mystery vent question

[Craig Cook]

I was running the instrument wire from the chart plotter to the VHF this past weekend and was threading it past the holding tank which is located port side. I was generally checking things out in the locker/compartment where the batteries and holding tank are located and found that we have two vents, about a foot apart, installed in the hull port side just above the rub rail. One is plumbed to the holding tank the other is not plumbed to anything? I checked the schematics that came with the boat and there is no mention of a second vent port side. The fuel tank vent is starboard side aft, fresh water tank vent is starboard side forward, there is supposed to be a propane vent starboard side midships but there is not. Anyone have any thoughts on what this mystery vent might be for?

 

[Capt jgw]

Propane locker should have two vents, one high one low, the low one being the more important.
Whatever it was originally for, make sure it's plugged. If you were sailing rail down it would ship water, and let bugs in any time.

 

[centerline]

Propane locker should have two vents, one high one low, the low one being the more important.
Whatever it was originally for, make sure it's plugged. If you were sailing rail down it would ship water, and let bugs in any time.

in a propane locker there is no need to have two propane vents, and in most applications it would even be dangerous.... a lower one is required, and the lid at the top is required to be sealed so no vapors can escape to the inside of the boat or cockpit....... an upper vent would still have to be vented to the water side of the hull...

the fresh water vent should NOT go to the outside of the boat, as any spray or waves could contaminate the tank. it should be vented high INSIDE the boat.

the mystery vent could have been for a battery box, but which would have been too small of a vent for that purpose anyway, or it could have been for a second holding tank vent project that was never completed.... or maybe it was placed in the wrong spot to begin with, and another one had to be added in the "right" spot.... what a PO does to the boat before we buy them can be very puzzling sometimes

 

[Craig Cook]

Thanks for the input and I agree about PO's, but in this case it isn't a factor. I know the PO and he did NOTHING to this boat. If it needed to be done he paid a mechanic, but he was not a DIY guy in any way shape or form. I'm thinking your idea that the vent was placed in the wrong spot by the factory to begin with is spot on. I could see the assembler going back to the part guy and asking for a 6" longer piece of hose, being told no that all the hose is pre-cut to a certain length so here is another vent instead.

Regarding the propane locker, there is none. Very puzzling. The manual says there is suppose to be "something", they don't say exactly what, under the stove that is vented to the outside. The stove is a two burner combo unit, one electric and one butane. I thought it may have been a vent from the pan under the stove, out through the hull. I have to admit that I know nothing about butane though. I know propane settles and the locker needs to be vented to the outside. Our IP had a dedicated propane locker in the cockpit which had a simple hose from the bottom to a vent in the hull.

 

[Peggie Hall HeadMistress]

the fresh water vent should NOT go to the outside of the boat, as any spray or waves could contaminate the tank. it should be vented high INSIDE the boat.

Sorry, no. If that were true, a fuel tank should also be vented inside the boat to prevent spray or waves from contaminating the fuel and we all know that's not even legal! All tanks should be vented to the outside of the boat. Properly installed water and fuel tank vents have a high arch in the vent line that prevents spray or splashing water from getting to the tank and vent thru-hulls designed to prevent it. Venting a water tank into the bilge can result in contamination by bilge odors and associated bacteria ...water overflowing out the vent (who among us has never overfilled his water tank?) or spilling out a vent high in the boat when the boat is heeled can make a real mess in a locker or lazerette.

 

[centerline]

PO could mean the same as PPO.... the previous, previous owner

 

[Capt jgw]

A lot of boats have the water tanks vented inside. Does name a mess if you over fill, but it helps keep the water clean. Obviously a no no for fuel.

 

[Peggie Hall HeadMistress]

I was the 5th owner of my last boat...so I guess that would make the first two PO3 and PO4...

 

[Peggie Hall HeadMistress]

A lot of boats have the water tanks vented inside. Does name a mess if you over fill, but it helps keep the water clean.

I know there are...but contrary to popular belief it doesn't keep the water any cleaner than--or even as clean as--a properly installed vent to the outside. It just saves the builder the cost of one well-above waterline hole in the boat and vent thru-hull.

 

[centerline]

Sorry, no. If that were true, a fuel tank should also be vented inside the boat to prevent spray or waves from contaminating the fuel and we all know that's not even legal! All tanks should be vented to the outside of the boat. Properly installed water and fuel tank vents have a high arch in the vent line that prevents spray or splashing water from getting to the tank and vent thru-hulls designed to prevent it. Venting a water tank into the bilge can result in contamination by bilge odors and associated bacteria ...water overflowing out the vent (who among us has never overfilled his water tank?) or spilling out a vent high in the boat when the boat is heeled can make a real mess in a locker or lazerette.

where do you come up with some of this stuff

fuel tanks and water tanks are so much different...where did the fuel tank vent enter the picture?
there are two opinions here, but one of them does not follow the general practices of people who rig their boat specifically for sailing the oceans (or at least the ones have written books about it)...

if the vent is high and on the center line of the vessel, it will be nearly impossible to splash out the vent, even when heeling.... the vent ONLY has to be there for two reasons. 1 to vent air when filling, and 2, to allow air in to displace the water as its being used.
and if drinking water from the holding tanks, splashes a few drops in to the boat and gets into the bilge, it makes so very little difference and will NOT contaminate the bilge OR the drinking water tank..... no one will even notice. but you are correct that if one likes to walk away from the filler spigot when filling the tank there could be a problem....

but with that thought, lets use your same analogy when filling the fuel tank.... I will agree there is no cure for stupid, so as long as you take the care required there should not be any spills.

it takes a very small amount of seawater to contaminate a freshwater tank. many of the organisms that live in seawater will proliferate in a freshwater tank as well... and the ones that die in the fresh water will be, well, dead and be a contaminate.

fuel on the other hand is very different.. and there are filters in place to separate the water out, and even if the filters clog, it is easy enough to change them out... while drinking fresh water from the water tanks.

