way to fasten down the cabin sole boards so that they stay put in an inversion but I can still pull them up in a panic wondering where I might have been holed. But as the tank needs a vent pipe now I thought I would try to do that right first time. Maybe you are right that a thin pipe looped up high and down again is OK without a check valve. But why not run that pipe down off the pipe going to the deck filler? Our deck is very high.
Carmel2
Well-Known Member
I think mine doubles up as the overflow, which drains over my anchor chain.
jwilson
Well-Known Member
I have sailed on a boat that got seawater into it's water tank via a breather at deck level, after driving hard with side decks awash for long periods. Used the emergency water that the race rules insisted we carry.
In practice the tank water would not have killed us, still mostly fresh but enough to make it taste slightly salty.
As others have said, the least of your problems if inverted. Have been there done that. Make sure the toolbox and stores of tins/jars etc cannot move as well as the obvious like floorboards. An interior awash with a mixture of seawater, scattered tools and broken jamjars is not ideal. There was also significant diesel in the mix. Don't remember any problems with water though.....
rogerthebodger
Well-Known Member
My 2 water tank vents doubles up as the overflow, which drains into my galley sink, so no chance of getting sea water into my fresh water tank.
rob2
Well-Known Member
The problem with a one-way valve is that the breather usually works both ways, letting air in as you use water and letting the air out when you refill. You could put a hand valve in to close it off when sailing and if you have a pressurised water system, the valve could be electrically operated by the tap or the pump.
Rob.
Rob.
jwilson
Well-Known Member
But might you get dirty dishwater in your tank?
Plum
Well-Known Member
My vent is inside the cabin and runs to the coach-roof deck head. Higher than the filler so it never becoms an overflow. Have never had a full knockdown but if i did hopefully seawater would never get into the tank......... unless.......
Www.solocoastalsailing.co.uk
RupertW
Well-Known Member
I'm now trying to think of some kind of gravity based stopcock - so if the boat goes upside down (or even on it's side) the pipe is blocked until the boat goes upright again. Heath Robinson is calling.
rogerthebodger
Well-Known Member
Not a chance.
This is my galley sink arrangement behind SWMBO
The mixer taps on the left is for the hot and cold pressure water. The small single tap on the right is the pressure sea water tap, fed from my deck wash pump.
Between the pressure taps are 5 spouts, 1 is fresh water from foot pump, 1 is sea water from another foot pump, 2 are fresh water tank vents/overflow and the 5th is an outlet from my water maker so the quality of the water maker output can be checked before the water maker output is diverted to either of the fresh water tanks.
As the spout outlets are all above the top of the sink no water can flow from the sink into and back down any of the spouts.
rob2
Well-Known Member
That is exactly what they used to put on cheap snorkels - an inverted cage with a ping pong ball in it!
Rob.
prv
Well-Known Member
How about just mounting a sounding valve upside down?
You get those on ship tank vents too, except that the ball is about 4" in diameter
Pete
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If you expect to spend that much time upside down that your water might run out, switch to flexi-tanks and then there's no vent.
Carmel2
Well-Known Member
Use the over flow to your advantage, mine exits over the anchor chain, so the chain gets a fresh water wash once in a while.
RupertW
Well-Known Member
How about just mounting a sounding valve upside down?
You get those on ship tank vents too, except that the ball is about 4" in diameter
Pete
Great - a new thing I have never heard of but now need 3 of them
prv
Well-Known Member
All the ones I've seen are three or four inches in diameter - not really yacht sizes
Pete
