Back flush vent line

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.

rusbet

Veteran Member
Joined
Oct 1, 2010
Messages
63
How do you identify the holding tank vent line opening on the outside of the boat? (by smell?)

What are the steps to back flushing the vent line? (My impression is to stick the water hose to the vent line opening and turn on the water full blast for 5 seconds)

If there is an obnoxious smell everytime we pump-out, what should we be doing (with clear instructions)

Many thanks!

*
 
Do not backflush the fuel line by mistake
 
rusbet wrote:
How do you identify the holding tank vent line opening on the outside of the boat? (by smell?)

What are the steps to back flushing the vent line? (My impression is to stick the water hose to the vent line opening and turn on the water full blast for 5 seconds)

If there is an obnoxious smell everytime we pump-out, what should we be doing (with clear instructions)

Many thanks!

*
*I wouldn't flush it with liquid, if there is a low spot in the line the water will sit there and basically block the line. What area is this smell coming from and how are you pumping out?
 
rochepoint wrote:rusbet wrote:
How do you identify the holding tank vent line opening on the outside of the boat? (by smell?)

What are the steps to back flushing the vent line? (My impression is to stick the water hose to the vent line opening and turn on the water full blast for 5 seconds)

If there is an obnoxious smell everytime we pump-out, what should we be doing (with clear instructions)

Many thanks!

*
*I wouldn't flush it with liquid, if there is a low spot in the line the water will sit there and basically block the line. What area is this smell coming from and how are you pumping out?

We have a waste deck fitting and the pump-out hose is attached and is then turned on by the deckhand. We purchased an adapter so the fit is good.* The smell lingers near the waste deck fitting for about 30 min.*
 
On my Monk, a 2003 model, one can trace the Holding tank vent hose back to the tank I can reach it through the stbd door steps. The hose goes through a hole to the engine room and down to the tank. It is not well routed, it has lots of curves and low spots I intend to replace the vent fitting with one that can be backflushed (a mushroom head thru hull) and re rout the hose to eliminate the low spots.
Steve W
 
rusbet wrote:
How do you identify the holding tank vent line opening on the outside of the boat? (by smell?)

What are the steps to back flushing the vent line? (My impression is to stick the water hose to the vent line opening and turn on the water full blast for 5 seconds)
If you can trace the vent line, that is obviously the best way to find the through hull.* If not, it is usually a fairly small opening. On our boat it is down near the waterline.* And yes, smell can help you determine if the opening is the tank vent.

We flush the vent line for each holding tank by spraying water into the through hulls and listening for the sound of water going into the tanks.* The configuration of the vent lines runs is such that water will not become trapped in the line when we do this.* But Mike's comment is well heeded.* Make sure there are no low spots in the line that could hold water and block the line.


-- Edited by Marin on Saturday 31st of December 2011 02:13:29 PM
 
The first thing to do is buy Peggy Hall's book "Get Rid Of Boat Odors" and read it. The better the air circulation in your tank the less the smell. You are on the right track. Follow the hose and make sure there are no low spots, flush the vent often and install a mushroom type thru-hull instead of a covered vent to make it easy to flush. One way to locate the vent would be to put water down the pump out deck fitting, then listen or feel for air coming out of near by vents.
 
"How do you identify the holding tank vent line opening on the outside of the boat? (by smell?)"

No...by finding the other end of it on the tank and tracing it to the hull.*

Which I'm well aware may require contortions that some of us haven't been capable of doing for at least 20 years.* However, there are exercises that will make it not only possible again, but actually EASY again, at least, for most of us. * Make a resolution to start doing 'em!
biggrin.gif


Happy New Year, y'all!
 
When you see a dribble of liquid running down the hull from the outlet fitting, taste it. You will know instantly. I know someone who used this method!
 
Oh yuk!

Tracing vent lines to their thru-hulls really isn't that hard to do...'cuz there aren't very many--holding, fuel and water.

As for any concerns about backflushing the line leaving water sitting in a low spot, the solution to that one is simple: eliminate the low spot. 'Cuz backflushed water isn't the only thing that can leave water pooled in it...'condensation...spillage from an over-full tank are just two that come to mind. You can't back flush the vent if there's a filter in the line (which IMO is one of the reasons to get rid of the filter!). However, insuring that it never becomes blocked is essential preventive maintenance...and the easiest way to do that is to back flush it every time you wash the boat and/or pump out the tank. Some vent thru-hulls make it impossible...but there's a simple solution to that too: replace the "vent" thru-hull with an open bulkhead thru-hull...which will also help to keep the tank aerobic by allowing more air exhange.
 
koliver wrote:
When you see a dribble of liquid running down the hull from the outlet fitting, taste it. You will know instantly. I know someone who used this method!
*Taste it?! what if it's diesel!

