[UltimateWalrus]

I'm now planning on trying to install an Air Head on my boat, and forego the nightmare of trying to retrofit it with a holding tank. The only thing I need to worry about now is installing a vent.

I talked a little with Air Head support and they recommend using a 2 1/2" ventilation hose and thru-hull, the kind that usually has a vent cowl on it.

My boat already has one of these vent cowls for the engine compartment fan (only needed when there are gas fumes or the boat smells for some other reason). So I thought maybe I could combine the systems with a Y-connector and not have to drill any new holes through my hull, which would be really beneficial in that it will be less work, won't change the boat cosmetically, and won't be as permanent if I need to try something else.

Does this setup raise any red flags for anyone?

I think I can protect the engine (and my cabin) from backwash from the Air Head fan, by just placing a simple air valve in the engine vent hose. However I was also wondering where I might find a simple air valve like that. All the ones I can find online are for inflatable boats. If they made any that are threaded, or at least have tubed ends that I can clamp something onto, that'd work much better.

Or I guess there's always duct tape...

EDIT:
Sorry!! The problem has been solved.

I dunno how I could've been such a blockhead. I thought I only had one of these.

There's two. One on each side. And the starboard one doesn't even do anything. Pretty silly that I missed something so huge and obvious. In my defense, this is my first boat :]

 

[Gladrags1]

Let me guess - the port side is connected to a blower to remove air from the engine room? If so, the starboard is for air intake to suck fresh air into the engine room.

Tod

 

[UltimateWalrus]

Oh! I hadn't considered that. I'll have to double check. The engine compartment isn't airtight so I figured the suction would work without an intake. I'm still inclined to repurpose the starboard vent, though, in a nonpermanent way if I can.

I suppose I could easily test just by blocking the starboard vent and seeing if an adequate amount of air still comes out of the port vent when I turn the blower on.

 

[mitiempo]

Gladrags is correct. You need 2 vents, one for intake air and the other an output from the fan. They have to be dedicated to that use. A surveyor wouldn't pass what you plan to do nor would the Coast Guard if you have a gasoline engine.

 

[UltimateWalrus]

Thanks for the info! I did not know this at all. I guess I'll have a choice to make whether to drill a hole in my hull or not... I'm currently using an outboard as the Atomic 4 inboard needs work, but would like it to be useable again eventually. And I might need to pass a survey as I'm trying for liveaboard status.

I just wish there was a way around drilling a hole in the hull. Feels as if I'm disfiguring my boat. Maybe if I shoot to drill it in the transom, it won't be so bad.

 

[mitiempo]

Where is the head installed? I would put the vent in the same area, maybe in the cabin top above the head.

 

[UltimateWalrus]

The head is on the starboard side next to the v-berth. I don't want people on deck tripping over the vent so I'd be more inclined to drill through the topside.

I actually doubt that smell will really be too much of an issue with the composting toilet. But I can't help but second-guess it, because if I put the vent there and there is a smell problem wafting into the cabin, I can't un-drill the hole. Drilling through the transom might require ~12' of hose but seems less likely to be a decision I regret.

 

[mitiempo]

By topside do you mean the hull? I would avoid that as when sailing it could become an intake. On a powerboat yes but not on a sailboat.

I would install it on the cabintop above the head. Best location to keep water out.

Looks like there is plenty of room on an E29 cabin top for a small vent.

 

[UltimateWalrus]

That's a very good point... it would be very bad to have a hole there on a heel. I just have a safety concern with drilling through the deck, as someone could trip over it and fall overboard, especially with the limited deck space on my 29-footer... not to mention the cosmetic impact. What about drilling as high as possible on the transom? The exhaust, bilge, and gas tank vent thru-hulls are all lower than that anyway.

Or, there is a bit of room behind the starboard vent I showed in the picture. Perhaps I could just drill a new vent directly next to it? If I put another cowl on the new vent, would making the old intake cowl slightly less aerodynamic be any sort of concern?

 

[mitiempo]

I would take a short route, not run it all the way to the transom. If you use the transom you need a high loop in the hose so water cannot enter.

Another solution would be the cabin side near the head.

 

[mr_f]

Where is the deck fitting for the pump-out of your soon-to-be removed holding tank? When I was considering going to a composter, I was planning on repurposing/modifying that already existing hole in my boat for the vent fan. Mine was (as most are) way off to the side of the deck, under the lifelines, and a mushroom cap vent cover struck me as no more of a tripping hazard than the dock cleats and such that are located in similar places on a boat.

EDIT: I just realized that you had posted in a previous thread that your boat never had a holding tank. So my thought isn't worth much to you. Carry on. Nothing to see here.

 

[UltimateWalrus]

No worries, I still appreciate it. Ultimately I think I will run it to right behind the engine intake vent (if there's room) not only for safety but also as a matter of personal taste. The Air Head rep said that 12' of hose would not be too bad as far as the functionality of the toilet goes.