Rich, Bill - air flow?

[Roger Long]

I had an epiphany while sitting through a long school concert (the last one for this lifetime, at least with my boys' generation):

For the amount of air we are talking about and the consensus that intermediate O2 replenishment is OK, there already is an air pump. It's right on the side of the water closet, at least for manual heads.

When the boat is occupied and in use, flushing will certainly stir the contents somewhat. A few extra strokes after the bowl and lower pipe are dry will pump in some additional air. Just remember and tell guests to give a few extra strokes with the lever in dry position.

The greatest need for additional air would be when the boat is unoccupied for several days or longer; especially if it can't be pumped out right before. The solar air pump would be perfect for that and the noise wouldn't be an issue.

I have an anti-siphon loop between my head and tank.

It's there simply because it was a return bend I could get quickly that had mounting lugs attached. I figured the anti-siphon couldn't hurt helping stuff flow down into the tank and, if I ever had odor, I would just plug it up. So far, no odor. Anyway, it would be an easy matter when leaving the boat to just unscrew it and screw on an adapter for a hose to the solar pump set on deck with the hose running up through the Dorade vent right above.

I'm satisfied now that, if my larger single vent arrangement proves insufficient once I get to warm water next winter, I have some easy to implement options so I'm not going to run a second vent line now.

If I had a clear path to the opposite side of the boat, or to run a vent up to the cabin top where a second vent clamshell wouldn't scoop up water when heeled, I would certainly run a second vent now. I'm sure there are many vessels arranged so that I would advise that course of action.

 

[catsailor]

Hmmm.... I'm not so sure. The need is ~ 4-10 ft3 per day, or about 50 gallons of pumping. I doubt extra pumping would amount to more than 5 gallons of air per day, since a whole flush cycle is no more than a gallon. Also, if there is anything like an odor problem adding the volume all at the same time will increase the surge.

 

[Roger Long]

I doubt extra pumping would amount to more than 5 gallons of air per day, since a whole flush cycle is no more than a gallon.

I'm assuming, based on past performance of my very substandard system, that the larger single vent I am installing will be somewhat effective and hand pumping extra strokes would just be to get the smaller amount of additional air needed. Odor is going to be more of a problem when it's warm. Hot weather means more liquid consumption which means more pumping and opportunities for a few extra dry strokes. Not doing extra strokes after introducing solids is probably a good idea if there is a party going on topside

 

[thinwater]

I'm assuming, based on past performance of my very substandard system, that the larger single vent I am installing will be somewhat effective and hand pumping extra strokes would just be to get the smaller amount of additional air needed. Odor is going to be more of a problem when it's warm. Hot weather means more liquid consumption which means more pumping and opportunities for a few extra dry strokes. Not doing extra strokes after introducing solids is probably a good idea if there is a party going on topside

From my expereince, it makes little differernce what you have introduced, only the volume of pre-existing gases you have displaced.

 

[CarlN]

I've been thinking about the same problem and am leaning towards a small 12v input fan. In this case a 40mm computer fan that draws 0.2 watts and more importantly claims to be 14 DBA at 1 meter. I believe that you can also adjust the RPM down. About $15.

http://www.silenx.com/ixtremaprofans.asp?sku=ixp-11-14

I also noticed in Professional Boatbuilder an ad for charcoal vent filters for the exit vent. These are large diameter PVC so I would hope that they don't offer much if any back pressure (I might get the 3" size and adapt the ends down to 3/4" hose). A little pricey but they seem like they'd last for years and I hate any whiff of holding tank.

http://industrialodorcontrol.com/PROD/WVI.html

Any opinions or guidance?

Carl

 

[RichH]

I've been thinking about the same problem and am leaning towards a small 12v input fan. In this case a 40mm computer fan that draws 0.2 watts and more importantly claims to be 14 DBA at 1 meter. I believe that you can also adjust the RPM down. About $15.

http://www.silenx.com/ixtremaprofans.asp?sku=ixp-11-14



Any opinions or guidance?

Carl

Sewage gases can be explosive, computer fans are no not explosion proof/protected .... BOOM.

 

[Roger Long]

I've been thinking about the same problem and am leaning towards a small 12v input fan.I also noticed in Professional Boatbuilder an ad for charcoal vent filters for the exit vent.

There was just a thread on filters http://forums.sbo.sailboatowners.com/showthread.php?t=127608 you'll probably join the consensus to forget about them when you read it. To quote Rich on computer fans, "BOOM", that says it all.

 

[CarlN]

Thanks - I'd missed the thread on filters. Oh well...

And the fan seems less interesting now too. I'd imagined using it to push fresh air in rather than pull sewage gas out, but there's no reason to believe that the gas would always follow instructions. Could be one of those low probability/high consequences situations.

 

[FourPoints]

The solar cell from this 10 buck Home Depot fence light will run the air pump on a partly cloudy Maine mid afternoon. It doesn't quite have enough umph to start reliably after a cloud goes across the sun however. Two cells in parallel should run it fine.

I just completed a similar type modification of a $2 LED walkway light I picked up at Target to power a windex light. As soon as I install it I'll post some pictures to a new thread.

 

[thinwater]

There was just a thread on filters http://forums.sbo.sailboatowners.com/showthread.php?t=127608 you'll probably join the consensus to forget about them when you read it. To quote Rich on computer fans, "BOOM", that says it all.

I don't know... I see way to many OEM installations and too many happy owners to call that a consensus or to see a consensus elsewhere. I believe the ball must remain in play.

 

[Bill Roosa]

So Roger, you had a conversation with Peggy and I gather she is of the opinion that your twin vent arangement would work as is. So what problem are we trying to solve here?

 

[Roger Long]

So what problem are we trying to solve here?

I can't install that vent system on my boat. I have immovable things like molded in fresh water tanks in the way. My boat also operates at enough of a heel angle that a forward facing clamshell vent would fill up the holding tank in about 10 minutes going to windward in a breeze.

Since the ideal system shown in the OP produces an air flow proven to work, I'm trying to figure out how to duplicate that air exchange performance with the means practical for installation in my boat. That unfortunately means some sort of powered input of air. I expect many people will be facing a similar situation which is why I'm discussing it here.