Holding tank vent

[Nereussailor]

How does a holding tank vent work? I was trying to figure it out the other day, and mine doesn't seem to be working properly. I hooked a new hose up to it and tried to blow through it, and I couldn't. I tried to suck on it, and I cold, but barely. Is there a way to clean them out, or should I just replace it?

Dave

 

[Tim R.]

The vent hose should be connected to the top of your holding tank and go to a vent fitting that goes thru the deck or top of the hull. This has to be high enough to not let anything drain out even while heeled. Mine is right under the deck/hull joint. Make sure your vent fitting has screens as spiders like to make nests in them if they can get in.

Replace the hose and check the vent fitting and replace if necessary.

 

[Ed Schenck]

You sucked on the vent hose?! Yuk, that could give you a nasty surprise. You don't say how full your tank is. You do say that you hooked up a new hose. Do you mean directly to the tank connection? Pressurizing the vent hose would be hard. Where would you expect the air to go? If the tank is empty then you would get some air in before it pressurized. The air might go out the inlet to the head depending upon how your valves are set. What you are experiencing in other words could be normal.

 

[Peggie Hall HeadMistress]

I'm guessing you have a blockage...

'Cuz tank vents are totally open...no check valves. The two most common locations for a blockage are the vent thru-hull and the connection to the tank--both the tank fitting and that end of the vent line...but you can't rule out a kink in the line or vent line filter that's failed.

So first step...inspect. If the vent line looks ok...check the thru-hull...dirt daubers love to build nests in 'em, so scrape it out with a screwdriver blade or whatever works. If there's a screen in it, knock it out, 'cuz screens cause more problems they solve or prevent. When you're sure the thru-hull is clean, pull the vent line off the tank and clean out the fitting and that end of the hose.

It's VERY important to keep the vent clear, 'cuz it provides an escape for air in the tank displaced by incoming waste--otherwise flushing the toilet would pressurize the tank...the whole system, actually, with consequences you won't like!--and also provides a source of air during pumpout, without which the pumpout would pull a vacuum which would prevent anything from being pulled out and can result in a cracked tank. So once you've made sure the vent is clear, keep it clear by backflushing it every time you pump out and/or wash the boat.

I suggest you also spend some time reading the discussions in this forum.

 

[Ed A]

Read peggys book

If you want to really understand your sanitation system and avoid problems buy a copy of peggy halls book on this site.]

It is a world of information, more than any of us thought about heads and tanks ect. It is Always on my boat!

 

[Nereussailor]

I tried to poke out the fitting, but it's a 90 degree angle so it's not the easiest to get something up in there. I tried a screwdriver and a piece of wire that wasn't stiff enough. I'll have to find another piece of wire that's a little stiffer and try that. It's plugged with something.
The hose to the tank is brand new, I just installed it, and the tank fitting are all wide open. It's definitely in the through hull fitting.
And yes there are consequences that I don't want to happen. I'm also betting that the leak that I posted in another post could be part of the pressurizing of the tank. Thanks for the advice everyone.

Dave

 

[John]

I had the same problem. I simply removed the end of the hose attached to the tank and put my air (gas, really) horn on it and gave a few blasts. It cleared it up completely.

 

[navigator97]

Another way to clear is to take the hose of at the connection to the tank . Put a hose to garden hose adaptor in to the bottom end of the hose. Connect a garden hose to that adaptor (assuming you will be at a dock with water available) and turn on the water. This should force out anything blocking the vent hose. Water will come out the hull vent fitting. When running clear, shut off water and reattach the vent hose to the tank.

I used that method a few years ago when I had a blocked vent line to my fresh water tank. It wokked well.

Dick
S/V Puffin, H-33.5

 

[Ron20324]

On the thru-hull fitting, on the outside, reach in with a pair of needlenose pliers and yank that screen wire out. Junk will probably come with it.