 

[Johnb]

"and if drinking water from the holding tanks"

Man you would have to be desperate

 

[Capt jgw]

I sail on Lake Michigan and run my potable water through a filter on the way to the faucet. Our municipal water comes from Lake Michigan and is run through a filter on the way to the faucet. So I guess it doesn't matter much if I get a little lake water in my tanks. But on the salt? Different story all together.

 

[Ralph Johnstone]

where do you come up with some of this stuff

I would suspect Peggy comes up with this stuff based on logic:

1. A water deck fill port is mounted at deck level.
2. An inside water tank vent would have to rise to the level of the outside deck fill OR you would just keep adding water until you flooded the boat. The water wouldn't rise up in the fill hose.

Any way you look at it, you don't want any tank open to the inside of your boat.

 

[centerline]

"and if drinking water from the holding tanks"

Man you would have to be desperate

a lot of people do... maybe one would have to be desperate to drink from your water tank, but like a camper, motorhome or the "water jug" that you obviously drink from, a boat water tank, if its clean and what goes into it is clean, it will remain clean until contaminates are introduced....
but still, even if one only uses the freshwater tank for cooking or washing the dishes, it needs to be FRESH water....

 

[centerline]

Any way you look at it, you don't want any tank open to the inside of your boat.

based on MY opinion, I strongly disagree... some boats set up for ocean cruising are without deck fills to avoid any possible intrusion due to a leaky gasket.... and their vents do NOT go outside either..

but it can be set up however one wants... there is no law that says where the water tank vent needs to be, but it is important that seawater does not get introduced into your freshwater tank.

 

[Capt jgw]

a lot of people do... maybe one would have to be desperate to drink from your water tank, but like a camper, motorhome or the "water jug" that you obviously drink from, a boat water tank, if its clean and what goes into it is clean, it will remain clean until contaminates are introduced....
but still, even if one only uses the freshwater tank for cooking or washing the dishes, it needs to be FRESH water....

"Holding tank" usually means sewage tank. "PW tank" is your drinking water.

 

[Capt jgw]

based on my opinion, I strongly disagree... some boats set up for ocean cruising are without deck fills to avoid any possible intrusion due to a leaky gasket.... and their vents do NOT go outside either..

but it can be set up however one wants... there is no law that says where the water tank vent needs to be....

My boat was originally set up with the fills right on the tanks, under the berth cushions. A real pain to fill dragging the hose through the boat and always managing to leak some. I put in deck fills but had nowhere to run the vents higher than the fills so I ran them overboard. Would rather vent them inside but the hoses would be so long I don't think they would vent properly. No problem so far but like I said earlier I'm on Lake Michigan and wouldn't notice of I did get some lake water in the tanks. The fittings are fuel vents with screens so that keeps the bugs out. I can just stick the hose in and walk away, when I hear the water running out I know they're full. Much easier than before.

 

[Craig Cook]

Two things.
First, a factory photo of the port side of a Hunter 27-3 shows only one vent. Looks like a mistake to me. It will get sealed off.
Second. All this talk of fresh water, fresh water tanks and contamination brings up a time consuming project that I need to take care of as soon as we stop getting freezing temperatures. The fresh water system on our boat is scary. As I have said many times here, the PO didn't use this boat much (70 hours on the clock for the diesel), but didn't maintain it either. My plan is to pull the screens in the system, pull off the shower spray heads, fill the fresh water tank with a water/bleach mix and run it through all the lines. The reason for pulling the screens and shower heads is that everything is filled with nastiness. No black mold or anything like that but definitely a bad case of slimy yick (technical term). I was going to let that sit for a day, then pump it through and do it all over again.

Any thoughts from the group? Is there a better way or a better product than water/bleach???

 

[centerline]

Two things.
First, a factory photo of the port side of a Hunter 27-3 shows only one vent. Looks like a mistake to me. It will get sealed off.
Second. All this talk of fresh water, fresh water tanks and contamination brings up a time consuming project that I need to take care of as soon as we stop getting freezing temperatures. The fresh water system on our boat is scary. As I have said many times here, the PO didn't use this boat much (70 hours on the clock for the diesel), but didn't maintain it either. My plan is to pull the screens in the system, pull off the shower spray heads, fill the fresh water tank with a water/bleach mix and run it through all the lines. The reason for pulling the screens and shower heads is that everything is filled with nastiness. No black mold or anything like that but definitely a bad case of slimy yick (technical term). I was going to let that sit for a day, then pump it through and do it all over again.

Any thoughts from the group? Is there a better way or a better product than water/bleach???

there is always someone who will disagree, but in my opnion, you cant beat the bleach treatment.... do it a bit rich, run it thru all the faucets and lines, then let it set 24-36 hrs...... then open the faucets and run it thru a bit more, and let it set another 24 hours..... then drain the system, flush it with a little bit of fresh water, then refill the tank... preferably thru a filter. it will be drinkable.

 

[Skipper]

Re: fresh water tank vent.
Any cruiser will say to vent the tanks inside.
Offshore heavy seas will penetrate any vent located on the hullsides. The water is precious, and therefore guarded with care.
Overflow is not an issue versus the preservation of water supply. The vents are located high in the cabin, not the bilge. Over filling would just be bad protocol, as with any system.
Practical Sailor also says to vent fresh water tanks inside.