vent hose

[Don Crowther]

I need some help with the vent hose off the septic tank.
When I was installing the tank i found the hose to have split about 3 inches from the tank. It was also split near the thru-hull The hose is probably 30 years old so it doesn't owe me anything.
I couldn't find the same type of hose here so i've bought something close. It's wire filled so it'll bend but I'm not sure I can get the full 180 in the tight spot in the head.
Has anyone found another way of installing the vent hose? Or what else could I try? Does it need to be bent 180. We rarely have the boat heeled over as far as the thru-hull.
Pictures are always good.
Thanks

 

[splax]

I am sure that anti-siphoning measurer is necessary. No one wants sewage coming up out of the toilet and in addition sinking your boat. A 360 coil-loop might be easier to do. I haven't yet replaced that hose.

 

[Peggie Hall HeadMistress]

]I need some help with the vent hose off the septic tank...I couldn't find the same type of hose here so i've bought something close. It's wire filled so it'll bend but I'm not sure I can get the full 180 in the tight spot in the head.

Don't even THINK of trying to bend any hose 180. However, there shouldn't BE a 180 in a holding tank vent line...or even a 90. The waste tank vent line needs to be short and straight--NO bends is ideal, but not always possible 5/8" flexible PVC #148 is the right kind of hose for the vent line...Shields or Trident if you can get it in Canada. If the rest of your hoses are as old as the vent line, they should ALL be replaced if you don't want a split to dump a tank in your boat...you've seen what age does to hose.

Or what else could I try?

You might consider picking up a copy of my book from the online store here (see link in my signature)...it's a comprehensive "holding tanks 101" manual that should help you get it right. And I'm alwasy glad to answer questions via email.

Does it need to be bent 180.

Doesn't need to be bent at all...the minimum needed to get directly from the tank to the thru-hull.

We rarely have the boat heeled over as far as the thru-hull.

If you're concerned about that, put a clamshell cover over the thru-hull.

 

[Don Crowther]

Thanks Peggy
I've got your book but I didn't go to it!!
The hose I took off had a 180 bend at the thru-hull so I was just copying what someone else had done.
So you're telling me I don't need a bend in the vent hose just hook it straight up to the thru-hull?

I've put new hoses on all the other lines just didn't think the vent was that important. After all no waste travels through just air right?
Thanks

 

[Bill Roosa]

That bend was probably so you can get assess to it or to keep the hose from kinking. While you don't need any bending to vent the tank you might need it to actually route the hose.

 

[Bill Roosa]

As for anti-siphon on a vent that seems pretty unlikely. You would have to be heeled over for quite some time, the vent would have to be somewhat forward in the boat so ram pressure water could start the flow. If the water flow is perpendicular to the thru hull the Brunillie effect causes a suction in this case out of the tank.
SOOOO you fall asleep for several hours while the boat is heeled way over and the boat fills with water and slows down and rights itself....... Don't think anybody has ever sunk a boat this way

 

[Don Crowther]

It's just funny that both vent lines have that 180 bend right at the thru-hull. I'm not even sure where the second line comes from it disappears under the floor.

As for falling asleep when the boat is heeled over that far that would never happen.

 

[Peggie Hall HeadMistress]

The hose I took off had a 180 bend at the thru-hull so I was just copying what someone else had done.

I have a photograph of vent line with a full 360!

So you're telling me I don't need a bend in the vent hose just hook it straight up to the thru-hull?

Correct...and if you'll read the chapter "Holding Tank Odor--Odor Out the Vent" you'll know WHY the vent line needs to be as short, straight...and as horizontal too--as possible.

I've put new hoses on all the other lines just didn't think the vent was that important. After all no waste travels through just air right?

Theoretically, but not always. But even if only air does pass through a vent line, you don't want the nasty gasses to vent inside your boat.

FYI, the average useable life of ANY hose--waste, water, fuel, exhaust, and vent too--is about 10 years, because (as you've seen happen to your vent line), ALL hoses, nylon, plasitic and rubber, dry out and become brittle over time, which causes 'em to crack and split. Yours were 30 years old...and so are any of the remaining original hoses in all the systems on your boat....all overdue for replacement, especially those connected to below-waterline thru-hulls.

Bill said, While you don't need any bending to vent the tank you might need it to actually route the hose.

If you have to put a 180--or even a 90--or any bend that isn't a very gradual sweep in a vent line to route it from the tank to thru-hull, either the thru-hull or the vent fitting on the tank--or both!--need to be moved!

Splax said: I am sure that anti-siphoning measurer is necessary.
No one wants sewage coming up out of the toilet and in addition sinking your boat. A 360 coil-loop might be easier to do.

A vented loop may or may not be called for in the head discharge line--and definitely in the head intake line to any toilet that isn't well above the waterline--but never in a tank vent line. Vent lines only go to thru-hulls...no way that waste can come back to the toilet through the vent...no way that water entering the boat via the tank vent (which is almost impossible unless you're "submarining" in heavy seas for days at a time and can be prevented without any bends or loops in the vent line) can sink a boat.

 

[Don Crowther]

Ok thanks everyone.
I think I got it. Straight line, small turns.

 

[splax]

Well, I stand correctly informed ! I considered the original design and the only reason I thought might be a loop to prevent water flowing into the tank, possibly forcing other material up through the toilet. The term anti-siphoning was an inaccurate use of a technical term, and I'm caught. I need to get that book !