Question on Odor from waste system

more than likely, what you're smelling is from the vent itself. the act of flushing sends air into the tank - it has to escape. You probably do not have a vent filter which usually controls odors from the tank.

With vacuflush nothing can vent back in the cabin! Think about it ... How could the venting air go thru the vacuum in the vac tank and hose then past the sealed ball valve!

What you describe is indeed air venting.

It may be coming in thru open portholes if so add a vent line filter

If the boat is closed then you have a vent leak at the tank. First thing to check is at the gauge sender, they often leak.

You also need to know whether or not you have vent filters. They can clog and pressurize the tank after a flush. They usually last 2 or 3 years but if they get went just once (full tank) they are shot

You might want to start with the simplest/cheapest possibility: take a quarter-inch nut driver and tighten every hose clamp between pooper and tank...bet you find some loose ones.

Also be advised that if your holding tanks are or can be properly vented so they get a good amount of fresh air into them, which means no filters on the vent lines and big vent lines, the tanks will not smell at all.

You need to encourage the growth of aerobic bacteria in the tanks. You do this by getting a good supply of fresh air into the tanks and using the correct chemicals that promote the growth of the good aerobic bacteria instead of the ones that try to kill all types bacteria.

You can also install bubblier or "air injection" systems in your tank to constantly pump fresh air into the tanks.

rid your boat of that nasty odor

I had the same problem as you on my 42' Hershine. The odor is strong, and will find it's way inside without difficulty.

If you can't find the inline filter, it's likely you don't have one. Dometic makes one, cost is around 80-90 bucks. Easy to install in many cases, you'll be glad you did. Also checking for loose clamps is good, never know what you'll find.

As far as a bubbler, a dockmate of mine has one, and all it does is put nasty odor into the air. I wouldn't waste my money.

Just be sure on an inline filter to avoid getting the tank too full. The filter is full of activated charcoal, and is shot the first time it gets wet.
I hope this helps.
Richard

I properly installed bubblier used with products that promote the growth of aerobic bacteria works just fine at eliminating holding tank odors.

If you don't believe me, perhaps you'll believe Peggie Hall:

"Sewage contains both aerobic (need oxygen to survive and thrive), and anaerobic bacteria (thrive in an airless environment); neither can function in the other's environment. Why is that important? Because only the
anaerobic bacteria in sewage produce foul-smelling gasses! Aerobic bacteria break sewage down, as does anaerobic bacteria--but aerobic bacteria do not generate odor. So as long as there is a sufficient supply of air to
the tank, and an aerobic bacteria treatment is added to aid that which naturally occurs in sewage, the aerobic bacteria thrive and overpower the anaerobic bacteria, and the system remains odor free."

The problem is many people continue to add the wrong chemicals to their tank after adding a bubblier. And the just end up defeating the purpose of the bubblier.

A huge help with this is having 2 large vents, but 1 mounted on each hull side. Then sitting at the dock you'll usually get some cross ventilation from the wind on the side of the boat. But a holding tank that has properly sized vents usually doesn't have issues with smell, whereas a holding tank with a blocked vent or very small vent will usually always have issues.

filters are usually installed as high as possible so you need to see where the vent is on the hull and check if there is an access panel inside some cabinetry, etc...

again, with all hatches and portholes CLOSED, the smell escaping outside, thru the vent, after a flush should not be smelled inside the the boat.

If you get the smell inside the boat then there is an "air/vent" leak somewhere.

clamps are obviously a good / cheap way to start, but what usually let air escape is the gauge sender. in fact, just last month i was taking a 63 footer to the bahamas and found the guage assembly (sealand tank watch) to be loose. A mechanic had replaced it and barely had it finger tight. in addition to the smell, once the tank got full, black water started leaking out.

with a vent filter, you dont' even need to worry about chemicals and vents. I never use anny

What about the hoses? Are they of the odor-safe type or worn down cheaper sanitation hoses. You might be surprised how much smell they can let trough.

If the hose-clips between pooper and vacuum tank were not tight the pump would run more frequent. As you have 2 separate systems you could compare the time it takes for the pumps to re-activate after they have build up a vacuum after a flush.

then indeed permeating hoses are not the main issue. it sounds like the typical "air" leak in the tank, gauge sender or vent line.

What is the quickest way of verifying that a vent is still open?

Find the holding tank ... remove the vent line from the holding tank ... see if it's clogged there ... you could use a piece of stainless wire to poke ... trace the vent line from there ... the clog could be at the holding tank, the line or the through hull vent fitting. You could remove the vent line from the holding tank and then blow through the tube to see is it's free ... you could put a small extension on the tube or wrap the tube as you probably don't want your mouth on that tube

You could also check the filter (which I think you said it has one) for proper installation. It's supposed to be installed so the filter is higher than the through hull if I recall. Mine was not and it would have been difficult to make that happen so I removed the in-line filter.

Remove the hose from the tank and blow it with compressed air, you could even have someone outside at the vent to listen for it. You'll know whether or not air is venting through it.

Take the holding tank deck plate cap off and blow the vent coming off of the tank into the tank and see if you feel it or hear it. I wouldn't do this for very long or you might blow waste up through the open deck plate.

Another option is to take the deck plate off, and flush the toilet. See if you hear air coming out the open deck plate, or put a paper towel over it and see if it rises. If there is no odor inside the boat, then the vent may be blocked.

I had the exact same sypmtoms that you described on my Viking. Do all the things that were described by others, like I did. But the problem was a cracked diaphragm from the vacuflush pump. It wasn't till it actually started leaking waste through the top of the pump that I found it. Rebuilt the pump and the smell is gone. Drove me crazy for a whole summer as I had done everything that was recommended by the rest of the posts. I'll betcha yours is cracked!

Hi
I did a delivery on a 68 nordhavn from hell , every time someone flushed the head the boat would fill with a "lovely" aroma
Disconecting the vent line and filter had no affect , eventually i tried a new filter problem solved ,
some filters after that lasted 2 months aothers 6 months
Totally random , worth trying a new filter