Steve W
 
HopCar wrote:
The first thing to do is buy Peggy Hall's book "Get Rid Of Boat Odors" and read it. The better the air circulation in your tank the less the smell. You are on the right track. Follow the hose and make sure there are no low spots, flush the vent often and install a mushroom type thru-hull instead of a covered vent to make it easy to flush. One way to locate the vent would be to put water down the pump out deck fitting, then listen or feel for air coming out of near by vents.

I second the rcommendation to buy the book.* Study it, then you can answer, rather than ask questions.
smile.gif


Now - yes, you can pour water down the deck fitting and feel for air movement.* Or, have someone flush the head.* Same thing, air will come out.* And, there may be an identifying odor as well.

Now - are you sure you want to backflush the vent line?* On many boats, there is a charcoal filter in the vent line.* If it gets wet, it's ruined and it will block the vent.

Taking a*page from Peggy's book, find the filter, remove it, insert a piece of hose in it's place, and toss the filter in an appropriate place where it will find its way to the landfill.
*



-- Edited by rwidman on Monday 2nd of January 2012 12:05:23 PM


-- Edited by rwidman on Monday 2nd of January 2012 12:14:21 PM
 
Still haven't found the holding tank vent fitting? It's probably near the deck pumpout fitting. It's usually as close to the actual holding tank as practical. And it's high up on the hull side. Anything down low is a drain.

You will have a vent for every tank. Potable water, fuel, and holding tank.
 
rwidman wrote:
It's probably near the deck pumpout fitting. It's usually as close to the actual holding tank as practical. And it's high up on the hull side. Anything down low is a drain.
Not necessarily.* It will depend on the make of the boat.* Earlier Grand Banks for example-- and perhaps later ones, too--* have their holding tank vent through-hulls in the side of the hull just above the waterline.* Not only are they low, but they are nowhere near the pumpout fitting.* The location of these components varies greatly between manufacturers.


-- Edited by Marin on Monday 2nd of January 2012 01:46:02 PM
 
Marin wrote:rwidman wrote:
It's probably near the deck pumpout fitting. It's usually as close to the actual holding tank as practical. And it's high up on the hull side. Anything down low is a drain.
Not necessarily.* It will depend on the make of the boat.* Earlier Grand Banks for example-- and perhaps later ones, too--* have their holding tank vent through-hulls in the side of the hull just above the waterline.* Not only are they low, but they are nowhere near the pumpout fitting.* The location of these components varies greatly between manufacturers.



-- Edited by Marin on Monday 2nd of January 2012 01:46:02 PM

No doubt it varies by manufacturer but best practice would have both be a short and direct as practical.

*
 
Steve wrote:koliver wrote:
When you see a dribble of liquid running down the hull from the outlet fitting, taste it. You will know instantly. I know someone who used this method!
*Taste it?! what if it's diesel!

Steve W

*

If you taste it and you find it was the holding tank you will wish it had been* Diesel!

HOLLYWOOD
 

Attachments

  • 300px-bad_taste.jpg
    300px-bad_taste.jpg
    34.3 KB · Views: 101
"

"If you taste it and you find it was the holding tank you will wish it had been Diesel!"


Due to a nasty shower I received while pumping out one Sunday morning in Clearwater a few years ago I do know the taste of holding tank contents, you are right I'll take diesel any time.
Steve W
 
Thanks everyone for your input. It has been very helpful. We'll search out the right vent opening and do the necessary. I'm still not clear on how one actually backflushes and for how long but I'll assume it is just shooting some water into the vent opening with the non-potable water hose.
 
rusbet wrote:
I'm still not clear on how one actually backflushes and for how long but I'll assume it is just shooting some water into the vent opening with the non-potable water hose.
That's what we do.* We put a plastic squirt nozzle on the end of the washdown hose and shoot water into the vent through-hull.* However I would suggest that when you do this you have someone near enough to the holding tank to confirm by hearing it*that your backflush water is, in fact, going into the tank.* That way you'll know for sure*that the vent line is clear.
 
First, make sure there's no vent filter before you decide to back flush your holding tank vent line. If there's a filter, you will ruin it and block the vent.

Second, if there is a downward loop in the vent line (there shouldn't be), backflushing may leave enough water in the loop to block the vent line.

And of course, be really sure you are shooting water into the holding tank vent, not the potable water or furl tank vent.
 
Back
Top Bottom