Best way to vent water tank

[Kapow13]

I have a port and a starboard water tank, located opposite each other amidships.
Each stainless tank has a separate deck fill. The port tank and starboard tank are connected via a low lying hose that traps water as it travels through the bilge.
I need to find a method to vent the port tank, which is isolated across the bilge from any sinks, preventing an inclined vent hose to sink overflow, as per the install on the starboard tank.

What is the best method to vent this port tank that avoids significant saltwater ingress or loss of fresh water supply during knockdowns?

[jordanbigel]

Our fresh water tanks vent into the shower compartment.

[ItDepends]

There is NO good reason that potable water tanks should EVER vent overboard, unless you count "easy and cheap to build" as a "good" reason.

Venting into a shower compartment is a good solution. If you have a brain fart and overfill the tank it overflows to a relatively safe, easy to clean up, place.

Installing a vent overboard for a potable water tank that is EVER susceptible to saltwater ingress is just showing that the builder does not understand what an ocean going boat is all about.

Worrying about what happens during a "knockdown" is be a bit extreme (I have been crossing oceans for decades, and never been "knocked-down") but salt water ingress to your drinking water can happen in conditions a lot milder than that if the vent is outside the hull.

[Kapow13]

Top of the port tank and offtakes are around 1-1/2' above the cabin sole - shower sump and sinks are located on the starboard side.

[Searles]

For years we have where possible put breathers for f/w tanks up inside stanchens ,a stainless pipe to just under the tube fitted for the lower life line in most vsls,gifting the Stan neon out and drilling down the centre of the base ,a small breather hole in the side of the base is needed ,neat and tidy .⚓️⛵️

[Stu Jackson]

Originally Posted by Searles

For years we have where possible put breathers for f/w tanks up inside stanchens ,a stainless pipe to just under the tube fitted for the lower life line in most vsls,gifting the Stan neon out and drilling down the centre of the base ,a small breather hole in the side of the base is needed ,neat and tidy .⚓️⛵️

Catalina has been doing this for years. I had a 1981 C25 and our 1986 C34 has two.
The side breather hole faces aft.
I have been the Secretary of the C34 Association for almost 25 years. There simply have been NO reports any contamination.
A few, very few have crossed oceans SF to Hawaii, LA to NZ).

[wrwakefield]

Our two potable water tanks vent into the galley sink. The seperate vent hoses Tee into a single hose that connects to a discharge line that empties into the sink.

Benefits include reduced risk of pulling contaminates [e.g., insects; salt water; etc.] into the tanks, and it is easy to tell when a tank is full... [e.g., like when filling from a hose or when running the watermaker...]

I can't think of any downsides in our case.

FWIW

Cheers! Bill

[Shrew]

Originally Posted by ItDepends

There is NO good reason that potable water tanks should EVER vent overboard, unless you count "easy and cheap to build" as a "good" reason.

Venting into a shower compartment is a good solution. If you have a brain fart and overfill the tank it overflows to a relatively safe, easy to clean up, place.

Installing a vent overboard for a potable water tank that is EVER susceptible to saltwater ingress is just showing that the builder does not understand what an ocean going boat is all about.

Worrying about what happens during a "knockdown" is be a bit extreme (I have been crossing oceans for decades, and never been "knocked-down") but salt water ingress to your drinking water can happen in conditions a lot milder than that if the vent is outside the hull.

I put loops that go above the throughhull. Similar to a fuel tank. You'd never vent a fuel tank inboard, yet with proper design thousands upon thousands of boat ply the ocean and don't contaminate their fuel or freshwater with seawater.

[Pelagic]

There is no "best" way just one suitable for your boat.

Perhaps for your Port vent ...a line Aft to the more protected cockpit via tiny covered vent

On my boat my vents for both diesel and water run inside the engine compartment vents up over the side scoop on the outboard house and curves down so they will overflow on the side deck....