back flushing vent line

[John]

Peggy:
I see from another thread that you recommend back flushing the vent line every time you pump out the holding tank. On my boat (Catalina 36), the vent line is attached to the bottom of one of the stanchions, which has a small vent hole in it above deck. So I guess from what you're saying I should detach the line every time and back flush it. My second question is whether I need to have some pressure in the water going through the vent line. It seems to me that this would require some means of sealing the hose to the line. Another thought: I've cleaned out the line before by simply inserting one end into an "air" horn and giving the horn a blast. Do you think this is adequate?

 

[Peggie Hall HeadMistress]

What you REALLY should do...

Is get the vent line out of the stanchion and connected to a proper thru-hull. (Yes, that means putting a hole in the side of your boat right below the toe rail). That slit doesn't even begin to allow enough air exchange in the tank to keep the contents anywhere close to aerobic--essential to preventing odor...Catalina is one of the few builders who puts vent lines into stanchions, and even they've finally recognized that, while that may be an ok--but not great--location for the fuel and water tank vents, it's horrible location for waste tank vents and have begun running waste tank vents to thru-hulls on most of their boats now. Not only does a thru-hull make vent line maintenance MUCH easier, but it also helps to eliminate the noxious blast out the vent every time the toilet is flushed.

An air horn and any tool you have that will work to scrape out the slit in the stanchion will work, sort of...but you still have remove one end of the vent line to use the air horn...which is a PITB. Plus, waste spills into the vent when the boat heels, and air can't soften any hardened waste in the line to wash it it out. Which means that of course there has be pressure in the water going into the vent line...how do you expect to dislodge anything stuck to the inside of the hose and the tank fitting if there's no pressure?

So make your life much easier--and that of everyone downwind of you much more pleasant...Install a a nice open "bulkhead" thru-hull and move the bloomin' vent line to it.

 

[John]

What do you mean a "'bulkhead'" thru-hull? Are you talking about just a regular thru-hull vent? Thanks. (And yes, you're right, when there's just a little bit in the holding tank, it's not very nice when somebody flushes the toilet unless we're on a broad reach.)

 

[Peggie Hall HeadMistress]

Not a "vent" thru-hull...

They're all one-size-fits-all designed to be used for fuel, water and waste...but a bad choice for waste. What you want is a plain ol' bulkhead or "mushroom" thru-hull that looks like the ones in this photo. If you regularly put your rails in the water for more than a minute or two at a time, you'll prob'ly want to put a clamshell cover over it.

 

[John]

Re: Not a "vent" thru-hull...

Thanks. one last question: Would you recommending using the same hose or drilling a new hole in the tank, installing a new fitting possibly with a larger hose? That way, there would be two vents, possibly helping air to circulate. Also, should the vent hole in the hull be just more or less directly over the tank, meaning the shortest run of hose possible?

 

[Peggie Hall HeadMistress]

Larger diameter would be a great idea...

And thanks to a li'l gadget called the "Uniseal," UNISEAL it's not that hard to put a larger vent fitting in the tank. But it makes to no sense to add another vent line while leaving the original in the stanchion, 'cuz the one in the stanchion won't contribute a thing...it doesn't contribute anything now, and you'd still have all the same hassle of preventing it from becoming blocked that you have now.

So I'd remove that line altogether and put a threaded plug in the tank fitting...then put a new 1" diameter fitting in the tank--this time on the inboard side of the top of the tank...and run it far enough forward to keep the rise to no more than 45 degrees. Use Odorlos according to directions in the tank...backflush the vent and rinse out the tank as previously discussed...and everyone onboard AND downwind of you will be happy.