Water tank vent... Stopping sea water getting in

[Danbury]

Does anyone else have the problem of sea water leaking into the vent ? Mine is deck mounted alongside the filler... and when there's green water flooding over the deck, the inevitable happens...

Is there a vent type that actually lets lets air in, but not water ?

 

[thalassa]

It is not entirely clear to me why you would want a freshwater tank vent on deck. In my old and present boat, it was/is simply high up inside, in a locker.

 

[HunterWanderer]

Mine is mounted in the hull side and there is a vertical loop of about 200mm and havent had a problem but it could happen.

Flexi bag tanks are probably better.

 

[prv]

Ariam's breathers are on the hull side, with a sort of aft-facing scoop to help prevent water going in when heeled over and travelling forwards. They also loop upwards to some extent. I'm not entirely happy with the arrangement, but touch wood it seems to work so far.

Kindred Spirit's breather was better - it was mounted on the centreline, on the aft face of the cockpit coaming, sheltered by the mizzen mast. The boat would need to be nigh-on submerged before that took on water.

I've been on boats that had a small chrome overflow pipe into the sink. This seems quite a good option if you don't mind the slight additional clutter in the galley.

Thalassa's option, simply high up inside the hull, could work well, though I think I would plumb it to the bilge (via a tundish or siphon break) rather than just have it spraying out into the locker if the tank were over-filled. I wouldn't choose it on a modern hull-form with a shallow bilge, where any water becomes a nuisance as you heel.

Pete

 

[prv]

It is not entirely clear to me why you would want a freshwater tank vent on deck. In my old and present boat, it was/is simply high up inside, in a locker.

Presumably because the assumption is that you will fill using a hose, and continue until you see water pouring out of the breather.

Pete

 

[coopec]

I agree with what prv says in regard to "you will fill using a hose, and continue until you see water pouring out of the breather"
Maybe an in-line non return valve installed just below deck level might be the answer?

Mmmmmm. maybe that's not so brilliant as the tank would tend to collapse as you pumped the water out

 

[coopec]

What you need is a sort of a dorade box over the vent but transparent so you could note the water flow.

I'm have been reading and thinking about this problem too. Some people have the outlet over the hand basin in the shower but unless you could see the outlet from the filling point you would need a second person to monitor the flow.

 

[coopec]

Maybe one of these?

http://www.discountmarinesupplies.com/FUEL_SYSTEM_Fuel_Tank_Vents.html

 

[lw395]

You can put a one-way valve on the permanent vent, so it only lets air in.
You can then open a vent or second filler on deck to let the air out while filling.

My last boat had twin tanks, with the breathers connected together over the heads sink.
You could put a one-way on that breather and fill with both tank fillers open.

Maybe not ideal if cruising in dodgy areas where you want to keep one tank separate in case of dodgy water.

You could probably just let the air belch out of the filler, it's not like getting diesel on deck, and water usually runs slow enough, but it's not always good to be seen wasting drinking water, and sometimes it will hit you in the face, not great in winter.

 

[Danbury]

Maybe one of these?

http://www.discountmarinesupplies.com/FUEL_SYSTEM_Fuel_Tank_Vents.html

That's what I have right now... and that can let in green water...

 

[Danbury]

Thanks for all replies...

I think on balance, an internal vent is best, but one that vents over a sink/shower...

 

[Stork_III]

Thanks for all replies...

I think on balance, an internal vent is best, but one that vents over a sink/shower...

Mine is led to high in the anchor locker, well protected in green water sailing.

 

[rob2]

I think the whole subject of tank vents was nicely addressed in the PBO Sketchbooks. The option I particularly like is to take the vent hose up inside any vertical SS tube - e.g. pushpit leg, gantry or wind generator pole. The vent is now way above the tank and protected from rain, waves, dust, idiots...

Rob.

 

[coopec]

Someone else has had this problem!
Fuel Breather Marine / Boat Fuel Tank Breather With Water Trap suit White Hulls

http://www.ebay.com.au/itm/Fuel-Bre...ith-Water-Trap-suit-White-Hulls-/261219463343

 

[john_morris_uk]

We are in the slightly odd position of having two vents. (Two separate tanks which we can close or connect together or not, but which must be connected together to fill both.) The starboard tank (that fills first) has a vent in the topsides just beneath the rubbing strake, whilst the port tank has a vent high up above the sink in the f'wd heads compartment. Best or worse of both worlds?

We have high topsides, but even in the roughest weather I've never detected any salt water polluting either water tank.

 

[MYStargazer]

I think the whole subject of tank vents was nicely addressed in the PBO Sketchbooks. The option I particularly like is to take the vent hose up inside any vertical SS tube - e.g. pushpit leg, gantry or wind generator pole. The vent is now way above the tank and protected from rain, waves, dust, idiots...

Rob.

Genius!!! I'm have the same issue, and this may just be a solution.

Will need to drill a small hole at the highest point of the pullpit railing though to let air in (my water tank's at the bow)...

 

[jwilson]

I think the whole subject of tank vents was nicely addressed in the PBO Sketchbooks. The option I particularly like is to take the vent hose up inside any vertical SS tube - e.g. pushpit leg, gantry or wind generator pole. The vent is now way above the tank and protected from rain, waves, dust, idiots...

Rob.

Did an ocean race in a boat with the vent tube up inside a midships stanchion tube to just below the lower guardwire. After some hard sailing found the tank water was getting salty. On the whole though an on-deck but very high up location seems best. On most modern high-freeboard boats the forward tank vent is inside the top of the anchor locker, and the aft tank vent is just up near the top of the transom, that will need the boat near-submerged to admit salt.

 

[lw395]

Did an ocean race in a boat with the vent tube up inside a midships stanchion tube to just below the lower guardwire. After some hard sailing found the tank water was getting salty. On the whole though an on-deck but very high up location seems best. On most modern high-freeboard boats the forward tank vent is inside the top of the anchor locker, and the aft tank vent is just up near the top of the transom, that will need the boat near-submerged to admit salt.

I've been on a 40ft yacht with the whole foredeck well buried in a wave, but I don't think we carried any water in the tanks for racing.

Depending on the seriousness of the passages to be done, I might want to know that the water will stay in the tank, and the sea out, through at least a masthead in the water event.
Another point is that convoluted plumbing can be a haven for mould and gringe that is hard to clean effectively.
I'm fussy about the water I drink, to the point where I often take bottled stuff.

 

[Hadenough]

Presumably because the assumption is that you will fill using a hose, and continue until you see water pouring out of the breather.

Pete

I'm wary now about filling until water comes out of the breather. We have a heavy duty rigid plastic tank, it's very rigid but there is some flex to the top. The 35mm filler spigot is right next to the 18mm breather outlet. I've found that if you fill too fast a huge bubble can form in the top of the tank which cannot get out of the breather. Only realised when the cabin sole popped off the screws recently. Moral is fill slowly as I think Uncle Tom C advised in a mag article some time ago.

 

[rob2]

Just remembered that on one boat with a deck level breather, part of the new crew's induction was to be shown the breather and told "Gentlemen, this is a no pissing area".

Rob.