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josrulz 10-17-2010 04:53 PM

Fresh water tank vent location options
Hi all,
I tried searching on this, and just couldn't find results amidst all the threads on holding tanks, vents, etc. If there's a link or something that I should read, please let me know.

On our 1984 Sabre 34, we have two fresh water tanks under each settee. Each has a vent line that runs forward, where they are T'd together under the V-berth, and then vented into the anchor locker.

I may need to move that anchor locker vent location due to some modifications in that area, and I'm wondering if I can choose a different location for the fresh water vent. Are there other options? Best practices for freshwater vent location and/or design? Other common locations on monohulls (if it differs on catamarans)?

I looked through most of the books I own, and the best I cold find was that there should be vents, and that's about it. Any thoughts on this?

remetau 10-17-2010 06:43 PM

Our tanks vent to our galley sink.

josrulz 10-17-2010 06:55 PM


Originally Posted by remetau (Post 655354)
Our tanks vent to our galley sink.

Thanks remetau, can you be a little more specific about the fixture? Sorry--I'm not familiar with that set-up, though I've heard reference to it.

Sabreman 10-17-2010 08:03 PM

Could you put in a T fitting to the sink drain?

Boat looks good, Jim.

josrulz 10-17-2010 08:16 PM

Thanks Sabreman.

Wouldn't T-ing it to the sink drain risk contamination of the tanks? Perhaps I'm not getting it.

mitiempo 10-17-2010 08:31 PM

1 Attachment(s)
Don't put the vent into the sink drain. It will contaminate the tank.

Some boats vent to the sink like shown below (older Swan). The other option is high in the boat near the tanks, ideally on center. When filling water will come out the manual water outlets at the sinks first as they are lower than the vent. Inside vents avoid salt water contamination.

remetau 10-18-2010 06:20 AM

Yes, my vent is much like the one in the picture above.

sailingdog 10-18-2010 11:26 AM

Venting the tank inside the boat makes a lot more sense than venting it externally. Putting a freshwater tank vent on the hull is just asking for contamination, especially if you dip the rails when sailing. :D Venting them to a fixture mounted above the galley sink makes sense so that any water that does come out drains out the sink.

Sabreman 10-18-2010 11:54 AM

All the descriptions make sense, but now I'm confused. Like josrulz, my vent is in the anchor well which definitely gets wet. While quite a bit higher than the tanks and faucets, I now wonder why I don't receive any contamination. Perhaps the vent is a one-way valve. That's the only explanation that makes sense to me.

mitiempo 10-18-2010 01:06 PM

It is designed to vent air, not water. I doubt it is a one way valve.

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