where's your holding tank vent?

Vikings,

Where are your holding tank vents? I'm trying to figure out where to install mine. I'm thinking of putting the through-hull (or hulls) just beneath the sheer stripe, but I'm a little concerned about water intrusion. I've found two links that show two different approaches. Thanks for any suggestions and/or pictures.

Roscoe
E25, #226

http://svrainshadow.com/?p=315

http://www.thevirtualboatyard.com/2009/03/holding-tank-vents-revisited.html

mine is through the hull just under the rub rail/ hull deck joint. its a lil clamshell vent

I put the Vent filter behind the lav sink mounted to the counter and ran the thru hull straight out just below the rub rail. Edd

Factory vent outlet for out boat was at the top of the transom, same side of the boat as the H.T.
Be sure that the vent hose has no sags in it to every hold "liquid."
For that matter, also be sure that you do not over-fill the tank so that there's any threat of getting anything in that hose!


LB

Ours is on the port side (same side as holding tank) just below the rubrail about in the middle of the blue stripe, with a vent that has a small screen and faces aft/slightly down to minimize water/rain intrusion. Remember that Peggy Hall and others suggest that the vent hose not be too small so that it will allow oxygen/air flow to minimize odour--I think she suggests 5/8 or even 3/4" rather than the customary 1/2" She also suggests a vent on either side to allow cross-flow. I don't have that, and I still don't get any real odour from the head/holding tank.

You might want to have the hose run slightly uphill rather than downhill in case the holding tank overflows--uphill would drain any effluent back into the tank once it's emptied.

Frank

Frank Langer said:

Ours is on the port side (same side as holding tank) just below the rubrail about in the middle of the blue stripe, with a vent that has a small screen and faces aft/slightly down to minimize water/rain intrusion. Remember that Peggy Hall and others suggest that the vent hose not be too small so that it will allow oxygen/air flow to minimize odour--I think she suggests 5/8 or even 3/4" rather than the customary 1/2" She also suggests a vent on either side to allow cross-flow. I don't have that, and I still don't get any real odour from the head/holding tank.

You might want to have the hose run slightly uphill rather than downhill in case the holding tank overflows--uphill would drain any effluent back into the tank once it's emptied.

Frank

Click to expand...

One other thing Peggy Hall recommends is that the angle of the vent line be no steeper than 45 degrees above horizontal. Apparently steepness makes it harder for the air to flow freely, hence impeding the ability of oxygen to do its work on the bacteria. For people who want to have their tanks down low this can create design problems.

Forward Port Side

If you take a look at my album, you can just make it out on the port side of the hull. Look directly below the forward port window.

Vent

Roscoe,

Mine was directly above the head on the cabin side with the 1/2" hose. I filled it in w epoxy and not sure if a marine head or porta potty is going back in or not.

Scott
1973 E25 CB

Summary of results so far: 3 owners (Zube, Edd, and Frank) have vents just beneath the rub rail (thus within the sheer stripe area), one (Todd) has his vent just beneath the sheer stripe, one (Scott) has or had his on the side of the cabin, and one (Loren) has his on the transom.

I've read quite a few of Head Mistress Peggy Hall's postings on other forums. She recommends that the vent be mounted just beneath the rub rail (thus, for Ericsons that means within the sheer stripe area). She also urges that clamshells be used to protect the through-hulls from water intrusion. What I'm having trouble with, however, is how one is to make her advice on the location of the vent through-hull correspond to her advice on the length of the hose and the routing of the hose. From what I can tell, most Ericson owners mount their holding tanks somewhere in the vicinity of the head, which usually means in a compartment under the V Berth. By my calculations, I need a run of at least six feet from the holding tank to the vent, if I put the through-hull at the sheer line. This is a long run by Peggy's standards. This run will also require me to make at least one 90 degree turn from the compartment up the side of the hull. It will also, accordingly, require a vertical rise. This also violates the advice she frequently gives. There really seems to be no way around running the hose as I have described. It's either that or mount the holding tank on the settee in the main salon. That would be a pretty sight, wouldn't it? Here's my explanation to my guests, "well at least the damn thing doesn't stink!"

Roscoe

Tank vent hose.

All, I'm sort of kidnapping this thread to share something with you regarding the vent hose and hull fitting for my diesel tank, I know, I know, that's not what you're discussing but something Roscoe wrote about brought my vent arrangement to mind. First of all, I recently installed a fuel whistle in the vent line: http://www.greenmarineproducts.com/products.html At the same time I was installing a fine old vintage, bronze Wilcox Crittenden vent fitting, I took the opportunity to add a 45° brass elbow to the threaded end of it that pointed up into the hollow of the coaming. By the time I'd installed a barb in that, the hose had an arc that was at least 6" above the vent itself. So I figure with that loop in it along with a small bit of bronze screen in the vent fitting itself, that might significantly reduce the possibility of sea water sloshing down the hose and into the fuel tank. I now return you to your original thread. Cheers, Glyn Judson, E31 hull #55, Marina del Rey CA

No problem Glyn about the digression on your fuel line. Your words about the 45 degree elbow gave me the idea that perhaps I should use something like this in the lower portion of the hose as it runs from the V Berth compartment. This would prevent a sharp 90 turn and also any kinking that might occur over time. As far a putting that 45 degree elbow up in the coaming, so as to reduce the risk of water intrusion, Peggy Hall says that this is not good (for a holding tank vent), since it impedes the free flow of air. I read this in one of her postings yesterday morning, and can seem to find the thread again among the thousands out there. At any rate, she specifically advised a guy to remove this very type of set-up. It's just her opinion, but everyone out there seems to bow in joyful obedience to the Head Mistress.

As I was looking around, trying to find that thread by said Head Mistress, Peggy Hall, I came across this online article from SAIL magazine. There's a good picture of a through-hull vent at about the sheer stripe level. The guy mounted the holding tank high-up on the hull to achieve Newtonian discharge. This enables him to have a very short vent hose run (such as Peggy Hall advises). He does, though, install a loop of sorts in it (sort of like Glyn describes) to prevent water intrusion.

http://www.sailmagazine.com/boatworks-projects-systemsengines/gravity-theory

Due to size contraints, I, and I suspect many others, are unable to have such a setup. One thought I do keep coming back to is the approach made by Capt'n Pauley. His diagram shows two vent lines being criss-crossed to opposite sides of the boat so as to prevent water intrusion. This seems to solve the water intrusion problem, but it also brings with it even longer runs of the hoses, which runs counter to the advice of the Head Mistress.

http://www.thevirtualboatyard.com/2009/03/holding-tank-vents-revisited.html

I suppose the old dictum about sailboats in general holds true here . . . everything is a compromise.

Roscoe