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Go Back   SailNet Community > On Board > Gear & Maintenance > Fresh water tank vent location options
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Topic Review (Newest First)
07-10-2014 05:37 PM
Philzy3985
Re: Fresh water tank vent location options

I guess for the sake of varying answers, I'll chime in.

On my Catalina 30, the fresh water tank(s) vent together up through a stanchion, and out a small hole drilled through the side of the stanchion into the stem. My guess is that the particular stanchion was designed for that, or there's a small vent on the deck, which the hollow stanchion was placed above.

Anyway, they probably did that over 6,000 times while making that boat and other Catalina's, so it must have a good reason.

Such a beamy boat, I've never been close to burying the stanchion that deep on a heel.

Also it's worth mentioning that I don't drink the tank water, just use it for cleaning my hands and dishes, occasionally to brush me teeth. Being almost 30 years old, I'm sure there's stuff in there, marinating, that I don't want in me.
07-10-2014 01:33 PM
Puddin'_Tain
Re: Fresh water tank vent location options

I realize that this isn't a solution for everyone, but here is how I handle water storage on my 27' boat.

I have a 20 gal tank under the aft end of the v-berth that is vented via a small diameter tube (which I should probably replace, as its pretty nasty-looking) to the anchor locker. Since the boat gets weekend use (at best), the tank and associated plumbing are basically just a big microbiology culturing experiment as far as I'm concerned (although, I do add a slash of Clorox whenever I fill the tank so the water is probably safe to drink, if somewhat unpalatable). So, I use the water in the tank for washing purposes only, and stock several 2.5 gal carboys of "Spring Water" from the grocery store as drinking and cooking water. We also usually carry a case or two of individually sized water bottles and plenty of other bottled drinks. Even on a week-long coastal cruise with two adults and two teenagers (yes, a 27' boat gets pretty crowded under such circumstances), such an arrangement seems to work just fine.
07-10-2014 11:21 AM
RichH
Re: Fresh water tank vent location options

Suggestion - put a run of small diameter (3/8-1/2" dia) tubing from the TOP of the tank into one of the 'highest' levels inside your cabin, terminating near the 'coachroof' (inside a hanging locker works best). Take a fist sized wad of 'freshly opened' bandage cotton fluff and place it (loosely) on the end of the open tube, cover this with 'bandage gauze' and 'tape' to hold in place and allow free flow of air. Keep it DRY and change out every 6-12 months. Cost: about $6 plus tubing.
.... then, Disconnect / block / remove the fungus/bacteria filled OEM 'vent'
07-10-2014 11:11 AM
Captainmeme
Re: Fresh water tank vent location options

Thanks RichH. Because of your explanation I won't be wasting effort, time and money installing a sediment filter on the fresh water vent line.
07-10-2014 10:48 AM
RichH
Re: Fresh water tank vent location options

Quote:
Originally Posted by Captainmeme View Post
Is there any reason one could not use say a 1 micron 10" standard sediment water filter instead of these "capsule filters"? The same kind of filter used in under the sink filters for water consumption? Yes one would have to add some adapters to the filter housing but the advantage is standard filter, reasonable cost and available at big box stores.
Some very good reasons for not relying on variable ÁM and non-hydrophobic filters in a vent line from a 'big box store'.

Such filters are not 'hydrophobic' ... a filter used in gaseous service (vents are 'gas' service) will seriously degrade in ÁM retention ability if it becomes 'wetted'. Hydrophobic membranes dont become wetted per se and therefore dont lose their ÁM retention because the filter media remains 'dry' or become totally 'blocked' (no gas flow) when wetted.
As an example, a hydrophillic (wettable) filter rated at ~0,5ÁM (gas rating) will be only able to retain ~5,0ÁM or greater when the filter media becomes wetted ... about a magnitude less in retention, meaning that all/many of those particles already captured will be released when the filter media gets 'wet'.

Big Box stores dont sell/offer hydrophobic filters; plus, the 'liquid' filters they do sell are very variable in the advertised ÁM 'rating'. These filters are NOMINALLY rated, meaning that their efficiency of capture at their 'rating' may be between only 50% to 90% of particles captured at that 'rating'. And, the housings used are either flat gasketed or 'knife edge seal' (filter-to-housing) which is incompatible for reliably retaining particles at much less than ~5ÁM .... such particles can usually easily 'bypass' through the flat gasket area. Once one needs to filter below 5ÁM (liquid) double O-rings in a 'piston seal' housing are needed to prevent such 'bypass'. For a vent you need very high efficiency of retention for both the filter AND the housing, as one or a few 'living' particles that bypass can easily morph into a large 'colony' if they 'get through'.

Summary .. the big box store stuff is very low technology and a lot of it is 'cheap junk'; but, is OK for crude RE-filtering of 'drinking water' .... or, for retaining waterborne pathogenic CYSTS (oocysts) but if and only if the oocyst filter cartridge has a listed 'retention validity claim': "99.99% retention of oocysts", etc.



Also FWIW .... that 16 mesh plumbers code is obsolete especially in areas that have a high potential of chlorine resistant oocyst contamination. It would remain applicable only for well water sources or in municipal systems (drawing from surface water) that have been 'updated' to coarse RO --> 1,2ÁM (99.99%) post treatment.
07-09-2014 02:03 PM
pdqaltair
Re: Fresh water tank vent location options

The plumbing code calls for 16 mesh filters on portable water storage tanks. The point is to keep out larger debris and bugs. I bet a few are crawling in there, specifically mosquitos. All you need to solve this is the cheapest Shurflo strainer.



The tank is never going to be sterile (impractical to filter that slow at the dock), so 16 mesh + a no-seawater location seems practical. Inboard vs. overboard? I think that depends on the specific geometry. Mine is over board, and since it is also an overflow, it works fine. But it is a boat-specific solution (the vent opens down, through the bridge deck).
07-06-2014 01:36 PM
mitiempo
Re: Fresh water tank vent location options

Vent inside. Sediment filter everything going into the tank. High quality filter before use at the galley taps.
07-06-2014 01:10 PM
Captainmeme
Re: Fresh water tank vent location options

"I never thought about a bio filter on that line. How is that different from air that gets into the system from other sources (e.g., while repairing stuff)? I always though it would be enough to add chlorine to the tank while filling after an initial shock treatment.
"
Good point about air getting into the system from other sources. Maybe, this is a WAG, with all the sloshing around from sailing to weather the chlorine evaporates leaving the water prone to infection. Not to crazy about venting over board. Might let sea water into the tanks.
07-06-2014 12:11 PM
SuperV
Re: Fresh water tank vent location options

I know that the original thread is from 2010, but since it was warmed up I came across it and don't think I saw in any of the replies a mention of a bend to allow venting overboard. Granted, venting inboard is best, but if I have a bend that brings the hose up as high as possible under the deck, I would think that should suffice. I never thought about a bio filter on that line. How is that different from air that gets into the system from other sources (e.g., while repairing stuff)? I always though it would be enough to add chlorine to the tank while filling after an initial shock treatment.
07-06-2014 07:48 AM
SkywalkerII
Re: Fresh water tank vent location options

My Tartan 27's fresh water tank vents inside the anchor locker, FWIW.

SKywalker
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