Holding tank vents through stanchion?

[Jim]

My holding tank is building up pressure during use and I figured it wasn't venting properly. I found that the venting hose seemed to clogged with no ventelation...I followed it and it is attached to the bottom of a stanchion in a spot behind the head medicine cabinet that I can't get to without removing the medicine cabinet. BUT, I'm looking at the stanchion above decks and there is no sign of a vent hole!? The holes the lifelines go through are sealed with tubes. Any ideas? Could the base be clogged? Should I drill a hole in the stanchion?Thanks to all,Jim

 

[Peggie Hall/HeadMistress]

You must have a Catalina...

I know it's a lot of work, but I'd reroute the vent line to a thru-hull. You don't even have to remove the existing hose...just disconnect it from the tank fitting, cut off as much of it as you can reach and stick a plug in the end of it. Then run a new vent line off the tank to a new thru-hull. The only hard part will be drilling a new hole for it.

 

[Gary]

There is a hole

On my 1990 C-30 there is a small hotel drilled at the bse of the stanchion, oriented overboard. If you had no hole at all you wouldn't be able to pump anything to the holding tank because the pressure would build up. There are similar holes in the stanchions on the starboard side for the water tanks.

 

[Peggie Hall/HeadMistress]

Gary, the problem is...

The tiny hole in the stanchion doesn't permit enough exchange of air to keep a holding tank aerobic--which is why Catalinas "gas" everyone in a 50' radius every time the head is flushed, and sometimes even when the boat rocks. It's fine as a water or fuel tank vent, because neither water nor fuel are organic matter which produce gasses as it breaks down.For a full explanation, read the article "Odor Control in Holding Tanks" in the HM Reference Library...but in a nutshell: when any organic matter breaks down aerobically (iow, in the presence of oxygen), it converts to CO2, which is odorless...but when any organic matter breaks down anaerobically, it ferments, producing sulphurous gasses that stink. The same principles are at work in a holding tank that are at work in a compost pile, a pond, or the human body: oxygen keeps it healthy and odorless, a lack of oxygen creates unhealthy septic putrification that stinks. It's biology 101.