Holding Tank Vent

[c130king]

Another issue from today was getting my holding tank pumped out. I flushed a few gallons through the head to flush out the hoses. When I opened the pump out deck filling it was very pressurized...think geyser eruption.

Second time I have had this problem.

Also when pumping it out I get loud "sucking" sound in the head as it sucks air through the joker valve. At least I think that is what is happening.

So I suspect clogged holding tank vent valve.

How do you check for this and how do you "un-clog" this vent?

I thought I had asked this question before but I can't find the older thread. Apologies if this is a recent repeat.

Thanks,
Jim

 

[Tom J]

I don't believe there is a vent valve as such. There is a screen under the cap of the vent itself, I think. Definitely sounds like the vent is blocked somewhere. Any chance the hose is kinked or something?

 

[c130king]

Could be. Hard to see it easily as I have an A/C unit with lots of ducting sitting on top of the tank. Will dig around there next week.

Once I figure out which vent is the holding tank can I spray it with the hose to maybe "unclog" it?

Thanks,
jim

 

[Calif. Ted]

On my 320 the tank vent is a black plastic cap that exits the hull below rubrail above the tank I think your boat is the same. The black cap unscrews so you can clear the small passages of the cap and flush the hose.

 

[c130king]

Ted,

No vent on the port side other than the bilge pump outlet. I assume...but don't know for sure...that it was one of the 3 vents on the stern port side.

Once I move all the A/C ducting I will be able to trace the hoses coming off of those vents.

Cheers,
Jim

 

[Tom J]

My vent is in the same location as yours. Best to trace the hoses as you mentioned to determine which one is holding tank.

 

[MarkZ]

The fuel tank vent and holding tank vent are both on the port side of the transom and from the factory they are both the same type fitting (fuel vent fitting). Spiders like to build a nest in the fitting. First thing to do is pull the little screens out of the holding tank vent fittings, because they serve no purpose in this application but collect a lot of debris causing blockage. What I do to keep the vent clear is I use the water hose to run water over the vent while the pump out is vacuuming. The vacuum of the pump out draws water through the vent line which rinses out the debris.

 

[c130king]

Mark,

Great idea. Will give that a try.

Cheers,
Jim

 

[c130king]

Figured out which vent was for the holding tank. Pretty straight forward since there are only 2 vents and one has white hose and one has black hose. And there is a white hose coming off of the top of the holding tank.

It is the bottom vent. And in the close up you might be able to tell that it is fairly corroded. Appears to be small screen elements inside the two openings. Both appeared to be corroded. Was not able to pull them out but was able to poke holes in both of them...very easy to do.

Then sprayed high pressure hose water into those 2 openings. Hopefully that got the vent working again.

Later this week will pump the head to fill (and possibly pressurize) the holding tank full again and then do a pump out and see if I get the geyser again.

Cheers,
Jim

 

[Tom J]

Careful. The top vent is for your fuel tank. Don't want any water getting in there!

 

[c130king]

Dohhhh!!!! Didn't think about that...

 

[mfarinas]

I had the same problem two years ago. Did not realize all that pressure in the holding tank would come out once the deck fitting was removed! I tried to unscrew it slowly, but the pressure finally did it for me. I had the geyser shower all over me and the stern of the boat. What a mess!!!
My solution to the clogged holding tank vent was spraying chlorine bleach right into the vent from the back of the boat. It took a couple of tries, but finally freed the goop.
Now I simply spray it once or twice each year.
Good luck!

Manny Farinas

 

[c130king]

Thanks. Will give that a try. I haven't emptied the tank since I cleared up my vent...at least I think/hope I freed up the vent.

Cheers,
Jim

 

[Pat]

I've had holding tank venting issue the last two years.....so for the short term when I get to the pump out station at our club, I disconnect the vent hose from it's point of attachment to the exterior vent fitting (where it comes thru the hull just below the deck)
and pump it out with the vent hose disconneced...works like a champ....mine is plugged at some point but it must be inside the hull fitting which is a black rubber vent on my
boat...at any rate, the pump out goes great as long as I have disconnected the hose...in other words it is getting it's air flow into the tank from the static air in the cabin, on top of the hanging locker...there is no smell in the boat as air is being sucked out, not in.

 

[c130king]

I am very happy to report that my "fix" to the holding tank vent worked perfectly. I was able to get the tank full using the hose. I attempted to pressurize the tank by pumping the handle and the vent vented. And then the pump out hose sucked everything out and I could hear and feel the air flowing into the vent.

Glad that is working right.

And it was a beautiful day to go sailing today.

Cheers,
Jim

 

[Tom J]

Good job, and glad to hear you are out on the water! We went for a whale watch yesterday, and even though it wasn't on my boat, it just felt good to be out there, riding the swells.

 

[c130king]

Temps in the mid 50s today. 60s this weekend and nearly 70 early next week. I will be on the water 4 of the next 6 days.